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 ssize_t opal_msglog_read(struct file *file, struct kobject *kobj,
  35                                 struct bin_attribute *bin_attr, char *to,
  36                                 loff_t pos, size_t count)
  37 {
  38         struct memcons *mc = bin_attr->private;
  39         const char *conbuf;
  40         ssize_t ret;
  41         size_t first_read = 0;
  42         uint32_t out_pos, avail;
  43
  44         if (!mc)
  45                 return -ENODEV;
  46
  47         out_pos = be32_to_cpu(ACCESS_ONCE(mc->out_pos));
  48
  49         /* Now we've read out_pos, put a barrier in before reading the new
  50          * data it points to in conbuf. */
  51         smp_rmb();
  52
  53         conbuf = phys_to_virt(be64_to_cpu(mc->obuf_phys));
  54
  55         /* When the buffer has wrapped, read from the out_pos marker to the end
  56          * of the buffer, and then read the remaining data as in the un-wrapped
  57          * case. */
  58         if (out_pos & MEMCONS_OUT_POS_WRAP) {
  59
  60                 out_pos &= MEMCONS_OUT_POS_MASK;
  61                 avail = be32_to_cpu(mc->obuf_size) - out_pos;
  62
  63                 ret = memory_read_from_buffer(to, count, &pos,
  64                                 conbuf + out_pos, avail);
  65
  66                 if (ret < 0)
  67                         goto out;
  68
  69                 first_read = ret;
  70                 to += first_read;
  71                 count -= first_read;
  72                 pos -= avail;
  73
  74                 if (count <= 0)
  75                         goto out;
  76         }
  77
  78         /* Sanity check. The firmware should not do this to us. */
  79         if (out_pos > be32_to_cpu(mc->obuf_size)) {
  80                 pr_err("OPAL: memory console corruption. Aborting read.\n");
  81                 return -EINVAL;
  82         }
  83
  84         ret = memory_read_from_buffer(to, count, &pos, conbuf, out_pos);
  85
  86         if (ret < 0)
  87                 goto out;
  88
  89         ret += first_read;
  90 out:
  91         return ret;
  92 }
  93
  94 static struct bin_attribute opal_msglog_attr = {
  95         .attr = {.name = "msglog", .mode = 0444},
  96         .read = opal_msglog_read
  97 };
  98
  99 void __init opal_msglog_init(void)
 100 {
 101         u64 mcaddr;
 102         struct memcons *mc;
 103
 104         if (of_property_read_u64(opal_node, "ibm,opal-memcons", &mcaddr)) {
 105                 pr_warn("OPAL: Property ibm,opal-memcons not found, no message log\n");
 106                 return;
 107         }
 108
 109         mc = phys_to_virt(mcaddr);
 110         if (!mc) {
 111                 pr_warn("OPAL: memory console address is invalid\n");
 112                 return;
 113         }
 114
 115         if (be64_to_cpu(mc->magic) != MEMCONS_MAGIC) {
 116                 pr_warn("OPAL: memory console version is invalid\n");
 117                 return;
 118         }
 119
 120         opal_msglog_attr.private = mc;
 121
 122         if (sysfs_create_bin_file(opal_kobj, &opal_msglog_attr) != 0)
 123                 pr_warn("OPAL: sysfs file creation failed\n");
 124 }