With OPALv3, the firmware can provide the address of it's internal console
to Linux, which we can then display using debugfs. This is handy for
diagnostics and debugging.
Signed-off-by: Benjamin Herrenschmidt <b...@kernel.crashing.org>
---
diff --git a/arch/powerpc/platforms/powernv/opal.c
b/arch/powerpc/platforms/powernv/opal.c
index 2911abe..10d7894 100644
--- a/arch/powerpc/platforms/powernv/opal.c
+++ b/arch/powerpc/platforms/powernv/opal.c
@@ -17,6 +17,8 @@
#include <linux/interrupt.h>
#include <linux/notifier.h>
#include <linux/slab.h>
+#include <linux/debugfs.h>
+#include <linux/uaccess.h>
#include <asm/opal.h>
#include <asm/firmware.h>
@@ -27,6 +29,21 @@ struct opal {
u64 entry;
} opal;
+/* OPAL in-memory console */
+struct memcons {
+ uint64_t magic;
+#define MEMCONS_MAGIC 0x6630696567726173
+ uint64_t obuf_phys;
+ uint64_t ibuf_phys;
+ uint32_t obuf_size;
+ uint32_t ibuf_size;
+ uint32_t out_pos;
+#define MEMCONS_OUT_POS_WRAP 0x80000000u
+#define MEMCONS_OUT_POS_MASK 0x00ffffffu
+ uint32_t in_prod;
+ uint32_t in_cons;
+};
+
static struct device_node *opal_node;
static DEFINE_SPINLOCK(opal_write_lock);
extern u64 opal_mc_secondary_handler[];
@@ -369,6 +386,90 @@ static irqreturn_t opal_interrupt(int irq, void *data)
return IRQ_HANDLED;
}
+#ifdef CONFIG_DEBUG_FS
+static ssize_t opal_memcons_read(struct file *file, char __user *to,
+ size_t count, loff_t *ppos)
+{
+ struct memcons *mc = file->private_data;
+ size_t available, ret, chunk0, chunk1, lcount;
+ const char *start, *conbuf = __va(mc->obuf_phys);
+ loff_t opos, pos;
+
+ /*
+ * Find out how much is in the buffer. If it has wrapped
+ * the whole buffer, else just the beginning. It has wrapped
+ * if the next character is not \0
+ */
+ if (mc->out_pos & MEMCONS_OUT_POS_WRAP) {
+ available = mc->obuf_size;
+ chunk1 = mc->out_pos & MEMCONS_OUT_POS_MASK;
+ start = conbuf + chunk1;
+ chunk0 = mc->obuf_size - chunk1;
+ } else {
+ available = mc->out_pos;
+ start = conbuf;
+ chunk0 = available;
+ chunk1 = 0;
+ }
+
+ opos = pos = *ppos;
+
+ /* Sanity check arguments */
+ if (pos < 0)
+ return -EINVAL;
+ if (pos >= available || !count)
+ return 0;
+ if (count > available - pos)
+ count = available - pos;
+
+ /* Handle first chunk */
+ if (pos < chunk0) {
+ lcount = min(count, chunk0 - (size_t)pos);
+ ret = copy_to_user(to, start + pos, lcount);
+ if (ret == lcount)
+ return -EFAULT;
+ lcount -= ret;
+ count -= lcount;
+ *ppos += lcount;
+ to += lcount;
+ pos = 0;
+ } else {
+ *ppos += chunk0;
+ pos -= chunk0;
+ ret = 0;
+ }
+
+ /* Handle second chunk */
+ if (count && chunk1 && ret == 0) {
+ lcount = min(count, chunk1 - (size_t)pos);
+ ret = copy_to_user(to, conbuf + pos, lcount);
+ if (ret == lcount)
+ return -EFAULT;
+ lcount -= ret;
+ *ppos += lcount;
+ }
+ return *ppos - opos;
+
+}
+
+static const struct file_operations opal_fops_memcons = {
+ .read = opal_memcons_read,
+ .open = simple_open,
+ .llseek = default_llseek,
+};
+
+static void opal_init_debugfs(void)
+{
+ u64 mcaddr;
+
+ if (of_property_read_u64(opal_node, "ibm,opal-memcons", &mcaddr) == 0)
+ debugfs_create_file("opal-log", 0400, powerpc_debugfs_root,
+ __va(mcaddr), &opal_fops_memcons);
+}
+#else
+static void opal_init_debugfs(void) { }
+#endif /* CONFIG_DEBUG_FS */
+
static int __init opal_init(void)
{
struct device_node *np, *consoles;
@@ -414,6 +515,9 @@ static int __init opal_init(void)
" (0x%x)\n", rc, irq, hwirq);
opal_irqs[i] = irq;
}
+
+ opal_init_debugfs();
+
return 0;
}
subsys_initcall(opal_init);
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