diff mbox

[3/4] pwm: omap-dmtimer: round load and match values rather than truncate

Message ID 1454128014-22866-4-git-send-email-drivshin.allworx@gmail.com (mailing list archive)
State New, archived
Headers show

Commit Message

David Rivshin (Allworx) Jan. 30, 2016, 4:26 a.m. UTC 
From: David Rivshin <drivshin@allworx.com>

When converting period and duty_cycle from nanoseconds to fclk cycles,
the error introduced by the integer division can be appreciable, especially
in the case of slow fclk or short period. Use DIV_ROUND_CLOSEST_ULL() so
that the error is kept to +/- 0.5 clock cycles.

Fixes: 6604c6556db9 ("pwm: Add PWM driver for OMAP using dual-mode timers")
Signed-off-by: David Rivshin <drivshin@allworx.com>
---
 drivers/pwm/pwm-omap-dmtimer.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

Comments

Neil Armstrong Feb. 3, 2016, 10:24 a.m. UTC | #1 
On 01/30/2016 05:26 AM, David Rivshin (Allworx) wrote:
> From: David Rivshin <drivshin@allworx.com>
> 
> When converting period and duty_cycle from nanoseconds to fclk cycles,
> the error introduced by the integer division can be appreciable, especially
> in the case of slow fclk or short period. Use DIV_ROUND_CLOSEST_ULL() so
> that the error is kept to +/- 0.5 clock cycles.
> 
> Fixes: 6604c6556db9 ("pwm: Add PWM driver for OMAP using dual-mode timers")
> Signed-off-by: David Rivshin <drivshin@allworx.com>

OK for me.

Acked-by: Neil Armstrong <narmstrong@baylibre.com>

Thanks !

> ---
>  drivers/pwm/pwm-omap-dmtimer.c | 6 +-----
>  1 file changed, 1 insertion(+), 5 deletions(-)
> 
> diff --git a/drivers/pwm/pwm-omap-dmtimer.c b/drivers/pwm/pwm-omap-dmtimer.c
> index 103d729..8c9953c 100644
> --- a/drivers/pwm/pwm-omap-dmtimer.c
> +++ b/drivers/pwm/pwm-omap-dmtimer.c
> @@ -49,11 +49,7 @@ to_pwm_omap_dmtimer_chip(struct pwm_chip *chip)
>  
>  static u32 pwm_omap_dmtimer_get_clock_cycles(unsigned long clk_rate, int ns)
>  {
> -	u64 c = (u64)clk_rate * ns;
> -
> -	do_div(c, NSEC_PER_SEC);
> -
> -	return c;
> +	return DIV_ROUND_CLOSEST_ULL((u64)clk_rate * ns, NSEC_PER_SEC);
>  }
>  
>  static void pwm_omap_dmtimer_start(struct pwm_omap_dmtimer_chip *omap)
> 

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Thierry Reding March 4, 2016, 3:18 p.m. UTC | #2 
On Fri, Jan 29, 2016 at 11:26:53PM -0500, David Rivshin (Allworx) wrote:
> From: David Rivshin <drivshin@allworx.com>
> 
> When converting period and duty_cycle from nanoseconds to fclk cycles,
> the error introduced by the integer division can be appreciable, especially
> in the case of slow fclk or short period. Use DIV_ROUND_CLOSEST_ULL() so
> that the error is kept to +/- 0.5 clock cycles.
> 
> Fixes: 6604c6556db9 ("pwm: Add PWM driver for OMAP using dual-mode timers")
> Signed-off-by: David Rivshin <drivshin@allworx.com>
> ---
>  drivers/pwm/pwm-omap-dmtimer.c | 6 +-----
>  1 file changed, 1 insertion(+), 5 deletions(-)

Applied, thanks.

Thierry
diff mbox

Patch

diff --git a/drivers/pwm/pwm-omap-dmtimer.c b/drivers/pwm/pwm-omap-dmtimer.c
index 103d729..8c9953c 100644
--- a/drivers/pwm/pwm-omap-dmtimer.c
+++ b/drivers/pwm/pwm-omap-dmtimer.c
@@ -49,11 +49,7 @@  to_pwm_omap_dmtimer_chip(struct pwm_chip *chip)
 
 static u32 pwm_omap_dmtimer_get_clock_cycles(unsigned long clk_rate, int ns)
 {
-	u64 c = (u64)clk_rate * ns;
-
-	do_div(c, NSEC_PER_SEC);
-
-	return c;
+	return DIV_ROUND_CLOSEST_ULL((u64)clk_rate * ns, NSEC_PER_SEC);
 }
 
 static void pwm_omap_dmtimer_start(struct pwm_omap_dmtimer_chip *omap)