Messages in this thread | | | Date | Thu, 19 Jan 2017 15:49:25 +0100 | From | Clemens Gruber <> | Subject | Re: [PATCH 2/2] pwm: pca9685: fix prescaler initialization |
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On Thu, Jan 19, 2017 at 02:34:39PM +0200, Andy Shevchenko wrote: > On Wed, 2017-01-18 at 15:25 +0100, Clemens Gruber wrote: > > Yes, that's what this patch tries to solve by verifying that the > > external setting (the prescale register) is set to its hardware > > default > > value of 0x1E (corresponding to a period of 1/200 Hz). > > If it is not 0x1E, the driver will reconfigure the prescaler according > > to the desired period at the time of the next configuration. > > Yes, and my question is what is possible go wrong if you just enforce > prescaler to be 1/200Hz?
If we enforce a default of 1 / 200 Hz, we have to go through the SLEEP mode and udelay for 0.5ms once for our default and then again for the user, if he does not want a period of 1 / 200 Hz. -> Number of prescaler changes: 1 or 2
I think it is better as it is now + my patch applied: We verify if the prescaler is already set to 1 / 200 Hz. Then, as soon as the user configures his PWM channels, we either do not have to change the prescaler at all (if he wants 1 / 200 Hz) or do it once at the time of configuration. -> Number of prescaler changes: 0 or 1
What's the advantage of enforcing the prescaler to 1 / 200 Hz in the probe function when we do not know yet if 1 / 200 Hz is the period the user is going to configure?
Thanks, Clemens
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