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    SubjectRe: [PATCH 13/13] thermal/drivers/hisi: Remove mutex_lock in the code
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    On 02/09/2017 06:04, Leo Yan wrote:
    > 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.

    Great, thanks for testing this.

    >> 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
    >>


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