Merge branch 'imx/fixes' of git://git.pengutronix.de/git/imx/linux-2.6 into fixes

[deliverable/linux.git] / drivers / mtd / nand / gpmi-nand / gpmi-lib.c

/*
 * Freescale GPMI NAND Flash Driver
 *
 * Copyright (C) 2008-2011 Freescale Semiconductor, Inc.
 * Copyright (C) 2008 Embedded Alley Solutions, Inc.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */
#include <linux/mtd/gpmi-nand.h>
#include <linux/delay.h>
#include <linux/clk.h>

#include "gpmi-nand.h"
#include "gpmi-regs.h"
#include "bch-regs.h"

struct timing_threshod timing_default_threshold = {
        .max_data_setup_cycles       = (BM_GPMI_TIMING0_DATA_SETUP >>
                                                BP_GPMI_TIMING0_DATA_SETUP),
        .internal_data_setup_in_ns   = 0,
        .max_sample_delay_factor     = (BM_GPMI_CTRL1_RDN_DELAY >>
                                                BP_GPMI_CTRL1_RDN_DELAY),
        .max_dll_clock_period_in_ns  = 32,
        .max_dll_delay_in_ns         = 16,
};

#define MXS_SET_ADDR            0x4
#define MXS_CLR_ADDR            0x8
/*
 * Clear the bit and poll it cleared.  This is usually called with
 * a reset address and mask being either SFTRST(bit 31) or CLKGATE
 * (bit 30).
 */
static int clear_poll_bit(void __iomem *addr, u32 mask)
{
        int timeout = 0x400;

        /* clear the bit */
        writel(mask, addr + MXS_CLR_ADDR);

        /*
         * SFTRST needs 3 GPMI clocks to settle, the reference manual
         * recommends to wait 1us.
         */
        udelay(1);

        /* poll the bit becoming clear */
        while ((readl(addr) & mask) && --timeout)
                /* nothing */;

        return !timeout;
}

#define MODULE_CLKGATE          (1 << 30)
#define MODULE_SFTRST           (1 << 31)
/*
 * The current mxs_reset_block() will do two things:
 *  [1] enable the module.
 *  [2] reset the module.
 *
 * In most of the cases, it's ok.
 * But in MX23, there is a hardware bug in the BCH block (see erratum #2847).
 * If you try to soft reset the BCH block, it becomes unusable until
 * the next hard reset. This case occurs in the NAND boot mode. When the board
 * boots by NAND, the ROM of the chip will initialize the BCH blocks itself.
 * So If the driver tries to reset the BCH again, the BCH will not work anymore.
 * You will see a DMA timeout in this case. The bug has been fixed
 * in the following chips, such as MX28.
 *
 * To avoid this bug, just add a new parameter `just_enable` for
 * the mxs_reset_block(), and rewrite it here.
 */
static int gpmi_reset_block(void __iomem *reset_addr, bool just_enable)
{
        int ret;
        int timeout = 0x400;

        /* clear and poll SFTRST */
        ret = clear_poll_bit(reset_addr, MODULE_SFTRST);
        if (unlikely(ret))
                goto error;

        /* clear CLKGATE */
        writel(MODULE_CLKGATE, reset_addr + MXS_CLR_ADDR);

        if (!just_enable) {
                /* set SFTRST to reset the block */
                writel(MODULE_SFTRST, reset_addr + MXS_SET_ADDR);
                udelay(1);

                /* poll CLKGATE becoming set */
                while ((!(readl(reset_addr) & MODULE_CLKGATE)) && --timeout)
                        /* nothing */;
                if (unlikely(!timeout))
                        goto error;
        }

        /* clear and poll SFTRST */
        ret = clear_poll_bit(reset_addr, MODULE_SFTRST);
        if (unlikely(ret))
                goto error;

        /* clear and poll CLKGATE */
        ret = clear_poll_bit(reset_addr, MODULE_CLKGATE);
        if (unlikely(ret))
                goto error;

        return 0;

error:
        pr_err("%s(%p): module reset timeout\n", __func__, reset_addr);
        return -ETIMEDOUT;
}

int gpmi_init(struct gpmi_nand_data *this)
{
        struct resources *r = &this->resources;
        int ret;

        ret = clk_prepare_enable(r->clock);
        if (ret)
                goto err_out;
        ret = gpmi_reset_block(r->gpmi_regs, false);
        if (ret)
                goto err_out;

        /* Choose NAND mode. */
        writel(BM_GPMI_CTRL1_GPMI_MODE, r->gpmi_regs + HW_GPMI_CTRL1_CLR);

        /* Set the IRQ polarity. */
        writel(BM_GPMI_CTRL1_ATA_IRQRDY_POLARITY,
                                r->gpmi_regs + HW_GPMI_CTRL1_SET);

        /* Disable Write-Protection. */
        writel(BM_GPMI_CTRL1_DEV_RESET, r->gpmi_regs + HW_GPMI_CTRL1_SET);

        /* Select BCH ECC. */
        writel(BM_GPMI_CTRL1_BCH_MODE, r->gpmi_regs + HW_GPMI_CTRL1_SET);

        clk_disable_unprepare(r->clock);
        return 0;
err_out:
        return ret;
}

