[PATCH] collie: don't read GPSR

[PATCH] collie: don't read GPSR

[Dmitry Eremin-Solenikov]

On StrongARM GPSR is write-only according to docs, so don't read from
it. Just set the required GPIO.

Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
---
 arch/arm/mach-sa1100/collie.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/arch/arm/mach-sa1100/collie.c b/arch/arm/mach-sa1100/collie.c
index f28025e..3f32ba2 100644
--- a/arch/arm/mach-sa1100/collie.c
+++ b/arch/arm/mach-sa1100/collie.c
@@ -339,7 +339,7 @@ static void __init collie_init(void)
 
 	PCFR = PCFR_OPDE;
 
-	GPSR |= _COLLIE_GPIO_UCB1x00_RESET;
+	GPSR = _COLLIE_GPIO_UCB1x00_RESET;
 
 
 	platform_scoop_config = &collie_pcmcia_config;
-- 
1.7.5.3

[PATCH] collie: don't read GPSR

[Lothar Waßmann]

Hi,

Dmitry Eremin-Solenikov writes:
> On StrongARM GPSR is write-only according to docs, so don't read from
> it. Just set the required GPIO.
> 
Anyway GPSR (and GPCR) is a bit oriented register that allows
asserting individual bits without the need for read-modify-write
cycles, making the access inherently multithread safe. Using
read-modify-write on this register is contrary to the HW design.

A quick grep of the kernel source shows another abuse like this in
drivers/video/sa1100fb.c:             GPSR |= SHANNON_GPIO_DISP_EN;
drivers/video/sa1100fb.c:             GPCR |= SHANNON_GPIO_DISP_EN;


Lothar Wa?mann
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[PATCH] collie: don't read GPSR

[Eric Miao]

Would it be better to switch to use gpio_* API instead of manipulating
GPxR directly?

On Fri, Jun 17, 2011 at 10:11 PM, Dmitry Eremin-Solenikov
<dbaryshkov@gmail.com> wrote:
> On StrongARM GPSR is write-only according to docs, so don't read from
> it. Just set the required GPIO.
>
> Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
> ---
> ?arch/arm/mach-sa1100/collie.c | ? ?2 +-
> ?1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/arch/arm/mach-sa1100/collie.c b/arch/arm/mach-sa1100/collie.c
> index f28025e..3f32ba2 100644
> --- a/arch/arm/mach-sa1100/collie.c
> +++ b/arch/arm/mach-sa1100/collie.c
> @@ -339,7 +339,7 @@ static void __init collie_init(void)
>
> ? ? ? ?PCFR = PCFR_OPDE;
>
> - ? ? ? GPSR |= _COLLIE_GPIO_UCB1x00_RESET;
> + ? ? ? GPSR = _COLLIE_GPIO_UCB1x00_RESET;
>
>
> ? ? ? ?platform_scoop_config = &collie_pcmcia_config;
> --
> 1.7.5.3
>
>

[PATCH] collie: don't read GPSR

[Dmitry Eremin-Solenikov]

On 6/17/11, Eric Miao <eric.y.miao@gmail.com> wrote:
> Would it be better to switch to use gpio_* API instead of manipulating
> GPxR directly?

Yes. Probably. But this would require a much bigger cleanup effort. Waiting
for spare time for it.

> On Fri, Jun 17, 2011 at 10:11 PM, Dmitry Eremin-Solenikov
> <dbaryshkov@gmail.com> wrote:
>> On StrongARM GPSR is write-only according to docs, so don't read from
>> it. Just set the required GPIO.
>>
>> Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
>> ---
>>  arch/arm/mach-sa1100/collie.c |    2 +-
>>  1 files changed, 1 insertions(+), 1 deletions(-)
>>
>> diff --git a/arch/arm/mach-sa1100/collie.c b/arch/arm/mach-sa1100/collie.c
>> index f28025e..3f32ba2 100644
>> --- a/arch/arm/mach-sa1100/collie.c
>> +++ b/arch/arm/mach-sa1100/collie.c
>> @@ -339,7 +339,7 @@ static void __init collie_init(void)
>>
>>        PCFR = PCFR_OPDE;
>>
>> -       GPSR |= _COLLIE_GPIO_UCB1x00_RESET;
>> +       GPSR = _COLLIE_GPIO_UCB1x00_RESET;
>>
>>
>>        platform_scoop_config = &collie_pcmcia_config;
>> --
>> 1.7.5.3
>>
>>
>


-- 
With best wishes
Dmitry