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From: pratikmanvar09@gmail.com
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Subject: Re: [PATCH v3] pwm: imx27: workaround of the pwm output bug
Date: Tue,  5 Mar 2024 14:57:29 +0530
In-Reply-To: <20240103110200.1018-1-pratikmanvar09@gmail.com>
References: <20240103122005.GA3347@francesco-nb>
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Hello Francesco,=0D
=0D
Sorry for the abysmal delay.=0D
Thanks for your review and suggestions.=0D
=0D
>Hello Pratik,=0D
>=0D
>On Wed, Jan 03, 2024 at 04:32:00PM +0530, pratikmanvar09@gmail.com wrote:=
=0D
>> From: Clark Wang <xiaoning.wang@nxp.com>=0D
>> =0D
>> This fixes the pwm output bug when decrease the duty cycle.=0D
>> This is a limited workaround for the PWM IP issue TKT0577206.=0D
>> =0D
>> Root cause:=0D
>> When the SAR FIFO is empty, the new write value will be directly applied=
=0D
>> to SAR even the current period is not over.=0D
>> If the new SAR value is less than the old one, and the counter is=0D
>> greater than the new SAR value, the current period will not filp the=0D
>> level. This will result in a pulse with a duty cycle of 100%.=0D
>> =0D
>> Workaround:=0D
>> Add an old value SAR write before updating the new duty cycle to SAR.=0D
>> This will keep the new value is always in a not empty fifo, and can be=0D
>> wait to update after a period finished.=0D
>> =0D
>> Limitation:=0D
>> This workaround can only solve this issue when the PWM period is longer=
=0D
>> than 2us(or <500KHz).=0D
>> =0D
>> Reviewed-by: Jun Li <jun.li@nxp.com>=0D
>> Signed-off-by: Clark Wang <xiaoning.wang@nxp.com>=0D
>> Link: https://github.com/nxp-imx/linux-imx/commit/16181cc4eee61d87cbaba0=
e5a479990507816317=0D
>> Tested-by: Pratik Manvar <pratik.manvar@ifm.com>=0D
>> Signed-off-by: Pratik Manvar <pratik.manvar@ifm.com>=0D
>=0D
>A very similar patch was already send in 2021 [1], did it had review=0D
>comments not addressed? Please have a look.=0D
>=0D
>In general please refrain from sending a new patch version every other=0D
>day, while every Linux kernel subsystem has different rules and a=0D
>difference pace of development, in this specific case sending a v3 just=0D
>adding your signed-off-by without allowing a little bit of time to wait=0D
>for more feedback is just not sane.=0D
Ok, I will keep this in mind. Thanks!=0D
>=0D
>[1] https://lore.kernel.org/all/?q=3Ddfn%3Adrivers%2Fpwm%2Fpwm-imx27.c+AND=
+b%3A%22Clark+Wang%22=0D
Ok, I did not check this. I will look into this. Thanks!=0D
=0D
Thanks & Regards,=0D
Pratik Manvar=