/* This function is very useful. It is called only when the bug occur. */
void gpmi_dump_info(struct gpmi_nand_data *this)
{
        struct resources *r = &this->resources;
        struct bch_geometry *geo = &this->bch_geometry;
        u32 reg;
        int i;

        pr_err("Show GPMI registers :\n");
        for (i = 0; i <= HW_GPMI_DEBUG / 0x10 + 1; i++) {
                reg = readl(r->gpmi_regs + i * 0x10);
                pr_err("offset 0x%.3x : 0x%.8x\n", i * 0x10, reg);
        }

        /* start to print out the BCH info */
        pr_err("BCH Geometry :\n");
        pr_err("GF length              : %u\n", geo->gf_len);
        pr_err("ECC Strength           : %u\n", geo->ecc_strength);
        pr_err("Page Size in Bytes     : %u\n", geo->page_size);
        pr_err("Metadata Size in Bytes : %u\n", geo->metadata_size);
        pr_err("ECC Chunk Size in Bytes: %u\n", geo->ecc_chunk_size);
        pr_err("ECC Chunk Count        : %u\n", geo->ecc_chunk_count);
        pr_err("Payload Size in Bytes  : %u\n", geo->payload_size);
        pr_err("Auxiliary Size in Bytes: %u\n", geo->auxiliary_size);
        pr_err("Auxiliary Status Offset: %u\n", geo->auxiliary_status_offset);
        pr_err("Block Mark Byte Offset : %u\n", geo->block_mark_byte_offset);
        pr_err("Block Mark Bit Offset  : %u\n", geo->block_mark_bit_offset);
}

/* Configures the geometry for BCH.  */
int bch_set_geometry(struct gpmi_nand_data *this)
{
        struct resources *r = &this->resources;
        struct bch_geometry *bch_geo = &this->bch_geometry;
        unsigned int block_count;
        unsigned int block_size;
        unsigned int metadata_size;
        unsigned int ecc_strength;
        unsigned int page_size;
        int ret;

        if (common_nfc_set_geometry(this))
                return !0;

        block_count   = bch_geo->ecc_chunk_count - 1;
        block_size    = bch_geo->ecc_chunk_size;
        metadata_size = bch_geo->metadata_size;
        ecc_strength  = bch_geo->ecc_strength >> 1;
        page_size     = bch_geo->page_size;

        ret = clk_prepare_enable(r->clock);
        if (ret)
                goto err_out;

        /*
        * Due to erratum #2847 of the MX23, the BCH cannot be soft reset on this
        * chip, otherwise it will lock up. So we skip resetting BCH on the MX23.
        * On the other hand, the MX28 needs the reset, because one case has been
        * seen where the BCH produced ECC errors constantly after 10000
        * consecutive reboots. The latter case has not been seen on the MX23 yet,
        * still we don't know if it could happen there as well.
        */
        ret = gpmi_reset_block(r->bch_regs, GPMI_IS_MX23(this));
        if (ret)
                goto err_out;

        /* Configure layout 0. */
        writel(BF_BCH_FLASH0LAYOUT0_NBLOCKS(block_count)
                        | BF_BCH_FLASH0LAYOUT0_META_SIZE(metadata_size)
                        | BF_BCH_FLASH0LAYOUT0_ECC0(ecc_strength, this)
                        | BF_BCH_FLASH0LAYOUT0_DATA0_SIZE(block_size, this),
                        r->bch_regs + HW_BCH_FLASH0LAYOUT0);

        writel(BF_BCH_FLASH0LAYOUT1_PAGE_SIZE(page_size)
                        | BF_BCH_FLASH0LAYOUT1_ECCN(ecc_strength, this)
                        | BF_BCH_FLASH0LAYOUT1_DATAN_SIZE(block_size, this),
                        r->bch_regs + HW_BCH_FLASH0LAYOUT1);

        /* Set *all* chip selects to use layout 0. */
        writel(0, r->bch_regs + HW_BCH_LAYOUTSELECT);

        /* Enable interrupts. */
        writel(BM_BCH_CTRL_COMPLETE_IRQ_EN,
                                r->bch_regs + HW_BCH_CTRL_SET);

        clk_disable_unprepare(r->clock);
        return 0;
err_out:
        return ret;
}

/* Converts time in nanoseconds to cycles. */
static unsigned int ns_to_cycles(unsigned int time,
                        unsigned int period, unsigned int min)
{
        unsigned int k;

        k = (time + period - 1) / period;
        return max(k, min);
}

#define DEF_MIN_PROP_DELAY      5
#define DEF_MAX_PROP_DELAY      9
/* Apply timing to current hardware conditions. */
static int gpmi_nfc_compute_hardware_timing(struct gpmi_nand_data *this,
                                        struct gpmi_nfc_hardware_timing *hw)
{
        struct timing_threshod *nfc = &timing_default_threshold;
        struct nand_chip *nand = &this->nand;
        struct nand_timing target = this->timing;
        bool improved_timing_is_available;
        unsigned long clock_frequency_in_hz;
        unsigned int clock_period_in_ns;
        bool dll_use_half_periods;
        unsigned int dll_delay_shift;
        unsigned int max_sample_delay_in_ns;
        unsigned int address_setup_in_cycles;
        unsigned int data_setup_in_ns;
        unsigned int data_setup_in_cycles;
        unsigned int data_hold_in_cycles;
        int ideal_sample_delay_in_ns;
        unsigned int sample_delay_factor;
        int tEYE;
        unsigned int min_prop_delay_in_ns = DEF_MIN_PROP_DELAY;
        unsigned int max_prop_delay_in_ns = DEF_MAX_PROP_DELAY;

