Patchwork [U-Boot,4/9] Exynos: Avoid a divide by zero by specifying a non-zero period for pwm 4

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Submitter Akshay Saraswat
Date Feb. 27, 2013, 10:02 a.m.
Message ID <1361959366-27634-5-git-send-email-akshay.s@samsung.com>
Download mbox | patch
Permalink /patch/223568/
State Changes Requested
Delegated to: Minkyu Kang
Headers show

Comments

Akshay Saraswat - Feb. 27, 2013, 10:02 a.m.
The pwm_config function in the exynos pwm driver divides by its period
period parameter. A function was calling pwm_config with a 0ns period and a
0ns duty cycle. That doesn't actually make any sense physically, and results
in a divide by zero in the driver. This change changes the paremters to be a
100000ns period and duty cycle.

TEST=sf probe 1:0; time sf read 40008000 0 1000
Try with different numbers of bytes and see that sane values are obtained
Build and boot U-boot with this patch, backlight works properly.

Signed-off-by: Gabe Black <gabeblack@google.com>
Signed-off-by: Akshay Saraswat <akshay.s@samsung.com>
---
 arch/arm/cpu/armv7/s5p-common/timer.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
Simon Glass - Feb. 28, 2013, 1:29 a.m.
On Wed, Feb 27, 2013 at 2:02 AM, Akshay Saraswat <akshay.s@samsung.com> wrote:
> The pwm_config function in the exynos pwm driver divides by its period
> period parameter. A function was calling pwm_config with a 0ns period and a
> 0ns duty cycle. That doesn't actually make any sense physically, and results
> in a divide by zero in the driver. This change changes the paremters to be a
> 100000ns period and duty cycle.
>
> TEST=sf probe 1:0; time sf read 40008000 0 1000
> Try with different numbers of bytes and see that sane values are obtained
> Build and boot U-boot with this patch, backlight works properly.
>
> Signed-off-by: Gabe Black <gabeblack@google.com>
> Signed-off-by: Akshay Saraswat <akshay.s@samsung.com>

Acked-by: Simon Glass <sjg@chromium.org>

> ---
>  arch/arm/cpu/armv7/s5p-common/timer.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/arm/cpu/armv7/s5p-common/timer.c b/arch/arm/cpu/armv7/s5p-common/timer.c
> index de61405..6a0fa58 100644
> --- a/arch/arm/cpu/armv7/s5p-common/timer.c
> +++ b/arch/arm/cpu/armv7/s5p-common/timer.c
> @@ -58,7 +58,7 @@ int timer_init(void)
>  {
>         /* PWM Timer 4 */
>         pwm_init(4, MUX_DIV_4, 0);
> -       pwm_config(4, 0, 0);
> +       pwm_config(4, 100000, 100000);
>         pwm_enable(4);
>
>         /* Use this as the current monotonic time in us */
> --
> 1.8.0
>

Patch

diff --git a/arch/arm/cpu/armv7/s5p-common/timer.c b/arch/arm/cpu/armv7/s5p-common/timer.c
index de61405..6a0fa58 100644
--- a/arch/arm/cpu/armv7/s5p-common/timer.c
+++ b/arch/arm/cpu/armv7/s5p-common/timer.c
@@ -58,7 +58,7 @@  int timer_init(void)
 {
 	/* PWM Timer 4 */
 	pwm_init(4, MUX_DIV_4, 0);
-	pwm_config(4, 0, 0);
+	pwm_config(4, 100000, 100000);
 	pwm_enable(4);
 
 	/* Use this as the current monotonic time in us */