| Message ID | 20201216174309.1604658-1-thierry.reding@gmail.com |
|---|---|
| State | Accepted |
| Commit | 6eefb79d6f5bc4086bd02c76f1072dd4a8d9d9f6 |
| Headers | show |
| Series | pwm: sun4i: Remove erroneous else branch | expand |
On Wed, Dec 16, 2020 at 06:43:09PM +0100, Thierry Reding wrote: > Commit d3817a647059 ("pwm: sun4i: Remove redundant needs_delay") changed > the logic of an else branch so that the PWM_EN and PWM_CLK_GATING bits > are now cleared if the PWM is to be disabled, whereas previously the > condition was always false, and hence the branch never got executed. > > This code is reported causing backlight issues on boards based on the > Allwinner A20 SoC. Fix this by removing the else branch, which restores > the behaviour prior to the offending commit. > > Note that the PWM_EN and PWM_CLK_GATING bits still get cleared later in > sun4i_pwm_apply() if the PWM is to be disabled. > > Fixes: d3817a647059 ("pwm: sun4i: Remove redundant needs_delay") > Reported-by: Taras Galchenko <tpgalchenko@gmail.com> This report didn't happen on the linux-pwm list, or did I miss it? What is the reported problem? I would expect a short time where the backlight goes off completely (or on depending on polarity?) when only a small continuous change is expected. > Suggested-by: Taras Galchenko <tpgalchenko@gmail.com> > Signed-off-by: Thierry Reding <thierry.reding@gmail.com> Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> Best regards Uwe
diff --git a/drivers/pwm/pwm-sun4i.c b/drivers/pwm/pwm-sun4i.c index cc1eb0818648..ce5c4fc8da6f 100644 --- a/drivers/pwm/pwm-sun4i.c +++ b/drivers/pwm/pwm-sun4i.c @@ -294,12 +294,8 @@ static int sun4i_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm, ctrl |= BIT_CH(PWM_CLK_GATING, pwm->hwpwm); - if (state->enabled) { + if (state->enabled) ctrl |= BIT_CH(PWM_EN, pwm->hwpwm); - } else { - ctrl &= ~BIT_CH(PWM_EN, pwm->hwpwm); - ctrl &= ~BIT_CH(PWM_CLK_GATING, pwm->hwpwm); - } sun4i_pwm_writel(sun4i_pwm, ctrl, PWM_CTRL_REG);
Commit d3817a647059 ("pwm: sun4i: Remove redundant needs_delay") changed the logic of an else branch so that the PWM_EN and PWM_CLK_GATING bits are now cleared if the PWM is to be disabled, whereas previously the condition was always false, and hence the branch never got executed. This code is reported causing backlight issues on boards based on the Allwinner A20 SoC. Fix this by removing the else branch, which restores the behaviour prior to the offending commit. Note that the PWM_EN and PWM_CLK_GATING bits still get cleared later in sun4i_pwm_apply() if the PWM is to be disabled. Fixes: d3817a647059 ("pwm: sun4i: Remove redundant needs_delay") Reported-by: Taras Galchenko <tpgalchenko@gmail.com> Suggested-by: Taras Galchenko <tpgalchenko@gmail.com> Signed-off-by: Thierry Reding <thierry.reding@gmail.com> --- drivers/pwm/pwm-sun4i.c | 6 +----- 1 file changed, 1 insertion(+), 5 deletions(-)