        /*
         * If there are multiple chips, we need to relax the timings to allow
         * for signal distortion due to higher capacitance.
         */
        if (nand->numchips > 2) {
                target.data_setup_in_ns    += 10;
                target.data_hold_in_ns     += 10;
                target.address_setup_in_ns += 10;
        } else if (nand->numchips > 1) {
                target.data_setup_in_ns    += 5;
                target.data_hold_in_ns     += 5;
                target.address_setup_in_ns += 5;
        }

        /* Check if improved timing information is available. */
        improved_timing_is_available =
                (target.tREA_in_ns  >= 0) &&
                (target.tRLOH_in_ns >= 0) &&
                (target.tRHOH_in_ns >= 0) ;

        /* Inspect the clock. */
        clock_frequency_in_hz = nfc->clock_frequency_in_hz;
        clock_period_in_ns    = 1000000000 / clock_frequency_in_hz;

        /*
         * The NFC quantizes setup and hold parameters in terms of clock cycles.
         * Here, we quantize the setup and hold timing parameters to the
         * next-highest clock period to make sure we apply at least the
         * specified times.
         *
         * For data setup and data hold, the hardware interprets a value of zero
         * as the largest possible delay. This is not what's intended by a zero
         * in the input parameter, so we impose a minimum of one cycle.
         */
        data_setup_in_cycles    = ns_to_cycles(target.data_setup_in_ns,
                                                        clock_period_in_ns, 1);
        data_hold_in_cycles     = ns_to_cycles(target.data_hold_in_ns,
                                                        clock_period_in_ns, 1);
        address_setup_in_cycles = ns_to_cycles(target.address_setup_in_ns,
                                                        clock_period_in_ns, 0);

        /*
         * The clock's period affects the sample delay in a number of ways:
         *
         * (1) The NFC HAL tells us the maximum clock period the sample delay
         *     DLL can tolerate. If the clock period is greater than half that
         *     maximum, we must configure the DLL to be driven by half periods.
         *
         * (2) We need to convert from an ideal sample delay, in ns, to a
         *     "sample delay factor," which the NFC uses. This factor depends on
         *     whether we're driving the DLL with full or half periods.
         *     Paraphrasing the reference manual:
         *
         *         AD = SDF x 0.125 x RP
         *
         * where:
         *
         *     AD   is the applied delay, in ns.
         *     SDF  is the sample delay factor, which is dimensionless.
         *     RP   is the reference period, in ns, which is a full clock period
         *          if the DLL is being driven by full periods, or half that if
         *          the DLL is being driven by half periods.
         *
         * Let's re-arrange this in a way that's more useful to us:
         *
         *                        8
         *         SDF  =  AD x ----
         *                       RP
         *
         * The reference period is either the clock period or half that, so this
         * is:
         *
         *                        8       AD x DDF
         *         SDF  =  AD x -----  =  --------
         *                      f x P        P
         *
         * where:
         *
         *       f  is 1 or 1/2, depending on how we're driving the DLL.
         *       P  is the clock period.
         *     DDF  is the DLL Delay Factor, a dimensionless value that
         *          incorporates all the constants in the conversion.
         *
         * DDF will be either 8 or 16, both of which are powers of two. We can
         * reduce the cost of this conversion by using bit shifts instead of
         * multiplication or division. Thus:
         *
         *                 AD << DDS
         *         SDF  =  ---------
         *                     P
         *
         *     or
         *
         *         AD  =  (SDF >> DDS) x P
         *
         * where:
         *
         *     DDS  is the DLL Delay Shift, the logarithm to base 2 of the DDF.
         */
        if (clock_period_in_ns > (nfc->max_dll_clock_period_in_ns >> 1)) {
                dll_use_half_periods = true;
                dll_delay_shift      = 3 + 1;
        } else {
                dll_use_half_periods = false;
                dll_delay_shift      = 3;
        }

        /*
         * Compute the maximum sample delay the NFC allows, under current
         * conditions. If the clock is running too slowly, no sample delay is
         * possible.
         */
        if (clock_period_in_ns > nfc->max_dll_clock_period_in_ns)
                max_sample_delay_in_ns = 0;
        else {
                /*
                 * Compute the delay implied by the largest sample delay factor
                 * the NFC allows.
                 */
                max_sample_delay_in_ns =
                        (nfc->max_sample_delay_factor * clock_period_in_ns) >>
                                                                dll_delay_shift;

                /*
                 * Check if the implied sample delay larger than the NFC
                 * actually allows.
                 */
                if (max_sample_delay_in_ns > nfc->max_dll_delay_in_ns)
                        max_sample_delay_in_ns = nfc->max_dll_delay_in_ns;
        }

        /*
         * Check if improved timing information is available. If not, we have to
         * use a less-sophisticated algorithm.
         */
        if (!improved_timing_is_available) {
                /*
                 * Fold the read setup time required by the NFC into the ideal
                 * sample delay.
                 */
                ideal_sample_delay_in_ns = target.gpmi_sample_delay_in_ns +
                                                nfc->internal_data_setup_in_ns;

