[PATCH] collie: don't read GPSR

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 <redacted>
---
 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

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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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
[off-list ref] wrote:

On 6/17/11, Eric Miao [off-list ref] 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
[off-list ref] wrote:

quoted

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 <redacted>
---
 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