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

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Message-ID: <CAD=FV=WimxYmDrkfn0+E3MbXp8kS9TicN2kT3AM4eM+SAwYsOg@mail.gmail.com>
Date: Mon, 15 Jul 2024 06:51:18 -0700
From: Doug Anderson <dianders@...omium.org>
To: neil.armstrong@...aro.org
Cc: Stephan Gerhold <stephan.gerhold@...aro.org>, 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>, 
	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"

Hi,

On Mon, Jul 15, 2024 at 6:02 AM Neil Armstrong
<neil.armstrong@...aro.org> wrote:
>
> On 15/07/2024 14:54, Stephan Gerhold wrote:
> > 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.
>
> I consider this as a regression
>
> >
> >> 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 don't know how to answer this, I'll let the DT maintainer comment this.
>
> The problem is I do not think we can pass the whole patchset as fixes
> for v6.11, patches 2 & 3 could, patches 1 & 4 definitely can't.
>
> Neil

IMO: patch #3 (dts) and #4 (CONFIG) go through the Qualcomm tree
whenever those folks agree to it. If we're worried about the
dtbs_check breakage I personally wouldn't mind "Ack"ing patch #1 to go
through the Qualcomm tree as long as it made it into 6.11-rc1. I have
a hunch that there are going to be more Samsung OLED panels in the
future that will need to touch the same file, but if the change is in
-rc1 it should make it back into drm-misc quickly, right?

Personally I think patch #2 could go in anytime since, as people have
said, things are pretty broken today and the worst that happens is
that someone gets an extra warning. That would be my preference. That
being said, we could also snooze that patch for a month or two and
land it later. There's no real hurry.

-Doug