arch/powerpc/platforms/powernv/opal-msglog.c

   1 /*
   2  * PowerNV OPAL in-memory console interface
   3  *
   4  * Copyright 2014 IBM Corp.
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the License, or (at your option) any later version.
  10  */
  11
  12 #include <asm/io.h>
  13 #include <asm/opal.h>
  14 #include <linux/debugfs.h>
  15 #include <linux/of.h>
  16 #include <linux/types.h>
  17 #include <asm/barrier.h>
  18
  19 /* OPAL in-memory console. Defined in OPAL source at core/console.c */
  20 struct memcons {
  21         __be64 magic;
  22 #define MEMCONS_MAGIC   0x6630696567726173L
  23         __be64 obuf_phys;
  24         __be64 ibuf_phys;
  25         __be32 obuf_size;
  26         __be32 ibuf_size;
  27         __be32 out_pos;
  28 #define MEMCONS_OUT_POS_WRAP    0x80000000u
  29 #define MEMCONS_OUT_POS_MASK    0x00ffffffu
  30         __be32 in_prod;
  31         __be32 in_cons;
  32 };
  33
  34 static struct memcons *opal_memcons = NULL;
  35
  36 ssize_t opal_msglog_copy(char *to, loff_t pos, size_t count)
  37 {
  38         const char *conbuf;
  39         ssize_t ret;
  40         size_t first_read = 0;
  41         uint32_t out_pos, avail;
  42
  43         if (!opal_memcons)
  44                 return -ENODEV;
  45
  46         out_pos = be32_to_cpu(ACCESS_ONCE(opal_memcons->out_pos));
  47
  48         /* Now we've read out_pos, put a barrier in before reading the new
  49          * data it points to in conbuf. */
  50         smp_rmb();
  51
  52         conbuf = phys_to_virt(be64_to_cpu(opal_memcons->obuf_phys));
  53
  54         /* When the buffer has wrapped, read from the out_pos marker to the end
  55          * of the buffer, and then read the remaining data as in the un-wrapped
  56          * case. */
  57         if (out_pos & MEMCONS_OUT_POS_WRAP) {
  58
  59                 out_pos &= MEMCONS_OUT_POS_MASK;
  60                 avail = be32_to_cpu(opal_memcons->obuf_size) - out_pos;
  61
  62                 ret = memory_read_from_buffer(to, count, &pos,
  63                                 conbuf + out_pos, avail);
  64
  65                 if (ret < 0)
  66                         goto out;
  67
  68                 first_read = ret;
  69                 to += first_read;
  70                 count -= first_read;
  71                 pos -= avail;
  72
  73                 if (count <= 0)
  74                         goto out;
  75         }
  76
  77         /* Sanity check. The firmware should not do this to us. */
  78         if (out_pos > be32_to_cpu(opal_memcons->obuf_size)) {
  79                 pr_err("OPAL: memory console corruption. Aborting read.\n");
  80                 return -EINVAL;
  81         }
  82
  83         ret = memory_read_from_buffer(to, count, &pos, conbuf, out_pos);
  84
  85         if (ret < 0)
  86                 goto out;
  87
  88         ret += first_read;
  89 out:
  90         return ret;
  91 }
  92
  93 static ssize_t opal_msglog_read(struct file *file, struct kobject *kobj,
  94                                 struct bin_attribute *bin_attr, char *to,
  95                                 loff_t pos, size_t count)
  96 {
  97         return opal_msglog_copy(to, pos, count);
  98 }
  99
 100 static struct bin_attribute opal_msglog_attr = {
 101         .attr = {.name = "msglog", .mode = 0444},
 102         .read = opal_msglog_read
 103 };
 104
 105 void __init opal_msglog_init(void)
 106 {
 107         u64 mcaddr;
 108         struct memcons *mc;
 109
 110         if (of_property_read_u64(opal_node, "ibm,opal-memcons", &mcaddr)) {
 111                 pr_warn("OPAL: Property ibm,opal-memcons not found, no message log\n");
 112                 return;
 113         }
 114
 115         mc = phys_to_virt(mcaddr);
 116         if (!mc) {
 117                 pr_warn("OPAL: memory console address is invalid\n");
 118                 return;
 119         }
 120
 121         if (be64_to_cpu(mc->magic) != MEMCONS_MAGIC) {
 122                 pr_warn("OPAL: memory console version is invalid\n");
 123                 return;
 124         }
 125
 126         opal_memcons = mc;
 127 }
 128
 129 void __init opal_msglog_sysfs_init(void)
 130 {
 131         if (!opal_memcons) {
 132                 pr_warn("OPAL: message log initialisation failed, not creating sysfs entry\n");
 133                 return;
 134         }
 135
 136         if (sysfs_create_bin_file(opal_kobj, &opal_msglog_attr) != 0)
 137                 pr_warn("OPAL: sysfs file creation failed\n");
 138 }