Re: [PATCH v4 1/3] drm/panel: Add RGB666 variant of Innolux AT070TN90

Maxime Ripard
2018-05-09T07:12:26Z

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On Tue, May 08, 2018 at 12:04:11AM +0200, Paul Kocialkowski wrote:
> This adds timings for the RGB666 variant of the Innolux AT070TN90 panel,
> as found on the Ainol AW1 tablet.
>
> The panel also supports RGB888 output. When RGB666 mode is used instead,
> the two extra lanes per component are grounded.
>
> In the future, it might become necessary to introduce a dedicated
> device-tree property to specify the bus format to use instead of the
> default one for the panel. This will allow supporting different bus
> formats for the same panel modes.
>
> Signed-off-by: Paul Kocialkowski <contact-W9ppeneeCTY@public.gmane.org>
> ---
> drivers/gpu/drm/panel/panel-simple.c | 26 ++++++++++++++++++++++++++
> 1 file changed, 26 insertions(+)
>
> diff --git a/drivers/gpu/drm/panel/panel-simple.c b/drivers/gpu/drm/panel/panel-simple.c
> index cbf1ab404ee7..32e30d5a8f08 100644
> --- a/drivers/gpu/drm/panel/panel-simple.c
> +++ b/drivers/gpu/drm/panel/panel-simple.c
> @@ -1063,6 +1063,29 @@ static const struct panel_desc innolux_at043tn24 = {
> .bus_flags = DRM_BUS_FLAG_DE_HIGH | DRM_BUS_FLAG_PIXDATA_POSEDGE,
> };
>
> +static const struct drm_display_mode innolux_at070tn90_mode = {
> + .clock = 40000,
> + .hdisplay = 800,
> + .hsync_start = 800 + 112,
> + .hsync_end = 800 + 112 + 1,
> + .htotal = 800 + 112 + 1 + 87,
> + .vdisplay = 480,
> + .vsync_start = 480 + 141,
> + .vsync_end = 480 + 141 + 1,
> + .vtotal = 480 + 141 + 1 + 38,
> + .vrefresh = 60,
> +};
> +
> +static const struct panel_desc innolux_at070tn90 = {
> + .modes = &innolux_at070tn90_mode,
> + .num_modes = 1,
> + .size = {
> + .width = 154,
> + .height = 86,
> + },
> + .bus_format = MEDIA_BUS_FMT_RGB666_1X18,
> +};
> +

I'm not really convinced this is the right approach. You said it
yourself, the panel is using a 24-bits interface, and you just happen
to have a tablet that routed it using a 18-bits interface instead.

That doesn't belong in the driver, especially associated to the
compatible, but where the routing is described: in the device
tree. And given that the panel interface is a 24 bits panel, if we
were to have a default, we should have this one, and not the one
fitting your use case.

Maxime

--
Maxime Ripard, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering