linux-kernel - Re: [PATCH] microblaze: improve failure handling for GPIO reset

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Message-ID: <4FE2C082.1060302@monstr.eu>
Date:	Thu, 21 Jun 2012 08:34:42 +0200
From:	Michal Simek <monstr@...str.eu>
To:	Stephan Linz <linz@...pro.net>
CC:	microblaze-uclinux@...e.uq.edu.au, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] microblaze: improve failure handling for GPIO reset

On 06/20/2012 10:36 PM, Stephan Linz wrote:
> Early exit from of_platform_reset_gpio_probe() if there
> was no GPIO reset line configured.
>
> Avoid kernel oops in gpio_system_reset():
>
> [   27.413294] Restarting system.
> [   27.415674] Machine restart...
> [   27.418787] Oops: kernel access of bad area, sig: 11
> [   27.423252]  Registers dump: mode=83871D1C
> [   27.427428]  r1=00000000, r2=00000000, r3=FFFFFEF8, r4=00000000
> [   27.433310]  r5=C026AED0, r6=00000001, r7=00000068, r8=00000000
> [   27.439189]  r9=C3871DAC, r10=000011A5, r11=00000000, r12=0000000A
> [   27.445318]  r13=00000000, r14=0000000F, r15=C00029BC, r16=00000000
> [   27.451558]  r17=C011DE8C, r18=80000115, r19=0000000F, r20=48184ED8
> [   27.457770]  r21=00000000, r22=FFFFFFEA, r23=00000001, r24=FEE1DEAD
> [   27.463982]  r25=00000054, r26=1000B1C8, r27=00000000, r28=00000000
> [   27.470208]  r29=00000000, r30=00000000, r31=C32D30C0, rPC=C011DE8C
> [   27.476433]  msr=000042A2, ear=0000004B, esr=00000872, fsr=342E3732
>
> Signed-off-by: Stephan Linz<linz@...pro.net>
> ---
>   arch/microblaze/kernel/reset.c |    5 ++++-
>   1 files changed, 4 insertions(+), 1 deletions(-)
>
> diff --git a/arch/microblaze/kernel/reset.c b/arch/microblaze/kernel/reset.c
> index 88a0163..7a08071 100644
> --- a/arch/microblaze/kernel/reset.c
> +++ b/arch/microblaze/kernel/reset.c
> @@ -28,6 +28,7 @@ void of_platform_reset_gpio_probe(void)
>   	if (!gpio_is_valid(handle)) {
>   		printk(KERN_INFO "Skipping unavailable RESET gpio %d (%s)\n",
>   				handle, "reset");
> +		return;
>   	}
>
>   	ret = gpio_request(handle, "reset");
> @@ -60,7 +61,8 @@ err:
>
>   static void gpio_system_reset(void)
>   {
> -	gpio_set_value(handle, 1 - reset_val);
> +	if (gpio_is_valid(handle))
> +		gpio_set_value(handle, 1 - reset_val);
>   }
>   #else
>   #define gpio_system_reset() do {} while (0)
> @@ -74,6 +76,7 @@ void machine_restart(char *cmd)
>   {
>   	printk(KERN_NOTICE "Machine restart...\n");
>   	gpio_system_reset();
> +	printk(KERN_NOTICE "Dump stack on machines without reset line ...\n");
>   	dump_stack();
>   	while (1)
>   		;

Your changes looks good. Some weeks ago we have changed this code a little bit too by removing dump_stack()
and change printk message to "NO reset GPIO available in the system" or similar.
I think we can add these two changes together because truth is that dump_stack didn't give you any useful
output.

Thanks,
Michal



-- 
Michal Simek, Ing. (M.Eng)
w: www.monstr.eu p: +42-0-721842854
Maintainer of Linux kernel 2.6 Microblaze Linux - http://www.monstr.eu/fdt/
Microblaze U-BOOT custodian
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