Messages in this thread | ![/](/images/icornerl.gif) | | Date | Wed, 24 Jan 2024 12:48:21 +0100 | Subject | Re: [PATCH v3] pwm: imx27: workaround of the pwm output bug | From | Stefan Wahren <> |
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Hi,
Am 03.01.24 um 13:20 schrieb Francesco Dolcini: > Hello Pratik, > > On Wed, Jan 03, 2024 at 04:32:00PM +0530, pratikmanvar09@gmail.com wrote: >> From: Clark Wang <xiaoning.wang@nxp.com> >> >> This fixes the pwm output bug when decrease the duty cycle. >> This is a limited workaround for the PWM IP issue TKT0577206. >> >> Root cause: >> When the SAR FIFO is empty, the new write value will be directly applied >> to SAR even the current period is not over. >> If the new SAR value is less than the old one, and the counter is >> greater than the new SAR value, the current period will not filp the >> level. This will result in a pulse with a duty cycle of 100%. >> >> Workaround: >> Add an old value SAR write before updating the new duty cycle to SAR. >> This will keep the new value is always in a not empty fifo, and can be >> wait to update after a period finished. >> >> Limitation: >> This workaround can only solve this issue when the PWM period is longer >> than 2us(or <500KHz). >> >> Reviewed-by: Jun Li <jun.li@nxp.com> >> Signed-off-by: Clark Wang <xiaoning.wang@nxp.com> >> Link: https://github.com/nxp-imx/linux-imx/commit/16181cc4eee61d87cbaba0e5a479990507816317 >> Tested-by: Pratik Manvar <pratik.manvar@ifm.com> >> Signed-off-by: Pratik Manvar <pratik.manvar@ifm.com> > A very similar patch was already send in 2021 [1], did it had review > comments not addressed? Please have a look. > > In general please refrain from sending a new patch version every other > day, while every Linux kernel subsystem has different rules and a > difference pace of development, in this specific case sending a v3 just > adding your signed-off-by without allowing a little bit of time to wait > for more feedback is just not sane. > > [1] https://lore.kernel.org/all/?q=dfn%3Adrivers%2Fpwm%2Fpwm-imx27.c+AND+b%3A%22Clark+Wang%22 thank you, this is very helpful. Unfortunately i don't have the knowledge and resources to continue this work.
@Uwe It seems that you were able to reproduce this issue. Is it possible to trigger this via sysfs and some kind of script?
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