From: Laurent Pinchart [mailto:laurent.pinchart@xxxxxxxxxxxxxxxx] Sent: Thursday, February 3, 2022 12:46 AM > > Hi Christoph, > Hi Laurent, > On Tue, Feb 01, 2022 at 12:07:17PM +0100, Christoph Niedermaier wrote: >> Without the data-mapping devicetree property my display won't >> work properly. It is flickering, because the bus flags won't >> be assigned without a defined bus format by the imx parallel >> display driver. There was a discussion about the removal [1] >> and an agreement that a better solution is needed, but it is >> missing so far. So what would be the better approach? >> >> [1] https://patchwork.freedesktop.org/patch/357659/?series=74705&rev=1 >> >> This reverts commit d021d751c14752a0266865700f6f212fab40a18c. >> >> Signed-off-by: Christoph Niedermaier <cniedermaier@xxxxxxxxxxxxxxxxxx> >> Cc: Marek Vasut <marex@xxxxxxx> >> Cc: Sam Ravnborg <sam@xxxxxxxxxxxx> >> Cc: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx> >> Cc: Maxime Ripard <mripard@xxxxxxxxxx> >> Cc: Philipp Zabel <p.zabel@xxxxxxxxxxxxxx> >> Cc: David Airlie <airlied@xxxxxxxx> >> Cc: Daniel Vetter <daniel@xxxxxxxx> >> Cc: Shawn Guo <shawnguo@xxxxxxxxxx> >> Cc: Sascha Hauer <s.hauer@xxxxxxxxxxxxxx> >> Cc: Pengutronix Kernel Team <kernel@xxxxxxxxxxxxxx> >> Cc: Fabio Estevam <festevam@xxxxxxxxx> >> Cc: NXP Linux Team <linux-imx@xxxxxxx> >> Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx >> To: dri-devel@xxxxxxxxxxxxxxxxxxxxx >> --- >> drivers/gpu/drm/panel/panel-simple.c | 11 +++++++++++ >> 1 file changed, 11 insertions(+) >> >> diff --git a/drivers/gpu/drm/panel/panel-simple.c b/drivers/gpu/drm/panel/panel-simple.c >> index 3c08f9827acf..2c683d94a3f3 100644 >> --- a/drivers/gpu/drm/panel/panel-simple.c >> +++ b/drivers/gpu/drm/panel/panel-simple.c >> @@ -453,6 +453,7 @@ static int panel_dpi_probe(struct device *dev, >> struct panel_desc *desc; >> unsigned int bus_flags; >> struct videomode vm; >> + const char *mapping; >> int ret; >> >> np = dev->of_node; >> @@ -477,6 +478,16 @@ static int panel_dpi_probe(struct device *dev, >> of_property_read_u32(np, "width-mm", &desc->size.width); >> of_property_read_u32(np, "height-mm", &desc->size.height); >> >> + of_property_read_string(np, "data-mapping", &mapping); >> + if (!strcmp(mapping, "rgb24")) >> + desc->bus_format = MEDIA_BUS_FMT_RGB888_1X24; >> + else if (!strcmp(mapping, "rgb565")) >> + desc->bus_format = MEDIA_BUS_FMT_RGB565_1X16; >> + else if (!strcmp(mapping, "bgr666")) >> + desc->bus_format = MEDIA_BUS_FMT_RGB666_1X18; >> + else if (!strcmp(mapping, "lvds666")) >> + desc->bus_format = MEDIA_BUS_FMT_RGB666_1X24_CPADHI; > > You're right that there's an issue, but a revert isn't the right option. > The commit you're reverting never made it in a stable release, because > it was deemed to not be a good enough option. > > First of all, any attempt to fix this should include an update to the DT > binding. Second, as this is about DPI panels, the LVDS option should be > dropped. Finally, I've shared some initial thoughts in [1], maybe you > can reply to that e-mail to continue the discussion there ? According to your thoughts in [1] you mean that the bus format should be build out of the devicetree properties bus-width and data-shift. It would be possible for evenly structured busses like RGB888_1X24 and RGB666_1X18, but what about a bus like RGB565_1X16, where each color has different bus width. Also the order of the colors should be defined to differ between busses like RGB888_1X24 and GBR888_1X24. Are there any ideas how can this be covered? > > [1] https://lore.kernel.org/all/20200303185531.GJ11333@xxxxxxxxxxxxxxxxxxxxxxxxxx/ > >> + >> /* Extract bus_flags from display_timing */ >> bus_flags = 0; >> vm.flags = timing->flags; > Regards Christoph
