| Message ID | 1429034708-4537-1-git-send-email-linux.amoon@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, 2015-04-15 at 03:35 +0930, Anand Moon wrote: > diff --git a/drivers/pwm/pwm-samsung.c b/drivers/pwm/pwm-samsung.c > index 3e9b583..b579753 100644 > --- a/drivers/pwm/pwm-samsung.c > +++ b/drivers/pwm/pwm-samsung.c > @@ -247,6 +247,7 @@ static int pwm_samsung_enable(struct pwm_chip *chip, struct pwm_device *pwm) > tcon &= ~TCON_MANUALUPDATE(tcon_chan); > tcon |= TCON_START(tcon_chan) | TCON_AUTORELOAD(tcon_chan); > writel(tcon, our_chip->base + REG_TCON); > + clk_prepare_enable(our_chip->base_clk); > > spin_unlock_irqrestore(&samsung_pwm_lock, flags); > > @@ -265,6 +266,7 @@ static void pwm_samsung_disable(struct pwm_chip *chip, struct pwm_device *pwm) > tcon = readl(our_chip->base + REG_TCON); > tcon &= ~TCON_AUTORELOAD(tcon_chan); > writel(tcon, our_chip->base + REG_TCON); > + clk_disable_unprepare(our_chip->base_clk); > > spin_unlock_irqrestore(&samsung_pwm_lock, flags); > } As far as i can tell this code doesn't have any effect. clk_enable is refcounted, so the clock will stay enabled for as long as the driver is loaded (as it's enabled in _probe). Your code above just raises and lowers the clocks enabled refcount, but won't actually ever cause it to be disabled. With respect to trying to disabling the clocks on pwm_disable, that will need some more work to ensure the output signal has the expected level when you turn of the clock. Specifically, when disabling from a non-100% duty state the driver relies on the PWM turning the output signal low at the end of a duty cycle. However if you turn off the clock at the start of a duty cycle while the output signal is still high it will unexpectedly remain high.
hi Sjoerd, Are you referring to handle of polarity (PWM_POLARITY_NORMAL/PWM_POLARITY_INVERSED) during enable and disable. How can I analyses if the clock is high and low. -Anand Moon On 15 April 2015 at 14:04, Sjoerd Simons <sjoerd.simons@collabora.co.uk> wrote: > On Wed, 2015-04-15 at 03:35 +0930, Anand Moon wrote: >> diff --git a/drivers/pwm/pwm-samsung.c b/drivers/pwm/pwm-samsung.c >> index 3e9b583..b579753 100644 >> --- a/drivers/pwm/pwm-samsung.c >> +++ b/drivers/pwm/pwm-samsung.c >> @@ -247,6 +247,7 @@ static int pwm_samsung_enable(struct pwm_chip *chip, struct pwm_device *pwm) >> tcon &= ~TCON_MANUALUPDATE(tcon_chan); >> tcon |= TCON_START(tcon_chan) | TCON_AUTORELOAD(tcon_chan); >> writel(tcon, our_chip->base + REG_TCON); >> + clk_prepare_enable(our_chip->base_clk); >> >> spin_unlock_irqrestore(&samsung_pwm_lock, flags); >> >> @@ -265,6 +266,7 @@ static void pwm_samsung_disable(struct pwm_chip *chip, struct pwm_device *pwm) >> tcon = readl(our_chip->base + REG_TCON); >> tcon &= ~TCON_AUTORELOAD(tcon_chan); >> writel(tcon, our_chip->base + REG_TCON); >> + clk_disable_unprepare(our_chip->base_clk); >> >> spin_unlock_irqrestore(&samsung_pwm_lock, flags); >> } > > As far as i can tell this code doesn't have any effect. > > clk_enable is refcounted, so the clock will stay enabled for as long as > the driver is loaded (as it's enabled in _probe). Your code above just > raises and lowers the clocks enabled refcount, but won't actually ever > cause it to be disabled. > > With respect to trying to disabling the clocks on pwm_disable, that will > need some more work to ensure the output signal has the expected level > when you turn of the clock. Specifically, when disabling from a non-100% > duty state the driver relies on the PWM turning the output signal low at > the end of a duty cycle. However if you turn off the clock at the start > of a duty cycle while the output signal is still high it will > unexpectedly remain high. > > > -- > Sjoerd Simons <sjoerd.simons@collabora.co.uk> > Collabora Ltd. -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/pwm/pwm-samsung.c b/drivers/pwm/pwm-samsung.c index 3e9b583..b579753 100644 --- a/drivers/pwm/pwm-samsung.c +++ b/drivers/pwm/pwm-samsung.c @@ -247,6 +247,7 @@ static int pwm_samsung_enable(struct pwm_chip *chip, struct pwm_device *pwm) tcon &= ~TCON_MANUALUPDATE(tcon_chan); tcon |= TCON_START(tcon_chan) | TCON_AUTORELOAD(tcon_chan); writel(tcon, our_chip->base + REG_TCON); + clk_prepare_enable(our_chip->base_clk); spin_unlock_irqrestore(&samsung_pwm_lock, flags); @@ -265,6 +266,7 @@ static void pwm_samsung_disable(struct pwm_chip *chip, struct pwm_device *pwm) tcon = readl(our_chip->base + REG_TCON); tcon &= ~TCON_AUTORELOAD(tcon_chan); writel(tcon, our_chip->base + REG_TCON); + clk_disable_unprepare(our_chip->base_clk); spin_unlock_irqrestore(&samsung_pwm_lock, flags); }
It's safe to disable the clk when we following. pwm_config(pwm, 0, period); pwm_disable(pwm); And enable clk when we do following. pwm_config(pwm, duty, period); pwm_enable(pwm); Tested on OdroidXU3 Board. Signed-off-by: Anand Moon <linux.amoon@gmail.com> --- drivers/pwm/pwm-samsung.c | 2 ++ 1 file changed, 2 insertions(+)