Patchwork powerpc/powernv: Add a debugfs file to read the firmware console

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Submitter Benjamin Herrenschmidt
Date Oct. 8, 2013, 7:46 a.m.
Message ID <1381218400.645.204.camel@pasglop>
Download mbox | patch
Permalink /patch/281346/
State Superseded
Headers show

Comments

Benjamin Herrenschmidt - Oct. 8, 2013, 7:46 a.m.
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 <benh@kernel.crashing.org>
---
Michael Ellerman - Oct. 9, 2013, 3:23 a.m.
On Tue, Oct 08, 2013 at 06:46:40PM +1100, Benjamin Herrenschmidt wrote:
> 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 <benh@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 */

It might be nice to point out that the format of the struct is defined
by OPAL and must be in sync with what OPAL is using.

> +struct memcons {
> +	uint64_t magic;

u64 ?

> +#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

Where does this come from?

> +	uint32_t in_prod;
> +	uint32_t in_cons;
> +};

Should it be packed?

> @@ -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;
> +	}

Surely simple_read_from_buffer() could make some of this simpler?


cheers
Benjamin Herrenschmidt - Oct. 9, 2013, 4:23 a.m.
On Wed, 2013-10-09 at 14:23 +1100, Michael Ellerman wrote:
> On Tue, Oct 08, 2013 at 06:46:40PM +1100, Benjamin Herrenschmidt wrote:
> > 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 <benh@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 */
> 
> It might be nice to point out that the format of the struct is defined
> by OPAL and must be in sync with what OPAL is using.

Yes, we could move the structure definition to opal.h...

> > +struct memcons {
> > +	uint64_t magic;
> 
> u64 ?

Who cares ? Especially if it goes into opal.h it should stick to the
types used in that file.

> > +#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
> 
> Where does this come from?

My a** :-) I made it up as I wrote the OPAL side one, why ?

> > +	uint32_t in_prod;
> > +	uint32_t in_cons;
> > +};
> 
> Should it be packed?

Nope, no need. It's all nice and naturally aligned.

> > @@ -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;
> > +	}
> 
> Surely simple_read_from_buffer() could make some of this simpler?

If you can find a way to make it deal with a ring buffer...

Cheers,
Ben.
Michael Ellerman - Oct. 9, 2013, 6:06 a.m.
On Wed, Oct 09, 2013 at 03:23:21PM +1100, Benjamin Herrenschmidt wrote:
> On Wed, 2013-10-09 at 14:23 +1100, Michael Ellerman wrote:
> > On Tue, Oct 08, 2013 at 06:46:40PM +1100, Benjamin Herrenschmidt wrote:
> > > 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 <benh@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 */
> > 
> > It might be nice to point out that the format of the struct is defined
> > by OPAL and must be in sync with what OPAL is using.
> 
> Yes, we could move the structure definition to opal.h...
> 
> > > +struct memcons {
> > > +	uint64_t magic;
> > 
> > u64 ?
> 
> Who cares ? 

That's what we use in the kernel. But no I don't care.

> > > +#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
> > 
> > Where does this come from?
> 
> My a** :-) I made it up as I wrote the OPAL side one, why ?

...
 
> > > +	uint32_t in_prod;
> > > +	uint32_t in_cons;
> > > +};
> > 
> > Should it be packed?
> 
> Nope, no need. It's all nice and naturally aligned.

Sure, that's obvious.
 
> > > @@ -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;
> > > +	}
> > 
> > Surely simple_read_from_buffer() could make some of this simpler?
> 
> If you can find a way to make it deal with a ring buffer...

Call it twice.

And you wonder why no one reviews your patches?

cheers
Benjamin Herrenschmidt - Oct. 9, 2013, 6:51 a.m.
On Wed, 2013-10-09 at 17:06 +1100, Michael Ellerman wrote:
> Call it twice.
> 
> And you wonder why no one reviews your patches?

Not that easy :-) I had a look at using it and unless I did something
stupid, it wasn't actually that trivial to figure out what arg to pass
it for calling it twice, ie, it didn't simplify the code
significantly ... I had another problem too but I don't remember what
it was. But it could be that I had a very dumb moment...

Cheers,
Ben.

Patch

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);