                /*
                 * The ideal sample delay may be greater than the maximum
                 * allowed by the NFC. If so, we can trade off sample delay time
                 * for more data setup time.
                 *
                 * In each iteration of the following loop, we add a cycle to
                 * the data setup time and subtract a corresponding amount from
                 * the sample delay until we've satisified the constraints or
                 * can't do any better.
                 */
                while ((ideal_sample_delay_in_ns > max_sample_delay_in_ns) &&
                        (data_setup_in_cycles < nfc->max_data_setup_cycles)) {

                        data_setup_in_cycles++;
                        ideal_sample_delay_in_ns -= clock_period_in_ns;

                        if (ideal_sample_delay_in_ns < 0)
                                ideal_sample_delay_in_ns = 0;

                }

                /*
                 * Compute the sample delay factor that corresponds most closely
                 * to the ideal sample delay. If the result is too large for the
                 * NFC, use the maximum value.
                 *
                 * Notice that we use the ns_to_cycles function to compute the
                 * sample delay factor. We do this because the form of the
                 * computation is the same as that for calculating cycles.
                 */
                sample_delay_factor =
                        ns_to_cycles(
                                ideal_sample_delay_in_ns << dll_delay_shift,
                                                        clock_period_in_ns, 0);

                if (sample_delay_factor > nfc->max_sample_delay_factor)
                        sample_delay_factor = nfc->max_sample_delay_factor;

                /* Skip to the part where we return our results. */
                goto return_results;
        }

        /*
         * If control arrives here, we have more detailed timing information,
         * so we can use a better algorithm.
         */

        /*
         * Fold the read setup time required by the NFC into the maximum
         * propagation delay.
         */
        max_prop_delay_in_ns += nfc->internal_data_setup_in_ns;

        /*
         * Earlier, we computed the number of clock cycles required to satisfy
         * the data setup time. Now, we need to know the actual nanoseconds.
         */
        data_setup_in_ns = clock_period_in_ns * data_setup_in_cycles;

        /*
         * Compute tEYE, the width of the data eye when reading from the NAND
         * Flash. The eye width is fundamentally determined by the data setup
         * time, perturbed by propagation delays and some characteristics of the
         * NAND Flash device.
         *
         * start of the eye = max_prop_delay + tREA
         * end of the eye   = min_prop_delay + tRHOH + data_setup
         */
        tEYE = (int)min_prop_delay_in_ns + (int)target.tRHOH_in_ns +
                                                        (int)data_setup_in_ns;

        tEYE -= (int)max_prop_delay_in_ns + (int)target.tREA_in_ns;

        /*
         * The eye must be open. If it's not, we can try to open it by
         * increasing its main forcer, the data setup time.
         *
         * In each iteration of the following loop, we increase the data setup
         * time by a single clock cycle. We do this until either the eye is
         * open or we run into NFC limits.
         */
        while ((tEYE <= 0) &&
                        (data_setup_in_cycles < nfc->max_data_setup_cycles)) {
                /* Give a cycle to data setup. */
                data_setup_in_cycles++;
                /* Synchronize the data setup time with the cycles. */
                data_setup_in_ns += clock_period_in_ns;
                /* Adjust tEYE accordingly. */
                tEYE += clock_period_in_ns;
        }

        /*
         * When control arrives here, the eye is open. The ideal time to sample
         * the data is in the center of the eye:
         *
         *     end of the eye + start of the eye
         *     ---------------------------------  -  data_setup
         *                    2
         *
         * After some algebra, this simplifies to the code immediately below.
         */
        ideal_sample_delay_in_ns =
                ((int)max_prop_delay_in_ns +
                        (int)target.tREA_in_ns +
                                (int)min_prop_delay_in_ns +
                                        (int)target.tRHOH_in_ns -
                                                (int)data_setup_in_ns) >> 1;

        /*
         * The following figure illustrates some aspects of a NAND Flash read:
         *
         *
         *           __                   _____________________________________
         * RDN         \_________________/
         *
         *                                         <---- tEYE ----->
         *                                        /-----------------\
         * Read Data ----------------------------<                   >---------
         *                                        \-----------------/
         *             ^                 ^                 ^              ^
         *             |                 |                 |              |
         *             |<--Data Setup -->|<--Delay Time -->|              |
         *             |                 |                 |              |
         *             |                 |                                |
         *             |                 |<--   Quantized Delay Time   -->|
         *             |                 |                                |
         *
         *
         * We have some issues we must now address:
         *
         * (1) The *ideal* sample delay time must not be negative. If it is, we
         *     jam it to zero.
         *
         * (2) The *ideal* sample delay time must not be greater than that
         *     allowed by the NFC. If it is, we can increase the data setup
         *     time, which will reduce the delay between the end of the data
         *     setup and the center of the eye. It will also make the eye
         *     larger, which might help with the next issue...
         *
         * (3) The *quantized* sample delay time must not fall either before the
         *     eye opens or after it closes (the latter is the problem
         *     illustrated in the above figure).
         */

        /* Jam a negative ideal sample delay to zero. */
        if (ideal_sample_delay_in_ns < 0)
                ideal_sample_delay_in_ns = 0;

        /*
         * Extend the data setup as needed to reduce the ideal sample delay
         * below the maximum permitted by the NFC.
         */
        while ((ideal_sample_delay_in_ns > max_sample_delay_in_ns) &&
                        (data_setup_in_cycles < nfc->max_data_setup_cycles)) {

