Hi Aradhya, On Tue, Nov 07, 2023 at 01:17:03AM +0530, Aradhya Bhatia wrote: > Hi Sam, > > Thank you for the suggestion! > > On 06-Nov-23 18:08, Sam Ravnborg wrote: > > Hi Aradhya, > > > > On Tue, Oct 31, 2023 at 12:58:46AM +0530, Aradhya Bhatia wrote: > >> With new connector model, tc358767 will not create the connector, when > >> DRM_BRIDGE_ATTACH_NO_CONNECTOR is set and display-controller driver will > >> rely on format negotiation to setup the encoder format. > >> > >> Add the missing input-format negotiation hook in the > >> drm_bridge_funcs to complete DRM_BRIDGE_ATTACH_NO_CONNECTOR support. > >> > >> Input format is selected to MEDIA_BUS_FMT_RGB888_1X24 as default, as is > >> the case with older model. > >> > >> Reported-by: Jan Kiszka <jan.kiszka@xxxxxxxxxxx> > >> Signed-off-by: Aradhya Bhatia <a-bhatia1@xxxxxx> > >> --- > >> > >> Notes: > >> > >> * Since I do not have hardware with me, this was just build tested. I would > >> appreciate it if someone could test and review it, especically somebody, who > >> uses the bridge for DPI/DSI to eDP format conversion. > >> > >> * The Toshiba TC358767 bridge is not enabled in arm64 defconfig by default, > >> when it should be. Hence, I sent a quick patch[0] earlier. > >> > >> [0]: https://lore.kernel.org/all/20231030152834.18450-1-a-bhatia1@xxxxxx/ > >> > >> drivers/gpu/drm/bridge/tc358767.c | 25 +++++++++++++++++++++++++ > >> 1 file changed, 25 insertions(+) > >> > >> diff --git a/drivers/gpu/drm/bridge/tc358767.c b/drivers/gpu/drm/bridge/tc358767.c > >> index ef2e373606ba..0affcefdeb1c 100644 > >> --- a/drivers/gpu/drm/bridge/tc358767.c > >> +++ b/drivers/gpu/drm/bridge/tc358767.c > >> @@ -1751,6 +1751,30 @@ tc_dpi_atomic_get_input_bus_fmts(struct drm_bridge *bridge, > >> return input_fmts; > >> } > >> > >> +static u32 * > >> +tc_edp_atomic_get_input_bus_fmts(struct drm_bridge *bridge, > >> + struct drm_bridge_state *bridge_state, > >> + struct drm_crtc_state *crtc_state, > >> + struct drm_connector_state *conn_state, > >> + u32 output_fmt, > >> + unsigned int *num_input_fmts) > >> +{ > >> + u32 *input_fmts; > >> + > >> + *num_input_fmts = 0; > >> + > >> + input_fmts = kcalloc(MAX_INPUT_SEL_FORMATS, sizeof(*input_fmts), > >> + GFP_KERNEL); > >> + if (!input_fmts) > >> + return NULL; > >> + > >> + /* This is the DSI/DPI-end bus format */ > >> + input_fmts[0] = MEDIA_BUS_FMT_RGB888_1X24; > >> + *num_input_fmts = 1; > >> + > >> + return input_fmts; > >> +} > > > > You could benefit from using the helper: > > drm_atomic_helper_bridge_propagate_bus_fmt() > > You are right! > > Upon taking a second look, I realize that the bridge chain works with > MEDIA_BUS_FMT_FIXED bus format, when tc358767 is being used in DPI/DSI > to eDP mode (because the panel-bridge does not have a get_output_bus_fmt > hook, and uses the same helper for its get_input_bus_fmt hook). My patch > creates a deviation from that, by forcing MEDIA_BUS_FMT_RGB888_1X24 even > when eDP is involved. > > Using the helper here, will certainly address this deviation. > > However, for the DPI/DSI to DP mode, MEDIA_BUS_FMT_RGB888_1X24 bus > format is required, and *just* using the helper as its get_input_bus_fmt > hook, might not be enough. > > Since tc358767 is the last bridge in DPI/DSI to DP mode, the > output_fmt parameter get defaulted to MEDIA_BUS_FMT_FIXED too, as there > is no get_output_bus_fmt hook present in the driver. If we simply us > the helper here, the input_fmt will also get set to MEDIA_BUS_FMT_FIXED. > This too is an unwanted deviation. > > It seems like the right way to address both the cases, would be by > adding the get_output_bus_fmt hook that sets output_fmt to > MEDIA_BUS_FMT_RGB888_1X24, as well as using the helper as the > get_input_bus_fmt hook. > > If this seems good to you too, I will send a new version of Tomi's > series[0] which incorporates this patch. I never managed to fully wrap my head around the bus fmt negotiation, and as I am trying to recover from a flu this is not the time to try. Your explanations sounds like you have grasped it so I suggest to move ahead. Sam
