linux-kernel - Re: [RFC PATCH] drm/panel: synaptics-r63353: Fix regulator unbalance

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Message-ID: <CAOf5uwkkggf9ooNWuNxmN2Xn_KKPW_XRVsYy4eUo91WU0M0rWw@mail.gmail.com>
Date: Wed, 7 Aug 2024 23:05:44 +0200
From: Michael Nazzareno Trimarchi <michael@...rulasolutions.com>
To: Doug Anderson <dianders@...omium.org>
Cc: neil.armstrong@...aro.org, quic_jesszhan@...cinc.com, sam@...nborg.org, 
	mripard@...nel.org, tzimmermann@...e.de, airlied@...il.com, daniel@...ll.ch, 
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] drm/panel: synaptics-r63353: Fix regulator unbalance

Hi Doug

On Wed, Aug 7, 2024 at 11:02 PM Doug Anderson <dianders@...omium.org> wrote:
>
> Hi,
>
> On Wed, Aug 7, 2024 at 5:39 AM Michael Nazzareno Trimarchi
> <michael@...rulasolutions.com> wrote:
> >
> > Hi Doug
> >
> > +cc Doug
> >
> > I have seen that you have done some re-working and investigation on
> > drm stack, do you have some
> > suggestion on this case?
> >
> > On Mon, Jun 24, 2024 at 8:53 PM Michael Trimarchi
> > <michael@...rulasolutions.com> wrote:
> > >
> > > The shutdown function can be called when the display is already
> > > unprepared. For example during reboot this trigger a kernel
> > > backlog. Calling the drm_panel_unprepare, allow us to avoid
> > > to trigger the kernel warning
> > >
> > > Signed-off-by: Michael Trimarchi <michael@...rulasolutions.com>
> > > ---
> > >
> > > It's not obviovus if shutdown can be dropped or this problem depends
> > > on the display stack as it is implmented. More feedback is required
> > > here
>
> In general the shutdown should be dropped and it should be up to the
> display driver to do the shutdown. If your panel needs to be used with
> a DRM Modeset driver that doesn't properly call shutdown then the
> ideal solution would be to fix the DRM Modeset driver. If this is
> somehow impossible, I suspect folks would (begrudgingly) accept some
> other solution.
>
> From a super quick look, I see:
>
> * This panel seems to be used upstream by "imx8mn-bsh-smm-s2-display.dtsi"
>
> * In "imx8mn.dtsi" I see "lcdif" is "fsl,imx6sx-lcdif".
>
> * "fsl,imx6sx-lcdif" seems to be handled by "drivers/gpu/drm/mxsfb/mxsfb_drv.c"
>
> * Previously I determined that "mxsfb-drm" was indeed calling
> drm_atomic_helper_shutdown() properly [1]
>
> ...so it seems like just dropping the shutdown handler in this panel is correct.
>
>
> [1] https://lore.kernel.org/r/20240611074846.1.Ieb287c2c3ee3f6d3b0d5f49b29f746b93621749c@changeid
>

Good, that is the information I need to know, I have read some of your
threads and it's ok for me to just drop it.
I will resend a proper patch for it

Michael

> -Doug



-- 
Michael Nazzareno Trimarchi
Co-Founder & Chief Executive Officer
M. +39 347 913 2170
michael@...rulasolutions.com
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