linux-kernel - RE: [PATCH v23 3/4] pwm: Add support for RZ/G2L GPT

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Message-ID:
 <TYCPR01MB11332CCA52D52AA982BCDBFA486C22@TYCPR01MB11332.jpnprd01.prod.outlook.com>
Date: Wed, 26 Feb 2025 09:20:40 +0000
From: Biju Das <biju.das.jz@...renesas.com>
To: Uwe Kleine-König <ukleinek@...nel.org>
CC: kernel test robot <lkp@...el.com>, Philipp Zabel <p.zabel@...gutronix.de>,
	"oe-kbuild-all@...ts.linux.dev" <oe-kbuild-all@...ts.linux.dev>, Geert
 Uytterhoeven <geert+renesas@...der.be>, Magnus Damm <magnus.damm@...il.com>,
	"linux-pwm@...r.kernel.org" <linux-pwm@...r.kernel.org>,
	"linux-renesas-soc@...r.kernel.org" <linux-renesas-soc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Prabhakar
 Mahadev Lad <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: RE: [PATCH v23 3/4] pwm: Add support for RZ/G2L GPT

Hi Uwe,

Thanks for the feedback.

> -----Original Message-----
> From: Uwe Kleine-König <ukleinek@...nel.org>
> Sent: 21 February 2025 09:08
> Subject: Re: [PATCH v23 3/4] pwm: Add support for RZ/G2L GPT
> 
> Hello Biju,
> 
> On Thu, Jan 09, 2025 at 09:32:58AM +0000, Biju Das wrote:
> > > On Wed, Jan 08, 2025 at 02:13:09PM +0000, Biju Das wrote:
> > > > Please let me know, if there is any feedback for this patch series
> > > > or any new API to be adapted in next kernel version which
> > > > simplifies the code, So that I can send next
> > > version.
> > >
> > > I didn't look, but if you're ambitious you can convert your driver to the waveform callbacks.
> >
> > Is it ok, after the acceptance of initial version, will switch to
> > waveform callbacks to enable the users of GPT(Reason: lot of customers are using GPT for backlight
> for LCD panels)?
> >
> > Please let me know.
> 
> I'd still accept your driver with the legacy callbacks, mostly because your effort is already that old
> (which I consider my fault mostly).

OK. 

> 
> > Is there any documentation available for waveform callback? What
> > scenarios we can use Waveform callbacks compared to traditional one?
> 
> There is no nice documentation available yet. The improvements include:
> 
>  - arbitrary offsets for the duty cycle, so the active phase doesn't
>    need to be at the start or the end of a period any more
>  - consumers can query the result of a configuration request (before and
>    also after the request was issued).
> 
> Both are of little importance if your focus is mostly backlights.

Mostly RZ/G2L GPT users are backlights. So, from RZ/G2L usecase point, legacy
callback is sufficient.

Later, I will switch to waveform callbacks, for complex GPT usecase support for next
SoCs(eg: RZ/G3E).

Cheers,
Biju