                /* Give a cycle to data setup. */
                data_setup_in_cycles++;
                /* Synchronize the data setup time with the cycles. */
                data_setup_in_ns += clock_period_in_ns;
                /* Adjust tEYE accordingly. */
                tEYE += clock_period_in_ns;

                /*
                 * Decrease the ideal sample delay by one half cycle, to keep it
                 * in the middle of the eye.
                 */
                ideal_sample_delay_in_ns -= (clock_period_in_ns >> 1);

                /* Jam a negative ideal sample delay to zero. */
                if (ideal_sample_delay_in_ns < 0)
                        ideal_sample_delay_in_ns = 0;
        }

        /*
         * Compute the sample delay factor that corresponds to the ideal sample
         * delay. If the result is too large, then use the maximum allowed
         * value.
         *
         * Notice that we use the ns_to_cycles function to compute the sample
         * delay factor. We do this because the form of the computation is the
         * same as that for calculating cycles.
         */
        sample_delay_factor =
                ns_to_cycles(ideal_sample_delay_in_ns << dll_delay_shift,
                                                        clock_period_in_ns, 0);

        if (sample_delay_factor > nfc->max_sample_delay_factor)
                sample_delay_factor = nfc->max_sample_delay_factor;

        /*
         * These macros conveniently encapsulate a computation we'll use to
         * continuously evaluate whether or not the data sample delay is inside
         * the eye.
         */
        #define IDEAL_DELAY  ((int) ideal_sample_delay_in_ns)

        #define QUANTIZED_DELAY  \
                ((int) ((sample_delay_factor * clock_period_in_ns) >> \
                                                        dll_delay_shift))

        #define DELAY_ERROR  (abs(QUANTIZED_DELAY - IDEAL_DELAY))

        #define SAMPLE_IS_NOT_WITHIN_THE_EYE  (DELAY_ERROR > (tEYE >> 1))

        /*
         * While the quantized sample time falls outside the eye, reduce the
         * sample delay or extend the data setup to move the sampling point back
         * toward the eye. Do not allow the number of data setup cycles to
         * exceed the maximum allowed by the NFC.
         */
        while (SAMPLE_IS_NOT_WITHIN_THE_EYE &&
                        (data_setup_in_cycles < nfc->max_data_setup_cycles)) {
                /*
                 * If control arrives here, the quantized sample delay falls
                 * outside the eye. Check if it's before the eye opens, or after
                 * the eye closes.
                 */
                if (QUANTIZED_DELAY > IDEAL_DELAY) {
                        /*
                         * If control arrives here, the quantized sample delay
                         * falls after the eye closes. Decrease the quantized
                         * delay time and then go back to re-evaluate.
                         */
                        if (sample_delay_factor != 0)
                                sample_delay_factor--;
                        continue;
                }

                /*
                 * If control arrives here, the quantized sample delay falls
                 * before the eye opens. Shift the sample point by increasing
                 * data setup time. This will also make the eye larger.
                 */

                /* Give a cycle to data setup. */
                data_setup_in_cycles++;
                /* Synchronize the data setup time with the cycles. */
                data_setup_in_ns += clock_period_in_ns;
                /* Adjust tEYE accordingly. */
                tEYE += clock_period_in_ns;

                /*
                 * Decrease the ideal sample delay by one half cycle, to keep it
                 * in the middle of the eye.
                 */
                ideal_sample_delay_in_ns -= (clock_period_in_ns >> 1);

                /* ...and one less period for the delay time. */
                ideal_sample_delay_in_ns -= clock_period_in_ns;

                /* Jam a negative ideal sample delay to zero. */
                if (ideal_sample_delay_in_ns < 0)
                        ideal_sample_delay_in_ns = 0;

                /*
                 * We have a new ideal sample delay, so re-compute the quantized
                 * delay.
                 */
                sample_delay_factor =
                        ns_to_cycles(
                                ideal_sample_delay_in_ns << dll_delay_shift,
                                                        clock_period_in_ns, 0);

                if (sample_delay_factor > nfc->max_sample_delay_factor)
                        sample_delay_factor = nfc->max_sample_delay_factor;
        }

        /* Control arrives here when we're ready to return our results. */
return_results:
        hw->data_setup_in_cycles    = data_setup_in_cycles;
        hw->data_hold_in_cycles     = data_hold_in_cycles;
        hw->address_setup_in_cycles = address_setup_in_cycles;
        hw->use_half_periods        = dll_use_half_periods;
        hw->sample_delay_factor     = sample_delay_factor;

        /* Return success. */
        return 0;
}

/* Begin the I/O */
void gpmi_begin(struct gpmi_nand_data *this)
{
        struct resources *r = &this->resources;
        struct timing_threshod *nfc = &timing_default_threshold;
        unsigned char  *gpmi_regs = r->gpmi_regs;
        unsigned int   clock_period_in_ns;
        uint32_t       reg;
        unsigned int   dll_wait_time_in_us;
        struct gpmi_nfc_hardware_timing  hw;
        int ret;

        /* Enable the clock. */
        ret = clk_prepare_enable(r->clock);
        if (ret) {
                pr_err("We failed in enable the clk\n");
                goto err_out;
        }

        /* set ready/busy timeout */
        writel(0x500 << BP_GPMI_TIMING1_BUSY_TIMEOUT,
                gpmi_regs + HW_GPMI_TIMING1);

