Re: [PATCH v3 33/43] drm/panel: simple: Change mode for Sharp lq123p1jx31

Enric Balletbo Serra
2018-02-19T09:42:48Z

Hi,

2018-02-16 21:54 GMT+01:00 Doug Anderson <dianders@chromium.org>:
> Hi,
>
> On Fri, Feb 16, 2018 at 4:34 AM, Enric Balletbo Serra
> <eballetbo@gmail.com> wrote:
>> Hi,
>>
>> 2018-01-31 17:52 GMT+01:00 Doug Anderson <dianders@chromium.org>:
>>> Hi,
>>>
>>>
>>> On Wed, Jan 31, 2018 at 7:16 AM, Sean Paul <seanpaul@chromium.org> wrote:
>>>> On Wed, Jan 31, 2018 at 7:54 AM, Lucas Stach <l.stach@pengutronix.de> wrote:
>>>>> Am Dienstag, den 30.01.2018, 21:29 +0100 schrieb Thierry Escande:
>>>>>> From: Sean Paul <seanpaul@chromium.org>
>>>>>>
>>>>>> Change the mode for Sharp lq123p1jx31 panel to something more
>>>>>> rockchip-friendly such that we can use the fixed PLLs to
>>>>>> generate the pixel clock
>>>>>
>>>>> This should really switch to a display timing instead of exposing a
>>>>> single mode. The display timing has min, typical, max tuples for all
>>>>> the timings values, which would allow the attached driver to vary the
>>>>> timings inside the allowed bounds if it makes sense.
>>>>>
>>>>> Trying to hit a specific pixel clock to free up a PLL is exactly one of
>>>>> the use cases envisioned for the display timings stuff.
>>>>>
>>>>
>>>> Agreed, I think we had this discussion the first time around. We
>>>> should drop this patch.
>>>>
>>>> Thanks for catching this!
>>>
>>> Are you sure we should drop this? In order for things to work
>>> properly (not generate noise on the digitizer or other EMI), this
>>> needs to run at a very specific pixel clock with very specific
>>> blanking times. I know that earlier we had slightly different
>>> blanking times and Samsung came back and said that there was noise on
>>> the digitizer. I could be wrong, but I don't think there's any way
>>> currently to be able to specify exactly what timings should be used on
>>> a particular board.
>>>
>>> Don't get be wrong--I think a patch such as this one that claims a
>>> single board's timings as the "right" ones for a generic panel is a
>>> bit of a hack. ...but at the same time there are no other users of
>>> this panel (that I know of) in mainline and the timings presented here
>>> are certainly sane timings for this panel.
>>>
>>> In any case, previous discussion at: https://patchwork.kernel.org/patch/9614603/
>>>
>>>
>>> ...oh, and looking at the previous discussion reminds me that the
>>> timings presented in this here patch are actually not the right ones
>>> (they have the right PLL, but the wrong blankings to avoid the noise
>>> issues). See <//chromium-review.googlesource.com/381015>
>>>
>>
>> As Thierry no longer has the hardware to test these patch series, I'll
>> take care of these and follow the upstreaming process. I think that
>> doesn't make sense send a v4 version of all 43 patches for this
>> change. Right now, only this patch received comments so I'll wait a
>> bit more for if we can get the other patches reviewed. If the others
>> are fine just and I don't need to send a new version just don't apply
>> this one and I will send a second version of that specific patch. Or
>> even better, is really trivial what needs to be changed, so maybe the
>> maintainer can do it? ;)
>
> Just as a heads up, Sean Paul has a series of patches to replace this
> patch. The following are IDs from patchwork.kernel.org:
>
> 10207583 New [v3,1/6] dt-bindings: Clarify timing subnode use
> as panel-timing
> 10207585 New [v3,2/6] dt-bindings: Add headings to
> simple-panel bindings
> 10207591 New [v3,3/6] dt-bindings: Add panel-timing subnode
> to simple-panel
> 10207593 New [v3,4/6] drm/panel: simple: Add ability to
> override typical timing
> 10207595 New [v3,5/6] drm/panel: simple: Use display_timing
> for lq123p1jx31
> 10207603 New [v3,6/6] arm64: dts: rockchip: Specify override
> mode for kevin panel
>
> -Doug

Nice, I was not aware of these, I'll test. That means that this patch
can be removed from these series as the Sean solution is a lot better.
Just a note that this patch can be removed without any collateral
impact on the other patches, so just ignore it.

Regards,
Enric