Re: [PATCH] pwm: Call pwm_enable() before pwm_config()

On Friday, August 24, 2012 12:44 AM, Lars-Peter Clausen wrote:

On 08/23/2012 04:19 PM, Benoît Thébaudeau wrote:

quoted

Some PWM drivers enable the clock of the PWM peripheral in pwm_enable(). Hence,
for these drivers, a call to pwm_config() does not have any effect before
pwm_enable() has been called.

This patch fixes the PWM users to make sure that they call pwm_enable() before
pwm_config().

This fixes the first setting of brightness through sysfs that had no effect with
leds-pwm and the i.MX PWM driver.

But isn't this a bug in the PWM peripheral driver? With this change the PWM
will start with the old settings first. While this is not so much of a problem
for a backlight (although it might cause a short flickering) it might cause
problems for other applications, like using the PWM pin as a timing generator.
In my opinion it's better to fix the PWM peripheral drivers which have this
problem instead of trying to work around it in every user of the PWM API.

Hi Lars-Peter Clausen,

I think so.
It would be better to fix the PWM peripheral drivers.


Best regards,
Jingoo Han

- Lars
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