        /* Get the timing information we need. */
        nfc->clock_frequency_in_hz = clk_get_rate(r->clock);
        clock_period_in_ns = 1000000000 / nfc->clock_frequency_in_hz;

        gpmi_nfc_compute_hardware_timing(this, &hw);

        /* Set up all the simple timing parameters. */
        reg = BF_GPMI_TIMING0_ADDRESS_SETUP(hw.address_setup_in_cycles) |
                BF_GPMI_TIMING0_DATA_HOLD(hw.data_hold_in_cycles)         |
                BF_GPMI_TIMING0_DATA_SETUP(hw.data_setup_in_cycles)       ;

        writel(reg, gpmi_regs + HW_GPMI_TIMING0);

        /*
         * DLL_ENABLE must be set to 0 when setting RDN_DELAY or HALF_PERIOD.
         */
        writel(BM_GPMI_CTRL1_DLL_ENABLE, gpmi_regs + HW_GPMI_CTRL1_CLR);

        /* Clear out the DLL control fields. */
        writel(BM_GPMI_CTRL1_RDN_DELAY,   gpmi_regs + HW_GPMI_CTRL1_CLR);
        writel(BM_GPMI_CTRL1_HALF_PERIOD, gpmi_regs + HW_GPMI_CTRL1_CLR);

        /* If no sample delay is called for, return immediately. */
        if (!hw.sample_delay_factor)
                return;

        /* Configure the HALF_PERIOD flag. */
        if (hw.use_half_periods)
                writel(BM_GPMI_CTRL1_HALF_PERIOD,
                                                gpmi_regs + HW_GPMI_CTRL1_SET);

        /* Set the delay factor. */
        writel(BF_GPMI_CTRL1_RDN_DELAY(hw.sample_delay_factor),
                                                gpmi_regs + HW_GPMI_CTRL1_SET);

        /* Enable the DLL. */
        writel(BM_GPMI_CTRL1_DLL_ENABLE, gpmi_regs + HW_GPMI_CTRL1_SET);

        /*
         * After we enable the GPMI DLL, we have to wait 64 clock cycles before
         * we can use the GPMI.
         *
         * Calculate the amount of time we need to wait, in microseconds.
         */
        dll_wait_time_in_us = (clock_period_in_ns * 64) / 1000;

        if (!dll_wait_time_in_us)
                dll_wait_time_in_us = 1;

        /* Wait for the DLL to settle. */
        udelay(dll_wait_time_in_us);

err_out:
        return;
}

void gpmi_end(struct gpmi_nand_data *this)
{
        struct resources *r = &this->resources;
        clk_disable_unprepare(r->clock);
}

/* Clears a BCH interrupt. */
void gpmi_clear_bch(struct gpmi_nand_data *this)
{
        struct resources *r = &this->resources;
        writel(BM_BCH_CTRL_COMPLETE_IRQ, r->bch_regs + HW_BCH_CTRL_CLR);
}

/* Returns the Ready/Busy status of the given chip. */
int gpmi_is_ready(struct gpmi_nand_data *this, unsigned chip)
{
        struct resources *r = &this->resources;
        uint32_t mask = 0;
        uint32_t reg = 0;

        if (GPMI_IS_MX23(this)) {
                mask = MX23_BM_GPMI_DEBUG_READY0 << chip;
                reg = readl(r->gpmi_regs + HW_GPMI_DEBUG);
        } else if (GPMI_IS_MX28(this) || GPMI_IS_MX6Q(this)) {
                /* MX28 shares the same R/B register as MX6Q. */
                mask = MX28_BF_GPMI_STAT_READY_BUSY(1 << chip);
                reg = readl(r->gpmi_regs + HW_GPMI_STAT);
        } else
                pr_err("unknow arch.\n");
        return reg & mask;
}

static inline void set_dma_type(struct gpmi_nand_data *this,
                                        enum dma_ops_type type)
{
        this->last_dma_type = this->dma_type;
        this->dma_type = type;
}

int gpmi_send_command(struct gpmi_nand_data *this)
{
        struct dma_chan *channel = get_dma_chan(this);
        struct dma_async_tx_descriptor *desc;
        struct scatterlist *sgl;
        int chip = this->current_chip;
        u32 pio[3];

        /* [1] send out the PIO words */
        pio[0] = BF_GPMI_CTRL0_COMMAND_MODE(BV_GPMI_CTRL0_COMMAND_MODE__WRITE)
                | BM_GPMI_CTRL0_WORD_LENGTH
                | BF_GPMI_CTRL0_CS(chip, this)
                | BF_GPMI_CTRL0_LOCK_CS(LOCK_CS_ENABLE, this)
                | BF_GPMI_CTRL0_ADDRESS(BV_GPMI_CTRL0_ADDRESS__NAND_CLE)
                | BM_GPMI_CTRL0_ADDRESS_INCREMENT
                | BF_GPMI_CTRL0_XFER_COUNT(this->command_length);
        pio[1] = pio[2] = 0;
        desc = dmaengine_prep_slave_sg(channel,
                                        (struct scatterlist *)pio,
                                        ARRAY_SIZE(pio), DMA_TRANS_NONE, 0);
        if (!desc) {
                pr_err("step 1 error\n");
                return -1;
        }

