linux-kernel - Re: [PATCH v1 2/2] drm/panel-simple: Add missing BUS descriptions for some panels

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Message-ID: <20200628080253.GD6954@pendragon.ideasonboard.com>
Date:   Sun, 28 Jun 2020 11:02:53 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Sam Ravnborg <sam@...nborg.org>
Cc:     Dmitry Osipenko <digetx@...il.com>,
        Thierry Reding <thierry.reding@...il.com>,
        dri-devel@...ts.freedesktop.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 2/2] drm/panel-simple: Add missing BUS descriptions
 for some panels

Hi Sam,

On Sun, Jun 28, 2020 at 09:52:45AM +0200, Sam Ravnborg wrote:
> On Sun, Jun 28, 2020 at 10:07:45AM +0300, Laurent Pinchart wrote:
> > On Sun, Jun 28, 2020 at 02:44:15AM +0300, Dmitry Osipenko wrote:
> >> 27.06.2020 23:43, Laurent Pinchart пишет:
> >>> On Mon, Jun 22, 2020 at 01:27:42AM +0300, Dmitry Osipenko wrote:
> >>>> This patch adds missing BUS fields to the display panel descriptions of
> >>>> the panels which are found on NVIDIA Tegra devices:
> >>>>
> >>>>   1. AUO B101AW03
> >>>>   2. Chunghwa CLAA070WP03XG
> >>>>   3. Chunghwa CLAA101WA01A
> >>>>   4. Chunghwa CLAA101WB01
> >>>>   5. Innolux N156BGE L21
> >>>>   6. Samsung LTN101NT05
> >>>>
> >>>> Suggested-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> >>>> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
> >>>> ---
> >>>>  drivers/gpu/drm/panel/panel-simple.c | 12 ++++++++++++
> >>>>  1 file changed, 12 insertions(+)
> >>>>
> >>>> diff --git a/drivers/gpu/drm/panel/panel-simple.c b/drivers/gpu/drm/panel/panel-simple.c
> >>>> index 87edd2bdf09a..986df9937650 100644
> >>>> --- a/drivers/gpu/drm/panel/panel-simple.c
> >>>> +++ b/drivers/gpu/drm/panel/panel-simple.c
> >>>> @@ -698,6 +698,8 @@ static const struct panel_desc auo_b101aw03 = {
> >>>>  		.width = 223,
> >>>>  		.height = 125,
> >>>>  	},
> >>>> +	.bus_format = MEDIA_BUS_FMT_RGB666_1X7X3_SPWG,
> >>>> +	.bus_flags = DRM_BUS_FLAG_DE_HIGH | DRM_BUS_FLAG_PIXDATA_DRIVE_POSEDGE,
> >>> 
> >>> Does DRM_BUS_FLAG_PIXDATA_DRIVE_* make sense for LVDS ?
> >> 
> >> To be honest I don't know whether it make sense or not for LVDS. I saw
> >> that other LVDS panels in panel-simple.c use the PIXDATA flag and then
> >> looked at what timing diagrams in the datasheets show.
> > 
> > I think we should drop DRM_BUS_FLAG_PIXDATA_DRIVE_* for LVDS panels.
> > I'll submit a patch.
> 
> We should also clean up all the DRM_BUS_FLAG_* one day.
> No need for the deprecated values, so a few files needs an update.
> And we could document what flags makes sense for LVDS etc.

Where would you add that documentation ? The hardest part is to find a
place that will be noticed by developers :-)

I've just submitted a patch that adds a WARN_ON to catch similar issues
in the panel-simple driver. It's not ideal as we really shouldn't have
such code in the kernel, this is something that should be caught as part
of the integration process.

> On the TODO list...
>
> >>> The rest looks good, except the Samsung panel for which I haven't been
> >>> able to locate a datasheet.
> >>> 
> >>> Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>

-- 
Regards,

Laurent Pinchart