Hi Tomi,
On 12-May-23 14:45, Tomi Valkeinen wrote:
> On 09/05/2023 12:30, Aradhya Bhatia wrote:
>> From: Nikhil Devshatwar <nikhil.nd@xxxxxx>
>>
>> With new connector model, mhdp bridge will not create the connector and
>> SoC driver will rely on format negotiation to setup the encoder format.
>>
>> Support minimal format negotiations hooks in the drm_bridge_funcs.
>> Complete format negotiation can be added based on EDID data.
>> This patch adds the minimal required support to avoid failure
>> after moving to new connector model.
>>
>> Signed-off-by: Nikhil Devshatwar <nikhil.nd@xxxxxx>
>> Reviewed-by: Tomi Valkeinen <tomi.valkeinen@xxxxxx>
>
> You need to add your SoB to this and the other patches.
Okay!
>
>> ---
>>
>> Notes:
>>
>> changes from v1:
>> * cosmetic fixes, commit message update.
>>
>> changes from v5:
>> * dropped the default_bus_format variable and directly assigned
>> MEDIA_BUS_FMT_RGB121212_1X36 to input_fmts.
>>
>> .../drm/bridge/cadence/cdns-mhdp8546-core.c | 25 +++++++++++++++++++
>> 1 file changed, 25 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
>> b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
>> index f6822dfa3805..623e4235c94f 100644
>> --- a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
>> +++ b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
>> @@ -2146,6 +2146,30 @@ cdns_mhdp_bridge_atomic_reset(struct drm_bridge
>> *bridge)
>> return &cdns_mhdp_state->base;
>> }
>> +static u32 *cdns_mhdp_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;
>> +
>> + if (output_fmt != MEDIA_BUS_FMT_FIXED)
>> + return NULL;
>
> The tfp410 and sii902x drivers don't have the above check. Why does mhdp
> need it? Or the other way, why don't tfp410 and sii902x need it?
I had removed this condition in order to follow status quo, from the
ITE-66121 HDMI bridge driver.
The idea would have been to drop this for MHDP as well, but I guess I
overlooked this one.
However...
> I guess at the moment we always do get MEDIA_BUS_FMT_FIXED as the out
> fmt (in all three bridge drivers), don't we?
... I tested again to ensure that the above is indeed the case. And
ended up catching some odd behavior.
It turns out that for all the HDMI bridges (TFP410, SII902X, ITE-66121),
the format negotiation doesn't stop at output_fmt = MEDIA_BUS_FMT_FIXED.
The {bridge}_get_input_format API gets called again with the output_fmt
= MEDIA_BUS_FMT_RGB24_1X24.
This doesn't happen with the MHDP driver. Format negotiation with MHDP
bridge stops after one round, at output_fmt = MEDIA_BUS_FMT_FIXED.
Regards
Aradhya