        /* [2] send out the COMMAND + ADDRESS string stored in @buffer */
        sgl = &this->cmd_sgl;

        sg_init_one(sgl, this->cmd_buffer, this->command_length);
        dma_map_sg(this->dev, sgl, 1, DMA_TO_DEVICE);
        desc = dmaengine_prep_slave_sg(channel,
                                sgl, 1, DMA_MEM_TO_DEV,
                                DMA_PREP_INTERRUPT | DMA_CTRL_ACK);

        if (!desc) {
                pr_err("step 2 error\n");
                return -1;
        }

        /* [3] submit the DMA */
        set_dma_type(this, DMA_FOR_COMMAND);
        return start_dma_without_bch_irq(this, desc);
}

int gpmi_send_data(struct gpmi_nand_data *this)
{
        struct dma_async_tx_descriptor *desc;
        struct dma_chan *channel = get_dma_chan(this);
        int chip = this->current_chip;
        uint32_t command_mode;
        uint32_t address;
        u32 pio[2];

        /* [1] PIO */
        command_mode = BV_GPMI_CTRL0_COMMAND_MODE__WRITE;
        address      = BV_GPMI_CTRL0_ADDRESS__NAND_DATA;

        pio[0] = BF_GPMI_CTRL0_COMMAND_MODE(command_mode)
                | BM_GPMI_CTRL0_WORD_LENGTH
                | BF_GPMI_CTRL0_CS(chip, this)
                | BF_GPMI_CTRL0_LOCK_CS(LOCK_CS_ENABLE, this)
                | BF_GPMI_CTRL0_ADDRESS(address)
                | BF_GPMI_CTRL0_XFER_COUNT(this->upper_len);
        pio[1] = 0;
        desc = dmaengine_prep_slave_sg(channel, (struct scatterlist *)pio,
                                        ARRAY_SIZE(pio), DMA_TRANS_NONE, 0);
        if (!desc) {
                pr_err("step 1 error\n");
                return -1;
        }

        /* [2] send DMA request */
        prepare_data_dma(this, DMA_TO_DEVICE);
        desc = dmaengine_prep_slave_sg(channel, &this->data_sgl,
                                        1, DMA_MEM_TO_DEV,
                                        DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
        if (!desc) {
                pr_err("step 2 error\n");
                return -1;
        }
        /* [3] submit the DMA */
        set_dma_type(this, DMA_FOR_WRITE_DATA);
        return start_dma_without_bch_irq(this, desc);
}

int gpmi_read_data(struct gpmi_nand_data *this)
{
        struct dma_async_tx_descriptor *desc;
        struct dma_chan *channel = get_dma_chan(this);
        int chip = this->current_chip;
        u32 pio[2];

        /* [1] : send PIO */
        pio[0] = BF_GPMI_CTRL0_COMMAND_MODE(BV_GPMI_CTRL0_COMMAND_MODE__READ)
                | BM_GPMI_CTRL0_WORD_LENGTH
                | BF_GPMI_CTRL0_CS(chip, this)
                | BF_GPMI_CTRL0_LOCK_CS(LOCK_CS_ENABLE, this)
                | BF_GPMI_CTRL0_ADDRESS(BV_GPMI_CTRL0_ADDRESS__NAND_DATA)
                | BF_GPMI_CTRL0_XFER_COUNT(this->upper_len);
        pio[1] = 0;
        desc = dmaengine_prep_slave_sg(channel,
                                        (struct scatterlist *)pio,
                                        ARRAY_SIZE(pio), DMA_TRANS_NONE, 0);
        if (!desc) {
                pr_err("step 1 error\n");
                return -1;
        }

        /* [2] : send DMA request */
        prepare_data_dma(this, DMA_FROM_DEVICE);
        desc = dmaengine_prep_slave_sg(channel, &this->data_sgl,
                                        1, DMA_DEV_TO_MEM,
                                        DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
        if (!desc) {
                pr_err("step 2 error\n");
                return -1;
        }

        /* [3] : submit the DMA */
        set_dma_type(this, DMA_FOR_READ_DATA);
        return start_dma_without_bch_irq(this, desc);
}

int gpmi_send_page(struct gpmi_nand_data *this,
                        dma_addr_t payload, dma_addr_t auxiliary)
{
        struct bch_geometry *geo = &this->bch_geometry;
        uint32_t command_mode;
        uint32_t address;
        uint32_t ecc_command;
        uint32_t buffer_mask;
        struct dma_async_tx_descriptor *desc;
        struct dma_chan *channel = get_dma_chan(this);
        int chip = this->current_chip;
        u32 pio[6];

        /* A DMA descriptor that does an ECC page read. */
        command_mode = BV_GPMI_CTRL0_COMMAND_MODE__WRITE;
        address      = BV_GPMI_CTRL0_ADDRESS__NAND_DATA;
        ecc_command  = BV_GPMI_ECCCTRL_ECC_CMD__BCH_ENCODE;
        buffer_mask  = BV_GPMI_ECCCTRL_BUFFER_MASK__BCH_PAGE |
                                BV_GPMI_ECCCTRL_BUFFER_MASK__BCH_AUXONLY;

