[PATCH] drm/amd/display: restore edid reading from a given i2c adapter

[Alex Hung]

On 2/10/25 15:18, Mario Limonciello wrote:
> On 2/9/2025 16:50, Melissa Wen wrote:
>> When switching to drm_edid, we slightly changed how to get edid by
>> removing the possibility of getting them from dc_link when in aux
>> transaction mode. As MST doesn't initialize the connector with
>> `drm_connector_init_with_ddc()`, restore the original behavior to avoid
>> functional changes.
>>
>> Fixes: 48edb2a4256e ("drm/amd/display: switch amdgpu_dm_connector to 
>> use struct drm_edid")
>> Signed-off-by: Melissa Wen <mwen at igalia.com>
>> ---
>>
>>
>> Hi,
>>
>> So far, there is no reports about an issue related to this but I noticed
>> this potential functional change when investigating the previous
>> freesync problem. I'm not 100% clear if MST takes this path without
>> initializating connector->ddc, but I propose here to restore the
>> original behavior to avoid regressions.
>>
>> Melissa
> 
> I think this looks reasonable.
> 
> Charlie,
> 
> Can this get included in this week's promotion tests?

I just shared this patch to this week's promoter, Roman, and this patch 
will be included in promotion test.

> 
> Thanks,
> 
>>
>>
>>   .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c   | 17 +++++++++++++++--
>>   1 file changed, 15 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/ 
>> drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>> index a8421c07b160..0cd22a6686a3 100644
>> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>> @@ -7269,8 +7269,14 @@ static void 
>> amdgpu_dm_connector_funcs_force(struct drm_connector *connector)
>>       struct dc_link *dc_link = aconnector->dc_link;
>>       struct dc_sink *dc_em_sink = aconnector->dc_em_sink;
>>       const struct drm_edid *drm_edid;
>> +    struct i2c_adapter *ddc;
>> -    drm_edid = drm_edid_read(connector);
>> +    if (dc_link->aux_mode)
>> +        ddc = &aconnector->dm_dp_aux.aux.ddc;
>> +    else
>> +        ddc = &aconnector->i2c->base;
>> +
>> +    drm_edid = drm_edid_read_ddc(connector, ddc);
>>       drm_edid_connector_update(connector, drm_edid);
>>       if (!drm_edid) {
>>           DRM_ERROR("No EDID found on connector: %s.\n", connector- 
>> >name);
>> @@ -7315,14 +7321,21 @@ static int get_modes(struct drm_connector 
>> *connector)
>>   static void create_eml_sink(struct amdgpu_dm_connector *aconnector)
>>   {
>>       struct drm_connector *connector = &aconnector->base;
>> +    struct dc_link *dc_link = aconnector->dc_link;
>>       struct dc_sink_init_data init_params = {
>>               .link = aconnector->dc_link,
>>               .sink_signal = SIGNAL_TYPE_VIRTUAL
>>       };
>>       const struct drm_edid *drm_edid;
>>       const struct edid *edid;
>> +    struct i2c_adapter *ddc;
>> -    drm_edid = drm_edid_read(connector);
>> +    if (dc_link->aux_mode)
>> +        ddc = &aconnector->dm_dp_aux.aux.ddc;
>> +    else
>> +        ddc = &aconnector->i2c->base;
>> +
>> +    drm_edid = drm_edid_read_ddc(connector, ddc);
>>       drm_edid_connector_update(connector, drm_edid);
>>       if (!drm_edid) {
>>           DRM_ERROR("No EDID found on connector: %s.\n", connector- 
>> >name);
>