From 77da2d910a17e1e6a7e949578723d5aab58568d5 Mon Sep 17 00:00:00 2001 From: Jon Hunter Date: Sat, 27 Jun 2009 00:07:25 -0500 Subject: [PATCH] OMAP3: PM: Prevent hang in prcm_interrupt_handler There are two scenarios where a race condition could result in a hang in the prcm_interrupt handler. These are: 1). Waiting for PRM_IRQSTATUS_MPU register to clear. Bit 0 of the PRM_IRQSTATUS_MPU register indicates that a wake-up event is pending for the MPU. This bit can only be cleared if the all the wake-up events latched in the various PM_WKST_x registers have been cleared. If a wake-up event occurred during the processing of the prcm interrupt handler, after the corresponding PM_WKST_x register was checked but before the PRM_IRQSTATUS_MPU was cleared, then the CPU would be stuck forever waiting for bit 0 in PRM_IRQSTATUS_MPU to be cleared. 2). Waiting for the PM_WKST_x register to clear. Some power domains have more than one wake-up source. The PM_WKST_x registers indicate the source of a wake-up event and need to be cleared after a wake-up event occurs. When the PM_WKST_x registers are read and before they are cleared, it is possible that another wake-up event could occur causing another bit to be set in one of the PM_WKST_x registers. If this did occur after reading a PM_WKST_x register then the CPU would miss this event and get stuck forever in a loop waiting for that PM_WKST_x register to clear. This patch address the above race conditions that would result in a hang. Signed-off-by: Jon Hunter Reviewed-by: Paul Walmsley Signed-off-by: Kevin Hilman --- arch/arm/mach-omap2/pm34xx.c | 143 +++++++++++++++-------------------- 1 file changed, 60 insertions(+), 83 deletions(-) diff --git a/arch/arm/mach-omap2/pm34xx.c b/arch/arm/mach-omap2/pm34xx.c index 0ff5a6c53aa0..1e7aae2ce5ed 100644 --- a/arch/arm/mach-omap2/pm34xx.c +++ b/arch/arm/mach-omap2/pm34xx.c @@ -51,97 +51,74 @@ static void (*_omap_sram_idle)(u32 *addr, int save_state); static struct powerdomain *mpu_pwrdm; -/* PRCM Interrupt Handler for wakeups */ -static irqreturn_t prcm_interrupt_handler (int irq, void *dev_id) +/* + * PRCM Interrupt Handler Helper Function + * + * The purpose of this function is to clear any wake-up events latched + * in the PRCM PM_WKST_x registers. It is possible that a wake-up event + * may occur whilst attempting to clear a PM_WKST_x register and thus + * set another bit in this register. A while loop is used to ensure + * that any peripheral wake-up events occurring while attempting to + * clear the PM_WKST_x are detected and cleared. + */ +static void prcm_clear_mod_irqs(s16 module, u8 regs) { - u32 wkst, irqstatus_mpu; - u32 fclk, iclk; + u32 wkst, fclk, iclk; + u16 wkst_off = (regs == 3) ? OMAP3430ES2_PM_WKST3 : PM_WKST1; + u16 fclk_off = (regs == 3) ? OMAP3430ES2_CM_FCLKEN3 : CM_FCLKEN1; + u16 iclk_off = (regs == 3) ? CM_ICLKEN3 : CM_ICLKEN1; - /* WKUP */ - wkst = prm_read_mod_reg(WKUP_MOD, PM_WKST); + wkst = prm_read_mod_reg(module, wkst_off); if (wkst) { - iclk = cm_read_mod_reg(WKUP_MOD, CM_ICLKEN); - fclk = cm_read_mod_reg(WKUP_MOD, CM_FCLKEN); - cm_set_mod_reg_bits(wkst, WKUP_MOD, CM_ICLKEN); - cm_set_mod_reg_bits(wkst, WKUP_MOD, CM_FCLKEN); - prm_write_mod_reg(wkst, WKUP_MOD, PM_WKST); - while (prm_read_mod_reg(WKUP_MOD, PM_WKST)) - cpu_relax(); - cm_write_mod_reg(iclk, WKUP_MOD, CM_ICLKEN); - cm_write_mod_reg(fclk, WKUP_MOD, CM_FCLKEN); - } - - /* CORE */ - wkst = prm_read_mod_reg(CORE_MOD, PM_WKST1); - if (wkst) { - iclk = cm_read_mod_reg(CORE_MOD, CM_ICLKEN1); - fclk = cm_read_mod_reg(CORE_MOD, CM_FCLKEN1); - cm_set_mod_reg_bits(wkst, CORE_MOD, CM_ICLKEN1); - cm_set_mod_reg_bits(wkst, CORE_MOD, CM_FCLKEN1); - prm_write_mod_reg(wkst, CORE_MOD, PM_WKST1); - while (prm_read_mod_reg(CORE_MOD, PM_WKST1)) - cpu_relax(); - cm_write_mod_reg(iclk, CORE_MOD, CM_ICLKEN1); - cm_write_mod_reg(fclk, CORE_MOD, CM_FCLKEN1); - } - wkst = prm_read_mod_reg(CORE_MOD, OMAP3430ES2_PM_WKST3); - if (wkst) { - iclk = cm_read_mod_reg(CORE_MOD, CM_ICLKEN3); - fclk = cm_read_mod_reg(CORE_MOD, OMAP3430ES2_CM_FCLKEN3); - cm_set_mod_reg_bits(wkst, CORE_MOD, CM_ICLKEN3); - cm_set_mod_reg_bits(wkst, CORE_MOD, OMAP3430ES2_CM_FCLKEN3); - prm_write_mod_reg(wkst, CORE_MOD, OMAP3430ES2_PM_WKST3); - while (prm_read_mod_reg(CORE_MOD, OMAP3430ES2_PM_WKST3)) - cpu_relax(); - cm_write_mod_reg(iclk, CORE_MOD, CM_ICLKEN3); - cm_write_mod_reg(fclk, CORE_MOD, OMAP3430ES2_CM_FCLKEN3); - } - - /* PER */ - wkst = prm_read_mod_reg(OMAP3430_PER_MOD, PM_WKST); - if (wkst) { - iclk = cm_read_mod_reg(OMAP3430_PER_MOD, CM_ICLKEN); - fclk = cm_read_mod_reg(OMAP3430_PER_MOD, CM_FCLKEN); - cm_set_mod_reg_bits(wkst, OMAP3430_PER_MOD, CM_ICLKEN); - cm_set_mod_reg_bits(wkst, OMAP3430_PER_MOD, CM_FCLKEN); - prm_write_mod_reg(wkst, OMAP3430_PER_MOD, PM_WKST); - while (prm_read_mod_reg(OMAP3430_PER_MOD, PM_WKST)) - cpu_relax(); - cm_write_mod_reg(iclk, OMAP3430_PER_MOD, CM_ICLKEN); - cm_write_mod_reg(fclk, OMAP3430_PER_MOD, CM_FCLKEN); + iclk = cm_read_mod_reg(module, iclk_off); + fclk = cm_read_mod_reg(module, fclk_off); + while (wkst) { + cm_set_mod_reg_bits(wkst, module, iclk_off); + cm_set_mod_reg_bits(wkst, module, fclk_off); + prm_write_mod_reg(wkst, module, wkst_off); + wkst = prm_read_mod_reg(module, wkst_off); + } + cm_write_mod_reg(iclk, module, iclk_off); + cm_write_mod_reg(fclk, module, fclk_off); } +} - if (omap_rev() > OMAP3430_REV_ES1_0) { - /* USBHOST */ - wkst = prm_read_mod_reg(OMAP3430ES2_USBHOST_MOD, PM_WKST); - if (wkst) { - iclk = cm_read_mod_reg(OMAP3430ES2_USBHOST_MOD, - CM_ICLKEN); - fclk = cm_read_mod_reg(OMAP3430ES2_USBHOST_MOD, - CM_FCLKEN); - cm_set_mod_reg_bits(wkst, OMAP3430ES2_USBHOST_MOD, - CM_ICLKEN); - cm_set_mod_reg_bits(wkst, OMAP3430ES2_USBHOST_MOD, - CM_FCLKEN); - prm_write_mod_reg(wkst, OMAP3430ES2_USBHOST_MOD, - PM_WKST); - while (prm_read_mod_reg(OMAP3430ES2_USBHOST_MOD, - PM_WKST)) - cpu_relax(); - cm_write_mod_reg(iclk, OMAP3430ES2_USBHOST_MOD, - CM_ICLKEN); - cm_write_mod_reg(fclk, OMAP3430ES2_USBHOST_MOD, - CM_FCLKEN); +/* + * PRCM Interrupt Handler + * + * The PRM_IRQSTATUS_MPU register indicates if there are any pending + * interrupts from the PRCM for the MPU. These bits must be cleared in + * order to clear the PRCM interrupt. The PRCM interrupt handler is + * implemented to simply clear the PRM_IRQSTATUS_MPU in order to clear + * the PRCM interrupt. Please note that bit 0 of the PRM_IRQSTATUS_MPU + * register indicates that a wake-up event is pending for the MPU and + * this bit can only be cleared if the all the wake-up events latched + * in the various PM_WKST_x registers have been cleared. The interrupt + * handler is implemented using a do-while loop so that if a wake-up + * event occurred during the processing of the prcm interrupt handler + * (setting a bit in the corresponding PM_WKST_x register and thus + * preventing us from clearing bit 0 of the PRM_IRQSTATUS_MPU register) + * this would be handled. + */ +static irqreturn_t prcm_interrupt_handler (int irq, void *dev_id) +{ + u32 irqstatus_mpu; + + do { + prcm_clear_mod_irqs(WKUP_MOD, 1); + prcm_clear_mod_irqs(CORE_MOD, 1); + prcm_clear_mod_irqs(OMAP3430_PER_MOD, 1); + if (omap_rev() > OMAP3430_REV_ES1_0) { + prcm_clear_mod_irqs(CORE_MOD, 3); + prcm_clear_mod_irqs(OMAP3430ES2_USBHOST_MOD, 1); } - } - irqstatus_mpu = prm_read_mod_reg(OCP_MOD, - OMAP3_PRM_IRQSTATUS_MPU_OFFSET); - prm_write_mod_reg(irqstatus_mpu, OCP_MOD, - OMAP3_PRM_IRQSTATUS_MPU_OFFSET); + irqstatus_mpu = prm_read_mod_reg(OCP_MOD, + OMAP3_PRM_IRQSTATUS_MPU_OFFSET); + prm_write_mod_reg(irqstatus_mpu, OCP_MOD, + OMAP3_PRM_IRQSTATUS_MPU_OFFSET); - while (prm_read_mod_reg(OCP_MOD, OMAP3_PRM_IRQSTATUS_MPU_OFFSET)) - cpu_relax(); + } while (prm_read_mod_reg(OCP_MOD, OMAP3_PRM_IRQSTATUS_MPU_OFFSET)); return IRQ_HANDLED; } -- 2.34.1