Re: [PATCH 13/13] thermal/drivers/hisi: Remove mutex_lock in the code

Leo Yan
2017-09-02T04:05:07Z

On Wed, Aug 30, 2017 at 10:47:37AM +0200, Daniel Lezcano wrote:
> The mutex is used to protect against writes in the configuration register.
>
> That happens at probe time, with no possible race yet.
>
> Then when the module is unloaded and at suspend/resume.
>
> When the module is unloaded, it is an userspace operation, thus via a process.
> Suspending the system goes through the freezer to suspend all the tasks
> synchronously before continuing. So it is not possible to hit the suspend ops
> in this driver while we are unloading it.
>
> The resume is the same situation than the probe.
>
> In other words, even if there are several places where we write the
> configuration register, there is no situation where we can write it at the same
> time, so far as I can judge

After applied your previous patches, configuration reigster accessing
only happens in the probe and resume functions. So shouldn't have
chance to access it at the same time.

BTW, I verified this patch with system suspend/resume, so far it works
well after system resume back.

> Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>

Reviewed-by: Leo Yan <leo.yan@linaro.org>
Tested-by: Leo Yan <leo.yan@linaro.org>

> ---
> drivers/thermal/hisi_thermal.c | 6 ------
> 1 file changed, 6 deletions(-)
>
> diff --git a/drivers/thermal/hisi_thermal.c b/drivers/thermal/hisi_thermal.c
> index b1b086ab..b9e8ee2 100644
> --- a/drivers/thermal/hisi_thermal.c
> +++ b/drivers/thermal/hisi_thermal.c
> @@ -51,7 +51,6 @@ struct hisi_thermal_sensor {
> };
>
> struct hisi_thermal_data {
> - struct mutex thermal_lock; /* protects register data */
> struct platform_device *pdev;
> struct clk *clk;
> struct hisi_thermal_sensor sensor;
> @@ -196,14 +195,10 @@ static inline void hisi_thermal_hdak_set(void __iomem *addr, int value)
>
> static void hisi_thermal_disable_sensor(struct hisi_thermal_data *data)
> {
> - mutex_lock(&data->thermal_lock);
> -
> /* disable sensor module */
> hisi_thermal_enable(data->regs, 0);
> hisi_thermal_alarm_enable(data->regs, 0);
> hisi_thermal_reset_enable(data->regs, 0);
> -
> - mutex_unlock(&data->thermal_lock);
> }
>
> static int hisi_thermal_get_temp(void *__data, int *temp)
> @@ -340,7 +335,6 @@ static int hisi_thermal_probe(struct platform_device *pdev)
> if (!data)
> return -ENOMEM;
>
> - mutex_init(&data->thermal_lock);
> data->pdev = pdev;
>
> res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> --
> 2.7.4
>