Message-ID: <6f8f902b-8192-492a-8354-18590c6c2c06@linaro.org>
Date: Mon, 15 Jul 2024 15:57:30 +0200
From: neil.armstrong@...aro.org
To: Doug Anderson <dianders@...omium.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"

On 15/07/2024 15:51, Doug Anderson wrote:
> 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?

Not sure the Soc maintainer would accept any patches for -rc1 at this
point, but Bjorn can try to push both #3 and #4 as fixes for -rc2.

Not sure #1 would be accepted as fix via any tree, but having a bindings
error for a kernel release is not a big deal if in-fine the bindings change
has been reviewed and queued for next version.

Basically when the -rc is tagged it gets backmerged into drm-misc-next,
so we can backmerge any -rc we want.

> 
> 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.

We can push it now to drm-misc-next so it gets naturally delayed until v6.12

Neil

> 
> -Doug
> 

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