[PATCH] powerpc/4xx: Add optional "reset_type" property to control reboot via dts

[PATCH] powerpc/4xx: Add optional "reset_type" property to control reboot via dts

[Stefan Roese]

By setting "reset_type" to one of the following values, the default
software reset mechanism may be overidden. Here the possible values of
"reset_type":

  1 - PPC4xx core reset
  2 - PPC4xx chip reset
  3 - PPC4xx system reset (default)

This will be used by a new PPC440SPe board port, which needs a "chip
reset" instead of the default "system reset" to be asserted.

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Josh Boyer <jwboyer@linux.vnet.ibm.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
---
 arch/powerpc/sysdev/ppc4xx_soc.c |   17 +++++++++++++++--
 1 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/sysdev/ppc4xx_soc.c b/arch/powerpc/sysdev/ppc4xx_soc.c
index 5c01435..fe54216 100644
--- a/arch/powerpc/sysdev/ppc4xx_soc.c
+++ b/arch/powerpc/sysdev/ppc4xx_soc.c
@@ -191,11 +191,24 @@ static int __init ppc4xx_l2c_probe(void)
 arch_initcall(ppc4xx_l2c_probe);
 
 /*
- * At present, this routine just applies a system reset.
+ * Apply a system reset. Alternatively a board specific value may be
+ * provided via the "reset-type" property in the cpu node.
  */
 void ppc4xx_reset_system(char *cmd)
 {
-	mtspr(SPRN_DBCR0, mfspr(SPRN_DBCR0) | DBCR0_RST_SYSTEM);
+	struct device_node *np;
+	u32 reset_type = DBCR0_RST_SYSTEM;
+	const u32 *prop;
+
+	np = of_find_node_by_type(NULL, "cpu");
+	if (np) {
+		prop = of_get_property(np, "reset-type", NULL);
+		if (prop)
+			reset_type = prop[0] << 28;
+	}
+
+	mtspr(SPRN_DBCR0, mfspr(SPRN_DBCR0) | reset_type);
+
 	while (1)
 		;	/* Just in case the reset doesn't work */
 }
-- 
1.7.1

Re: [PATCH] powerpc/4xx: Add optional "reset_type" property to control reboot via dts

[Josh Boyer]

On Mon, Apr 26, 2010 at 03:39:01PM +0200, Stefan Roese wrote:
>By setting "reset_type" to one of the following values, the default
>software reset mechanism may be overidden. Here the possible values of
>"reset_type":

NEAT!  A 4xx patch!  I haven't gotten enough of these lately, so forgive my
nit picking ;)

>
>  1 - PPC4xx core reset
>  2 - PPC4xx chip reset
>  3 - PPC4xx system reset (default)

We should probably put a brief description of this in the dts bindings under
Documentation (or whereever we're storing them these days.  I saw something
about a wiki?).

Also, while it's not a large issue, I wonder if there will be confusion on
whether 'reset-type' is "the type of reset to use" or "the type of reset that
was just done".  There are some products that actually care about the latter for
various RAS issues.  I don't, however, have a great alternative property name
that comes to mind though.

>This will be used by a new PPC440SPe board port, which needs a "chip
>reset" instead of the default "system reset" to be asserted.

I'm curious why that is?

>Signed-off-by: Stefan Roese <sr@denx.de>
>Cc: Josh Boyer <jwboyer@linux.vnet.ibm.com>
>Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
>---
> arch/powerpc/sysdev/ppc4xx_soc.c |   17 +++++++++++++++--
> 1 files changed, 15 insertions(+), 2 deletions(-)
>
>diff --git a/arch/powerpc/sysdev/ppc4xx_soc.c b/arch/powerpc/sysdev/ppc4xx_soc.c
>index 5c01435..fe54216 100644
>--- a/arch/powerpc/sysdev/ppc4xx_soc.c
>+++ b/arch/powerpc/sysdev/ppc4xx_soc.c
>@@ -191,11 +191,24 @@ static int __init ppc4xx_l2c_probe(void)
> arch_initcall(ppc4xx_l2c_probe);
>
> /*
>- * At present, this routine just applies a system reset.
>+ * Apply a system reset. Alternatively a board specific value may be
>+ * provided via the "reset-type" property in the cpu node.
>  */
> void ppc4xx_reset_system(char *cmd)
> {
>-	mtspr(SPRN_DBCR0, mfspr(SPRN_DBCR0) | DBCR0_RST_SYSTEM);
>+	struct device_node *np;
>+	u32 reset_type = DBCR0_RST_SYSTEM;
>+	const u32 *prop;
>+
>+	np = of_find_node_by_type(NULL, "cpu");
>+	if (np) {
>+		prop = of_get_property(np, "reset-type", NULL);
>+		if (prop)
>+			reset_type = prop[0] << 28;
>+	}

