linux-kernel - Re: [PATCH v2] pwm: tiehrpwm: Enable EHRPWM controller before setting configuration

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Message-ID: <29dc86d5-080c-4af2-8e19-99a137c55f2f@ti.com>
Date: Mon, 19 Jan 2026 20:30:08 +0530
From: "Kumar, Udit" <u-kumar1@...com>
To: Uwe Kleine-König <ukleinek@...nel.org>, Gokul Praveen
	<g-praveen@...com>
CC: "Rafael V. Volkmer" <rafael.v.volkmer@...il.com>, <j-keerthy@...com>,
	<linux-kernel@...r.kernel.org>, <linux-pwm@...r.kernel.org>,
	<n-francis@...com>, <u-kumar1@...com>
Subject: Re: [PATCH v2] pwm: tiehrpwm: Enable EHRPWM controller before setting
 configuration

Hi Uwe/Gokul,

On 1/12/2026 12:52 PM, Uwe Kleine-König wrote:
> Hello Gokul,
>
> On Mon, Jan 12, 2026 at 11:21:50AM +0530, Gokul Praveen wrote:
>> On 10/01/26 04:23, Uwe Kleine-König wrote:
>>> As I cannot reproduce the issue, can you please check if adding
>>>
>>> 	pm_runtime_get_sync(pwmchip_parent(chip));
>>>
>>> to the probe function makes the problem disappear? Also please boot with
>>>
>>> 	trace_event=pwm
>>>
>>> on the command line and provide the content of
>>> /sys/kernel/debug/tracing/trace after reproducing the problem.
>> sure Uwe, I will try this from my side.
>>
>> In the meantime, will you able to test the same on TI J784S4 EVM as the
>> issue was reproduced on this board.
> I don't have such hardware, sorry. The boards with TI SoC on my desk are
> only a Beaglebone Black and a BeaglePlay. (And I didn't setup the
> BeaglePlay yet, it was already quite a hassle to make the boneblack work
> with a recent kernel. In the end it looks trivial, but
> https://salsa.debian.org/kernel-team/linux/-/merge_requests/1777 plus
> unreliable netbooting in the bootloader took me several hours to sort
> out.)

I am able to see this issue on J7200 hardware ,

LTM, it may work on certain devices, depending upon how LPSC (Local 
power state controller) and PSC (power state controller))

are managed.

In original code , while putting sync at

https://elixir.bootlin.com/linux/v6.18.6/source/drivers/pwm/pwm-tiehrpwm.c#L293 


will leads to calling genpd driver [0], which may put PWM IP in powered 
down state, leading to loosing contents.

So, we need retain pm count (genpd on in fact) between config and enable 
call.

Therefore this patch LGTM

https://gist.github.com/uditkumarti/6e36ca14423afc06378b8fa447ca3fe6




> Best regards
> Uwe