Hi Uwe,
On 2021/11/30, 4:21 PM, "Uwe Kleine-König" <u.kleine-koenig@xxxxxxxxxxxxxx> wrote:
Hello,
On Tue, Nov 30, 2021 at 11:00:46AM +0800, Billy Tsai wrote:
> > This patch is used to fix the bug when pwm_fan_probe the pwm_value will
> > be out of sync with the PWM hardware drivers.
> >
> > Fixes: 86585c61972f ("hwmon: (pwm-fan) stop using legacy PWM functions and some cleanups")
> > Signed-off-by: Billy Tsai <billy_tsai@xxxxxxxxxxxxxx>
> > ---
> > drivers/hwmon/pwm-fan.c | 2 --
> > 1 file changed, 2 deletions(-)
> >
> > diff --git a/drivers/hwmon/pwm-fan.c b/drivers/hwmon/pwm-fan.c
> > index 17518b4cab1b..f12b9a28a232 100644
> > --- a/drivers/hwmon/pwm-fan.c
> > +++ b/drivers/hwmon/pwm-fan.c
> > @@ -336,8 +336,6 @@ static int pwm_fan_probe(struct platform_device *pdev)
> > return ret;
> > }
> >
> > - ctx->pwm_value = MAX_PWM;
> > -
> > pwm_init_state(ctx->pwm, &ctx->pwm_state);
> Ah, I see. The effect is that the FAN is supposed to be running at full
> speed after probe, but this isn't asserted.
> So the patch is fine, but I suggest to make the commit log a bit more
> frightening. Something like:
> hwmon: (pwm-fan) Ensure the fan going on in .probe()
> Before commit 86585c61972f ("hwmon: (pwm-fan) stop using legacy
> PWM functions and some cleanups") pwm_apply_state() was called
> unconditionally in pwm_fan_probe(). In this commit this direct
> call was replaced by a call to __set_pwm(ct, MAX_PWM) which
> however is a noop if ctx->pwm_value already matches the value to
> set.
> After probe the fan is supposed to run at full speed, and the
> internal driver state suggests it does, but this isn't asserted
> and depending on bootloader and pwm low-level driver, the fan
> might just be off.
> So drop setting pwm_value to MAXX_PWM to ensure the check in
> __set_pwm doesn't make it exit early and the fan goes on as
> intended.
> Cc: stable@xxxxxxxxxxxxxxx
> Fixes: 86585c61972f ("hwmon: (pwm-fan) stop using legacy PWM functions and some cleanups")
Ok, I will use this commit log and resend the patch.
Best Regards,
Billy Tsai
