[PATCH] drm/amd/display: Fix DP audio DTO1 clock source on DCE 6.

[Alex Deucher]

Applied.  Thanks!

Alex

On Fri, Aug 8, 2025 at 2:39 AM Rodrigo Siqueira <siqueira at igalia.com> wrote:
>
> On 08/02, Timur Kristóf wrote:
> > On DCE 6, DP audio was not working. However, it worked when an
> > HDMI monitor was also plugged in.
> >
> > Looking at dce_aud_wall_dto_setup it seems that the main
> > difference is that we use DTO1 when only DP is plugged in.
> >
> > When programming DTO1, it uses audio_dto_source_clock_in_khz
> > which is set from get_dp_ref_freq_khz
> >
> > The dce60_get_dp_ref_freq_khz implementation looks incorrect,
> > because DENTIST_DISPCLK_CNTL seems to be always zero on DCE 6,
> > so it isn't usable.
> > I compared dce60_get_dp_ref_freq_khz to the legacy display code,
> > specifically dce_v6_0_audio_set_dto, and it turns out that in
> > case of DCE 6, it needs to use the display clock. With that,
> > DP audio started working on Pitcairn, Oland and Cape Verde.
> >
> > However, it still didn't work on Tahiti. Despite having the
> > same DCE version, Tahiti seems to have a different audio device.
> > After some trial and error I realized that it works with the
> > default display clock as reported by the VBIOS, not the current
> > display clock.
> >
> > The patch was tested on all four SI GPUs:
> >
> > * Pitcairn (DCE 6.0)
> > * Oland (DCE 6.4)
> > * Cape Verde (DCE 6.0)
> > * Tahiti (DCE 6.0 but different)
> >
> > The testing was done on Samsung Odyssey G7 LS28BG700EPXEN on
> > each of the above GPUs, at the following settings:
> >
> > * 4K 60 Hz
> > * 1080p 60 Hz
> > * 1080p 144 Hz
> >
> > Signed-off-by: Timur Kristóf <timur.kristof at gmail.com>
> > ---
> >  .../display/dc/clk_mgr/dce60/dce60_clk_mgr.c  | 21 ++++++-------------
> >  1 file changed, 6 insertions(+), 15 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/amd/display/dc/clk_mgr/dce60/dce60_clk_mgr.c b/drivers/gpu/drm/amd/display/dc/clk_mgr/dce60/dce60_clk_mgr.c
> > index 0267644717b2..883591706db9 100644
> > --- a/drivers/gpu/drm/amd/display/dc/clk_mgr/dce60/dce60_clk_mgr.c
> > +++ b/drivers/gpu/drm/amd/display/dc/clk_mgr/dce60/dce60_clk_mgr.c
> > @@ -83,22 +83,13 @@ static const struct state_dependent_clocks dce60_max_clks_by_state[] = {
> >  static int dce60_get_dp_ref_freq_khz(struct clk_mgr *clk_mgr_base)
> >  {
> >       struct clk_mgr_internal *clk_mgr = TO_CLK_MGR_INTERNAL(clk_mgr_base);
> > -     int dprefclk_wdivider;
> > -     int dp_ref_clk_khz;
> > -     int target_div;
> > +     struct dc_context *ctx = clk_mgr_base->ctx;
> > +     int dp_ref_clk_khz = 0;
> >
> > -     /* DCE6 has no DPREFCLK_CNTL to read DP Reference Clock source */
> > -
> > -     /* Read the mmDENTIST_DISPCLK_CNTL to get the currently
> > -      * programmed DID DENTIST_DPREFCLK_WDIVIDER*/
> > -     REG_GET(DENTIST_DISPCLK_CNTL, DENTIST_DPREFCLK_WDIVIDER, &dprefclk_wdivider);
> > -
> > -     /* Convert DENTIST_DPREFCLK_WDIVIDERto actual divider*/
> > -     target_div = dentist_get_divider_from_did(dprefclk_wdivider);
> > -
> > -     /* Calculate the current DFS clock, in kHz.*/
> > -     dp_ref_clk_khz = (DENTIST_DIVIDER_RANGE_SCALE_FACTOR
> > -             * clk_mgr->base.dentist_vco_freq_khz) / target_div;
> > +     if (ASIC_REV_IS_TAHITI_P(ctx->asic_id.hw_internal_rev))
> > +             dp_ref_clk_khz = ctx->dc_bios->fw_info.default_display_engine_pll_frequency;
> > +     else
> > +             dp_ref_clk_khz = clk_mgr_base->clks.dispclk_khz;
> >
> >       return dce_adjust_dp_ref_freq_for_ss(clk_mgr, dp_ref_clk_khz);
> >  }
> > --
> > 2.50.1
> >
>
> Very nice patch! I checked the mentioned functions, and it looks correct
> to me.
>
> I added other display folks for further review/validation. It could be a
> good idea to include this patch in the next week's promotion.
>
> Reviewed-by: Rodrigo Siqueira <siqueira at igalia.com>
>
> Thanks
>
> --
> Rodrigo Siqueira