While I don't think it's a big issue, I wonder if we should sanity check the
resulting value here.  I could see someone being dumb and doing:

	reset-type = "system";

or something like that.  If that is done, what would the resulting shift on it
turn into?

josh

Re: [PATCH] powerpc/4xx: Add optional "reset_type" property to control reboot via dts

[Stefan Roese]

Hi Josh,

On Monday 26 April 2010 20:28:29 Josh Boyer wrote:
> On Mon, Apr 26, 2010 at 03:39:01PM +0200, Stefan Roese wrote:
> >By setting "reset_type" to one of the following values, the default
> >software reset mechanism may be overidden. Here the possible values of
> 
> >"reset_type":
> NEAT!  A 4xx patch!  I haven't gotten enough of these lately, so forgive my
> nit picking ;)

Sure. Comments welcome, as always.
 
> >  1 - PPC4xx core reset
> >  2 - PPC4xx chip reset
> >  3 - PPC4xx system reset (default)
> 
> We should probably put a brief description of this in the dts bindings
> under Documentation (or whereever we're storing them these days.  I saw
> something about a wiki?).

Right. I thought about this as well (too late). I'll include a short 
documentation in my next patch version.
 
> Also, while it's not a large issue, I wonder if there will be confusion on
> whether 'reset-type' is "the type of reset to use" or "the type of reset
> that was just done".  There are some products that actually care about the
> latter for various RAS issues.  I don't, however, have a great alternative
> property name that comes to mind though.

I'll stick with this name for now then.
 
> >This will be used by a new PPC440SPe board port, which needs a "chip
> >reset" instead of the default "system reset" to be asserted.
> 
> I'm curious why that is?

Hmmm. Frankly, I can't remember the background here. You might what to check 
this for yourself. Katmai has the same issue. And I just copied this reboot 
code from Katmai for this new 440SPe board.

BTW: Once this patch is finished/accepted, I'll cook up a short katmai patch 
to fix this reboot issue here too.
 
> >Signed-off-by: Stefan Roese <sr@denx.de>
> >Cc: Josh Boyer <jwboyer@linux.vnet.ibm.com>
> >Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> >---
> >
> > arch/powerpc/sysdev/ppc4xx_soc.c |   17 +++++++++++++++--
> > 1 files changed, 15 insertions(+), 2 deletions(-)
> >
> >diff --git a/arch/powerpc/sysdev/ppc4xx_soc.c
> >b/arch/powerpc/sysdev/ppc4xx_soc.c index 5c01435..fe54216 100644
> >--- a/arch/powerpc/sysdev/ppc4xx_soc.c
> >+++ b/arch/powerpc/sysdev/ppc4xx_soc.c
> >@@ -191,11 +191,24 @@ static int __init ppc4xx_l2c_probe(void)
> >
> > arch_initcall(ppc4xx_l2c_probe);
> > 
> > /*
> >
> >- * At present, this routine just applies a system reset.
> >+ * Apply a system reset. Alternatively a board specific value may be
> >+ * provided via the "reset-type" property in the cpu node.
> >
> >  */
> > 
> > void ppc4xx_reset_system(char *cmd)
> > {
> >
> >-	mtspr(SPRN_DBCR0, mfspr(SPRN_DBCR0) | DBCR0_RST_SYSTEM);
> >+	struct device_node *np;
> >+	u32 reset_type = DBCR0_RST_SYSTEM;
> >+	const u32 *prop;
> >+
> >+	np = of_find_node_by_type(NULL, "cpu");
> >+	if (np) {
> >+		prop = of_get_property(np, "reset-type", NULL);
> >+		if (prop)
> >+			reset_type = prop[0] << 28;
> >+	}
> 
> While I don't think it's a big issue, I wonder if we should sanity check
> the resulting value here.  I could see someone being dumb and doing:
> 
> 	reset-type = "system";
> 
> or something like that.  If that is done, what would the resulting shift on
> it turn into?

Good idea. I'll add a check in the next version.

Thanks.

Cheers,
Stefan