        pio[0] = BF_GPMI_CTRL0_COMMAND_MODE(command_mode)
                | BM_GPMI_CTRL0_WORD_LENGTH
                | BF_GPMI_CTRL0_CS(chip, this)
                | BF_GPMI_CTRL0_LOCK_CS(LOCK_CS_ENABLE, this)
                | BF_GPMI_CTRL0_ADDRESS(address)
                | BF_GPMI_CTRL0_XFER_COUNT(0);
        pio[1] = 0;
        pio[2] = BM_GPMI_ECCCTRL_ENABLE_ECC
                | BF_GPMI_ECCCTRL_ECC_CMD(ecc_command)
                | BF_GPMI_ECCCTRL_BUFFER_MASK(buffer_mask);
        pio[3] = geo->page_size;
        pio[4] = payload;
        pio[5] = auxiliary;

        desc = dmaengine_prep_slave_sg(channel,
                                        (struct scatterlist *)pio,
                                        ARRAY_SIZE(pio), DMA_TRANS_NONE,
                                        DMA_CTRL_ACK);
        if (!desc) {
                pr_err("step 2 error\n");
                return -1;
        }
        set_dma_type(this, DMA_FOR_WRITE_ECC_PAGE);
        return start_dma_with_bch_irq(this, desc);
}

int gpmi_read_page(struct gpmi_nand_data *this,
                                dma_addr_t payload, dma_addr_t auxiliary)
{
        struct bch_geometry *geo = &this->bch_geometry;
        uint32_t command_mode;
        uint32_t address;
        uint32_t ecc_command;
        uint32_t buffer_mask;
        struct dma_async_tx_descriptor *desc;
        struct dma_chan *channel = get_dma_chan(this);
        int chip = this->current_chip;
        u32 pio[6];

        /* [1] Wait for the chip to report ready. */
        command_mode = BV_GPMI_CTRL0_COMMAND_MODE__WAIT_FOR_READY;
        address      = BV_GPMI_CTRL0_ADDRESS__NAND_DATA;

        pio[0] =  BF_GPMI_CTRL0_COMMAND_MODE(command_mode)
                | BM_GPMI_CTRL0_WORD_LENGTH
                | BF_GPMI_CTRL0_CS(chip, this)
                | BF_GPMI_CTRL0_LOCK_CS(LOCK_CS_ENABLE, this)
                | BF_GPMI_CTRL0_ADDRESS(address)
                | BF_GPMI_CTRL0_XFER_COUNT(0);
        pio[1] = 0;
        desc = dmaengine_prep_slave_sg(channel,
                                (struct scatterlist *)pio, 2,
                                DMA_TRANS_NONE, 0);
        if (!desc) {
                pr_err("step 1 error\n");
                return -1;
        }

        /* [2] Enable the BCH block and read. */
        command_mode = BV_GPMI_CTRL0_COMMAND_MODE__READ;
        address      = BV_GPMI_CTRL0_ADDRESS__NAND_DATA;
        ecc_command  = BV_GPMI_ECCCTRL_ECC_CMD__BCH_DECODE;
        buffer_mask  = BV_GPMI_ECCCTRL_BUFFER_MASK__BCH_PAGE
                        | BV_GPMI_ECCCTRL_BUFFER_MASK__BCH_AUXONLY;

        pio[0] =  BF_GPMI_CTRL0_COMMAND_MODE(command_mode)
                | BM_GPMI_CTRL0_WORD_LENGTH
                | BF_GPMI_CTRL0_CS(chip, this)
                | BF_GPMI_CTRL0_LOCK_CS(LOCK_CS_ENABLE, this)
                | BF_GPMI_CTRL0_ADDRESS(address)
                | BF_GPMI_CTRL0_XFER_COUNT(geo->page_size);

        pio[1] = 0;
        pio[2] =  BM_GPMI_ECCCTRL_ENABLE_ECC
                | BF_GPMI_ECCCTRL_ECC_CMD(ecc_command)
                | BF_GPMI_ECCCTRL_BUFFER_MASK(buffer_mask);
        pio[3] = geo->page_size;
        pio[4] = payload;
        pio[5] = auxiliary;
        desc = dmaengine_prep_slave_sg(channel,
                                        (struct scatterlist *)pio,
                                        ARRAY_SIZE(pio), DMA_TRANS_NONE,
                                        DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
        if (!desc) {
                pr_err("step 2 error\n");
                return -1;
        }

        /* [3] Disable the BCH block */
        command_mode = BV_GPMI_CTRL0_COMMAND_MODE__WAIT_FOR_READY;
        address      = BV_GPMI_CTRL0_ADDRESS__NAND_DATA;

        pio[0] = BF_GPMI_CTRL0_COMMAND_MODE(command_mode)
                | BM_GPMI_CTRL0_WORD_LENGTH
                | BF_GPMI_CTRL0_CS(chip, this)
                | BF_GPMI_CTRL0_LOCK_CS(LOCK_CS_ENABLE, this)
                | BF_GPMI_CTRL0_ADDRESS(address)
                | BF_GPMI_CTRL0_XFER_COUNT(geo->page_size);
        pio[1] = 0;
        pio[2] = 0; /* clear GPMI_HW_GPMI_ECCCTRL, disable the BCH. */
        desc = dmaengine_prep_slave_sg(channel,
                                (struct scatterlist *)pio, 3,
                                DMA_TRANS_NONE,
                                DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
        if (!desc) {
                pr_err("step 3 error\n");
                return -1;
        }

        /* [4] submit the DMA */
        set_dma_type(this, DMA_FOR_READ_ECC_PAGE);
        return start_dma_with_bch_irq(this, desc);
}