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 } 125