2018-04-10 08:18:24

by Jia-Ju Bai

Subject: [PATCH 1/3] thermal: armada_thermal: Replace mdelay with usleep_range in armada370_init_sensor

armada370_init_sensor() is never called in atomic context.

armada370_init_sensor() is set as ".init_sensor" in
struct armada_thermal_data.
".init_sensor" is called armada_thermal_probe().
armada_thermal_probe() is set as ".probe" in struct platform_driver.
This function is not called in atomic context.

Despite never getting called from atomic context, armada370_init_sensor()
calls mdelay() to busily wait.
This is not necessary and can be replaced with usleep_range() to
avoid busy waiting.

This is found by a static analysis tool named DCNS written by myself.
And I also manually check it.

Signed-off-by: Jia-Ju Bai <[email protected]>
---
drivers/thermal/armada_thermal.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/thermal/armada_thermal.c b/drivers/thermal/armada_thermal.c
index ae75328..807fe74 100644
--- a/drivers/thermal/armada_thermal.c
+++ b/drivers/thermal/armada_thermal.c
@@ -113,7 +113,7 @@ static void armada370_init_sensor(struct platform_device *pdev,
reg &= ~PMU_TDC0_START_CAL_MASK;
writel(reg, priv->control);

- mdelay(10);
+ usleep_range(10000, 11000);
}

static void armada375_init_sensor(struct platform_device *pdev,
--
1.9.1

2018-04-27 02:12:53

by Eduardo Valentin

Subject: Re: [PATCH 1/3] thermal: armada_thermal: Replace mdelay with usleep_range in armada370_init_sensor

Hey Jia-Ju,

On Tue, Apr 10, 2018 at 04:13:02PM +0800, Jia-Ju Bai wrote:
> armada370_init_sensor() is never called in atomic context.
>
> armada370_init_sensor() is set as ".init_sensor" in
> struct armada_thermal_data.
> ".init_sensor" is called armada_thermal_probe().
> armada_thermal_probe() is set as ".probe" in struct platform_driver.
> This function is not called in atomic context.
>
> Despite never getting called from atomic context, armada370_init_sensor()
> calls mdelay() to busily wait.
> This is not necessary and can be replaced with usleep_range() to
> avoid busy waiting.
>
> This is found by a static analysis tool named DCNS written by myself.
> And I also manually check it.
>
> Signed-off-by: Jia-Ju Bai <[email protected]>
> ---
> drivers/thermal/armada_thermal.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/thermal/armada_thermal.c b/drivers/thermal/armada_thermal.c
> index ae75328..807fe74 100644
> --- a/drivers/thermal/armada_thermal.c
> +++ b/drivers/thermal/armada_thermal.c
> @@ -113,7 +113,7 @@ static void armada370_init_sensor(struct platform_device *pdev,
> reg &= ~PMU_TDC0_START_CAL_MASK;
> writel(reg, priv->control);
>
> - mdelay(10);
> + usleep_range(10000, 11000);

Cool, but these have been already translated into msleep():
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/thermal/armada_thermal.c#n141


> }
>
> static void armada375_init_sensor(struct platform_device *pdev,
> --
> 1.9.1
>