Re: [PATCH] drm/amd/display: Restore analog connector support

["Timur Kristóf" <timur.kristof@gmail.com>]

Hi,

Tested this on the following:
HD 7870 XT - works
R9 280X (Tahiti) - works
R9 380X (Tonga) - works
A10-7850K (Kaveri) - broken

It seems that some other chunks of code were removed which were necessary for 
external DP bridge encoders to work properly. Those will need to be added back 
too, otherwise we regress Kaveri APUs.

Best regards,
Timur


On Thursday, April 16, 2026 7:38:39 PM Central European Summer Time Timur 
Kristóf wrote:
> Hi,
> 
> I'll test this on a few different old GPUs and get back to you.
> 
> Thanks,
> Timur
> 
> Alex Hung <alex.hung@amd.com> ezt írta (időpont: 2026. ápr. 16., Csü 17:46):
> > Reviewed-by: Alex Hung <alex.hung@amd.com>
> > 
> > On 4/15/26 16:41, Roman.Li@amd.com wrote:
> > > From: Roman Li <Roman.Li@amd.com>
> > > 
> > > [Why]
> > > The analog connector support was accidentally removed,
> > > causing a crash when connecting an analog monitor.
> > > 
> > > [How]
> > > This patch restores the functions and pointers required for proper
> > > analog
> > > and DP bridge encoder support on legacy GPUs.
> > > 
> > > Fixes: 66715fc0ecfd ("drm/amd/display: Sync dcn42 with DC 3.2.373")
> > > Cc: Timur Kristóf <timur.kristof@gmail.com>
> > > Signed-off-by: Roman Li <Roman.Li@amd.com>
> > > ---
> > > 
> > >   .../amd/display/dc/hwss/dce110/dce110_hwseq.c | 53 +++++++++++++++++++
> > >   1 file changed, 53 insertions(+)
> > > 
> > > diff --git a/drivers/gpu/drm/amd/display/dc/hwss/dce110/dce110_hwseq.c
> > 
> > b/drivers/gpu/drm/amd/display/dc/hwss/dce110/dce110_hwseq.c
> > 
> > > index 5273ca09fe12..e76abc877f4a 100644
> > > --- a/drivers/gpu/drm/amd/display/dc/hwss/dce110/dce110_hwseq.c
> > > +++ b/drivers/gpu/drm/amd/display/dc/hwss/dce110/dce110_hwseq.c
> > > @@ -677,6 +677,48 @@ dce110_dac_encoder_control(struct pipe_ctx
> > 
> > *pipe_ctx, bool enable)
> > 
> > >       bios->funcs->encoder_control(bios, &encoder_control);
> > >   
> > >   }
> > > 
> > > +static void
> > > +dce110_external_encoder_control(enum bp_external_encoder_control_action
> > 
> > action,
> > 
> > > +                             struct dc_link *link,
> > > +                             struct dc_crtc_timing *timing)
> > > +{
> > > +     struct dc *dc = link->ctx->dc;
> > > +     struct dc_bios *bios = link->ctx->dc_bios;
> > > +     const struct dc_link_settings *link_settings =
> > 
> > &link->cur_link_settings;
> > 
> > > +     enum bp_result bp_result = BP_RESULT_OK;
> > > +     struct bp_external_encoder_control ext_cntl = {
> > > +             .action = action,
> > > +             .connector_obj_id = link->link_enc->connector,
> > > +             .encoder_id = link->ext_enc_id,
> > > +             .lanes_number = link_settings->lane_count,
> > > +             .link_rate = link_settings->link_rate,
> > > +
> > > +             /* Use signal type of the real link encoder, ie. DP */
> > > +             .signal = link->connector_signal,
> > > +
> > > +             /* We don't know the timing yet when executing the SETUP
> > 
> > action,
> > 
> > > +              * so use a reasonably high default value. It seems that
> > 
> > ENABLE
> > 
> > > +              * can change the actual pixel clock but doesn't work with
> > 
> > higher
> > 
> > > +              * pixel clocks than what SETUP was called with.
> > > +              */
> > 
> > > +             .pixel_clock = timing ? timing->pix_clk_100hz / 10 :
> > 300000,
> > 
> > > +             .color_depth = timing ? timing->display_color_depth :
> > COLOR_DEPTH_888,
> > 
> > > +     };
> > > +     DC_LOGGER_INIT(dc->ctx);
> > > +
> > > +     bp_result = bios->funcs->external_encoder_control(bios,
> > > &ext_cntl);
> > > +
> > > +     if (bp_result != BP_RESULT_OK)
> > 
> > > +             DC_LOG_ERROR("Failed to execute external encoder action:
> > 0x%x\n", action);
> > 
> > > +}
> > > +
> > > +static void
> > > +dce110_prepare_ddc(struct dc_link *link)
> > > +{
> > > +     if (link->ext_enc_id.id)
> > > +
> >  
> >  dce110_external_encoder_control(EXTERNAL_ENCODER_CONTROL_DDC_SETUP, link,
> > 
> > NULL);
> > 
> > > +}
> > > +
> > > 
> > >   static bool
> > >   dce110_dac_load_detect(struct dc_link *link)
> > >   {
> > > 
> > > @@ -3376,6 +3418,15 @@ void dce110_enable_tmds_link_output(struct
> > 
> > dc_link *link,
> > 
> > >       link->phy_state.symclk_state = SYMCLK_ON_TX_ON;
> > >   
> > >   }
> > > 
> > > +static void dce110_enable_analog_link_output(
> > > +             struct dc_link *link,
> > > +             uint32_t pix_clk_100hz)
> > > +{
> > > +     link->link_enc->funcs->enable_analog_output(
> > > +                     link->link_enc,
> > > +                     pix_clk_100hz);
> > > +}
> > > +
> > > 
> > >   void dce110_enable_dp_link_output(
> > >   
> > >               struct dc_link *link,
> > >               const struct link_resource *link_res,
> > > 
> > > @@ -3513,8 +3564,10 @@ static const struct hw_sequencer_funcs
> > 
> > dce110_funcs = {
> > 
> > >       .enable_lvds_link_output = dce110_enable_lvds_link_output,
> > >       .enable_tmds_link_output = dce110_enable_tmds_link_output,
> > >       .enable_dp_link_output = dce110_enable_dp_link_output,
> > > 
> > > +     .enable_analog_link_output = dce110_enable_analog_link_output,
> > > 
> > >       .disable_link_output = dce110_disable_link_output,
> > >       .dac_load_detect = dce110_dac_load_detect,
> > > 
> > > +     .prepare_ddc = dce110_prepare_ddc,
> > > 
> > >   };
> > >   
> > >   static const struct hwseq_private_funcs dce110_private_funcs = {