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/messages 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, 106 insertions, 2 deletions

diff --git a/arch/powerpc/include/asm/opal.h b/arch/powerpc/include/asm/opal.h
index 5c34170a293ce..1d6883a2ac11c 100644
--- a/arch/powerpc/include/asm/opal.h
+++ b/arch/powerpc/include/asm/opal.h
@@ -736,6 +736,9 @@ 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, int64_t *length,
 			   const uint8_t *buffer);
@@ -926,6 +929,7 @@ extern void opal_flash_term_callback(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 b51ce5910b7a0..f5d4149d427c7 100644
--- a/arch/powerpc/platforms/powernv/Makefile
+++ b/arch/powerpc/platforms/powernv/Makefile
@@ -1,6 +1,6 @@
 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 opal-sysparam.o
-obj-y			+= rng.o opal-dump.o opal-elog.o opal-sensor.o
+obj-y			+= rng.o opal-dump.o opal-elog.o opal-sensor.o opal-msglog.o
 obj-y			+= subcore.o subcore-asm.o
 
 obj-$(CONFIG_SMP)	+= smp.o
diff --git a/arch/powerpc/platforms/powernv/opal-msglog.c b/arch/powerpc/platforms/powernv/opal-msglog.c
new file mode 100644
index 0000000000000..5cb562d033d4a
--- /dev/null
+++ b/arch/powerpc/platforms/powernv/opal-msglog.c
@@ -0,0 +1,98 @@
+/*
+ * 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>
+
+/* 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;
+	bool wrapped;
+	size_t num_read;
+	int out_pos;
+
+	if (!mc)
+		return -ENODEV;
+
+	conbuf = phys_to_virt(be64_to_cpu(mc->obuf_phys));
+	wrapped = be32_to_cpu(mc->out_pos) & MEMCONS_OUT_POS_WRAP;
+	out_pos = be32_to_cpu(mc->out_pos) & MEMCONS_OUT_POS_MASK;
+
+	if (!wrapped) {
+		num_read = memory_read_from_buffer(to, count, &pos, conbuf,
+				out_pos);
+	} else {
+		num_read = memory_read_from_buffer(to, count, &pos,
+				conbuf + out_pos,
+				be32_to_cpu(mc->obuf_size) - out_pos);
+
+		if (num_read < 0)
+			goto out;
+
+		num_read += memory_read_from_buffer(to + num_read,
+				count - num_read, &pos, conbuf, out_pos);
+	}
+out:
+	return num_read;
+}
+
+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 ea8e717317ff1..659adc8090475 100644
--- a/arch/powerpc/platforms/powernv/opal.c
+++ b/arch/powerpc/platforms/powernv/opal.c
@@ -62,7 +62,7 @@ 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;
@@ -668,6 +668,8 @@ 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();
 	}
 
 	/* Add debugfs access to OPAL log */