powerpc/powernv: Add OPAL message log interface

OPAL provides an in-memory circular buffer containing a message log
populated with various runtime messages produced by the firmware.

Provide a sysfs interface /sys/firmware/opal/msglog for userspace to
view the messages.

Signed-off-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

4 files changed, 128 insertions, 1 deletions

diff --git a/arch/powerpc/include/asm/opal.h b/arch/powerpc/include/asm/opal.h
index a13ab397edda..05f9455615d6 100644
--- a/arch/powerpc/include/asm/opal.h
+++ b/arch/powerpc/include/asm/opal.h
@@ -730,6 +730,9 @@ typedef struct oppanel_line {
 /* /sys/firmware/opal */
 extern struct kobject *opal_kobj;
 
+/* /ibm,opal */
+extern struct device_node *opal_node;
+
 /* API functions */
 int64_t opal_console_write(int64_t term_number, __be64 *length,
                            const uint8_t *buffer);
@@ -920,6 +923,7 @@ extern void opal_flash_init(void);
 extern int opal_elog_init(void);
 extern void opal_platform_dump_init(void);
 extern void opal_sys_param_init(void);
+extern void opal_msglog_init(void);
 
 extern int opal_machine_check(struct pt_regs *regs);
 extern bool opal_mce_check_early_recovery(struct pt_regs *regs);
diff --git a/arch/powerpc/platforms/powernv/Makefile b/arch/powerpc/platforms/powernv/Makefile
index f324ea099503..63cebb9b4d45 100644
--- a/arch/powerpc/platforms/powernv/Makefile
+++ b/arch/powerpc/platforms/powernv/Makefile
@@ -1,6 +1,7 @@
 obj-y                   += setup.o opal-takeover.o opal-wrappers.o opal.o opal-async.o
 obj-y                   += opal-rtc.o opal-nvram.o opal-lpc.o opal-flash.o
 obj-y                   += rng.o opal-elog.o opal-dump.o opal-sysparam.o opal-sensor.o
+obj-y                   += opal-msglog.o
 
 obj-$(CONFIG_SMP)       += smp.o
 obj-$(CONFIG_PCI)       += pci.o pci-p5ioc2.o pci-ioda.o
diff --git a/arch/powerpc/platforms/powernv/opal-msglog.c b/arch/powerpc/platforms/powernv/opal-msglog.c
new file mode 100644
index 000000000000..1bb25b952504
--- /dev/null
+++ b/arch/powerpc/platforms/powernv/opal-msglog.c
@@ -0,0 +1,120 @@
+/*
+ * PowerNV OPAL in-memory console interface
+ *
+ * Copyright 2014 IBM Corp.
+ *
+ * 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.
+ */
+
+#include <asm/io.h>
+#include <asm/opal.h>
+#include <linux/debugfs.h>
+#include <linux/of.h>
+#include <linux/types.h>
+#include <asm/barrier.h>
+
+/* OPAL in-memory console. Defined in OPAL source at core/console.c */
+struct memcons {
+        __be64 magic;
+#define MEMCONS_MAGIC   0x6630696567726173L
+        __be64 obuf_phys;
+        __be64 ibuf_phys;
+        __be32 obuf_size;
+        __be32 ibuf_size;
+        __be32 out_pos;
+#define MEMCONS_OUT_POS_WRAP    0x80000000u
+#define MEMCONS_OUT_POS_MASK    0x00ffffffu
+        __be32 in_prod;
+        __be32 in_cons;
+};
+
+static ssize_t opal_msglog_read(struct file *file, struct kobject *kobj,
+                                struct bin_attribute *bin_attr, char *to,
+                                loff_t pos, size_t count)
+{
+        struct memcons *mc = bin_attr->private;
+        const char *conbuf;
+        size_t ret, first_read = 0;
+        uint32_t out_pos, avail;
+
+        if (!mc)
+                return -ENODEV;
+
+        out_pos = be32_to_cpu(ACCESS_ONCE(mc->out_pos));
+
+        /* Now we've read out_pos, put a barrier in before reading the new
+         * data it points to in conbuf. */
+        smp_rmb();
+
+        conbuf = phys_to_virt(be64_to_cpu(mc->obuf_phys));
+
+        /* When the buffer has wrapped, read from the out_pos marker to the end
+         * of the buffer, and then read the remaining data as in the un-wrapped
+         * case. */
+        if (out_pos & MEMCONS_OUT_POS_WRAP) {
+
+                out_pos &= MEMCONS_OUT_POS_MASK;
+                avail = be32_to_cpu(mc->obuf_size) - out_pos;
+
+                ret = memory_read_from_buffer(to, count, &pos,
+                                conbuf + out_pos, avail);
+
+                if (ret < 0)
+                        goto out;
+
+                first_read = ret;
+                to += first_read;
+                count -= first_read;
+                pos -= avail;
+        }
+
+        /* Sanity check. The firmware should not do this to us. */
+        if (out_pos > be32_to_cpu(mc->obuf_size)) {
+                pr_err("OPAL: memory console corruption. Aborting read.\n");
+                return -EINVAL;
+        }
+
+        ret = memory_read_from_buffer(to, count, &pos, conbuf, out_pos);
+
+        if (ret < 0)
+                goto out;
+
+        ret += first_read;
+out:
+        return ret;
+}
+
+static struct bin_attribute opal_msglog_attr = {
+        .attr = {.name = "msglog", .mode = 0444},
+        .read = opal_msglog_read
+};
+
+void __init opal_msglog_init(void)
+{
+        u64 mcaddr;
+        struct memcons *mc;
+
+        if (of_property_read_u64(opal_node, "ibm,opal-memcons", &mcaddr)) {
+                pr_warn("OPAL: Property ibm,opal-memcons not found, no message log\n");
+                return;
+        }
+
+        mc = phys_to_virt(mcaddr);
+        if (!mc) {
+                pr_warn("OPAL: memory console address is invalid\n");
+                return;
+        }
+
+        if (be64_to_cpu(mc->magic) != MEMCONS_MAGIC) {
+                pr_warn("OPAL: memory console version is invalid\n");
+                return;
+        }
+
+        opal_msglog_attr.private = mc;
+
+        if (sysfs_create_bin_file(opal_kobj, &opal_msglog_attr) != 0)
+                pr_warn("OPAL: sysfs file creation failed\n");
+}
diff --git a/arch/powerpc/platforms/powernv/opal.c b/arch/powerpc/platforms/powernv/opal.c
index 3697772e3759..99e9c2887e21 100644
--- a/arch/powerpc/platforms/powernv/opal.c
+++ b/arch/powerpc/platforms/powernv/opal.c
@@ -46,7 +46,7 @@ struct mcheck_recoverable_range {
 static struct mcheck_recoverable_range *mc_recoverable_range;
 static int mc_recoverable_range_len;
 
-static struct device_node *opal_node;
+struct device_node *opal_node;
 static DEFINE_SPINLOCK(opal_write_lock);
 extern u64 opal_mc_secondary_handler[];
 static unsigned int *opal_irqs;
@@ -602,6 +602,8 @@ static int __init opal_init(void)
                 opal_platform_dump_init();
                 /* Setup system parameters interface */
                 opal_sys_param_init();
+                /* Setup message log interface. */
+                opal_msglog_init();
         }
 
         return 0;