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

[neil.armstrong@linaro.org]

On 27/08/2024 17:36, Doug Anderson wrote:
> Hi,
> 
> On Mon, Jul 22, 2024 at 8:49 AM Doug Anderson <dianders@chromium.org> wrote:
>>
>> Hi,
>>
>> On Mon, Jul 15, 2024 at 6:51 AM Doug Anderson <dianders@chromium.org> wrote:
>>>
>>> Hi,
>>>
>>> On Mon, Jul 15, 2024 at 6:02 AM Neil Armstrong
>>> <neil.armstrong@linaro.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@chromium.org>
>>>>>>> Signed-off-by: Stephan Gerhold <stephan.gerhold@linaro.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.
>>
>> For now I'm going to snooze this patch for a month just to avoid any
>> controversy. I'll plan to apply it (to drm-misc-next) when I see the
>> device tree patch land. Since the device tree patch should land as a
>> fix that should keep things landing in the correct order. ...and, as
>> per above, the worst case is that if someone has an old DTS and a new
>> kernel then a panel that was already not working well will print a fat
>> warning and startup a bit slower.
>>
>> If somehow I mess up and forget about this patch, feel free to send me
>> a poke when the device tree patch is landed.
> 
> More than a month has passed now. One last warning before I apply this
> revert in a few more days.

It's fine if you apply it now

Neil

> 
> -Doug
>