linux-kernel - Re: [PATCH v2 2/4] Revert "drm/panel-edp: Add SDC ATNA45AF01"

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Message-ID: <ZpUcI3KkIa58zC55@linaro.org>
Date: Mon, 15 Jul 2024 14:54:59 +0200
From: Stephan Gerhold <stephan.gerhold@...aro.org>
To: Neil Armstrong <neil.armstrong@...aro.org>
Cc: Bjorn Andersson <andersson@...nel.org>,
	Konrad Dybcio <konrad.dybcio@...aro.org>,
	Jessica Zhang <quic_jesszhan@...cinc.com>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Douglas Anderson <dianders@...omium.org>,
	dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
	Abel Vesa <abel.vesa@...aro.org>, Johan Hovold <johan@...nel.org>
Subject: Re: [PATCH v2 2/4] Revert "drm/panel-edp: Add SDC ATNA45AF01"

On Mon, Jul 15, 2024 at 02:42:12PM +0200, Neil Armstrong wrote:
> On 15/07/2024 14:15, Stephan Gerhold wrote:
> > This reverts commit 8ebb1fc2e69ab8b89a425e402c7bd85e053b7b01.
> > 
> > The panel should be handled through the samsung-atna33xc20 driver for
> > correct power up timings. Otherwise the backlight does not work correctly.
> > 
> > We have existing users of this panel through the generic "edp-panel"
> > compatible (e.g. the Qualcomm X1E80100 CRD), but the screen works only
> > partially in that configuration: It works after boot but once the screen
> > gets disabled it does not turn on again until after reboot. It behaves the
> > same way with the default "conservative" timings, so we might as well drop
> > the configuration from the panel-edp driver. That way, users with old DTBs
> > will get a warning and can move to the new driver.
> > 
> > Reviewed-by: Douglas Anderson <dianders@...omium.org>
> > Signed-off-by: Stephan Gerhold <stephan.gerhold@...aro.org>
> > ---
> >   drivers/gpu/drm/panel/panel-edp.c | 2 --
> >   1 file changed, 2 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/panel/panel-edp.c b/drivers/gpu/drm/panel/panel-edp.c
> > index 3a574a9b46e7..d2d682385e89 100644
> > --- a/drivers/gpu/drm/panel/panel-edp.c
> > +++ b/drivers/gpu/drm/panel/panel-edp.c
> > @@ -1960,8 +1960,6 @@ static const struct edp_panel_entry edp_panels[] = {
> >   	EDP_PANEL_ENTRY('L', 'G', 'D', 0x05af, &delay_200_500_e200_d200, "Unknown"),
> >   	EDP_PANEL_ENTRY('L', 'G', 'D', 0x05f1, &delay_200_500_e200_d200, "Unknown"),
> > -	EDP_PANEL_ENTRY('S', 'D', 'C', 0x416d, &delay_100_500_e200, "ATNA45AF01"),
> > -
> >   	EDP_PANEL_ENTRY('S', 'H', 'P', 0x1511, &delay_200_500_e50, "LQ140M1JW48"),
> >   	EDP_PANEL_ENTRY('S', 'H', 'P', 0x1523, &delay_80_500_e50, "LQ140M1JW46"),
> >   	EDP_PANEL_ENTRY('S', 'H', 'P', 0x153a, &delay_200_500_e50, "LQ140T1JH01"),
> > 
> 
> How will we handle current/old crd DT with new kernels ?
> 

I think this is answered in the commit message:

> > We have existing users of this panel through the generic "edp-panel"
> > compatible (e.g. the Qualcomm X1E80100 CRD), but the screen works only
> > partially in that configuration: It works after boot but once the screen
> > gets disabled it does not turn on again until after reboot. It behaves the
> > same way with the default "conservative" timings, so we might as well drop
> > the configuration from the panel-edp driver. That way, users with old DTBs
> > will get a warning and can move to the new driver.

Basically with the entry removed, the panel-edp driver will fallback to
default "conservative" timings when using old DTBs. There will be a
warning in dmesg, but otherwise the panel will somewhat work just as
before. I think this is a good way to remind users to upgrade.

> Same question for patch 3, thie serie introduces a bindings that won't be valid
> if we backport patch 3. I don't think patch should be backported, and this patch
> should be dropped.

There would be a dtbs_check warning, yeah. Functionally, it would work
just fine. Is that reason enough to keep display partially broken for
6.11? We could also apply the minor binding change for 6.11 if needed.

I'm also fine if this just goes into 6.12 though.

Thanks,
Stephan