A kind reminder that this patch fixes HDMI audio on all v1 platforms. The (now already merged[1]) driver for MT2701/MT7623N also depends on it, as mentioned in the cover letter of that series[2].
[1]: https://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound.git/commit/?id=4d9c6bbfed7d9a3224a66f3d135cdef21a430168 [2]: https://lore.kernel.org/all/[email protected]/ On Wed, Apr 15, 2026 at 04:04:08PM +0100, Daniel Golle wrote: > The CLK_MM_HDMI_AUDIO and CLK_MM_HDMI_SPDIF mmsys gates feed the > HDMI TX internal audio measurement block which derives CTS values > for the ACR packets embedded in the TMDS stream. These clocks are > enabled once at driver probe time and then left untouched across > bridge atomic_enable / atomic_disable cycles. > > On every observed stale-state event -- a blank/unblank cycle, or > a cold boot with the monitor off followed by a later hotplug -- > the measurement block remains armed against the previous state > and fails to latch a valid CTS on the subsequent bridge enable. > Video recovers cleanly but the audio data islands never regain > lock and the HDMI sink sees no audio, even though the ASoC stack, > the AFE, and the HDMI TX audio packetizer are all programmed > correctly. > > Debugging the issue of audio no longer working after vblank it was > found that an unbind+bind of the mediatek-drm-hdmi platform driver > recovers audio in all such scenarios without disturbing video. > The only audio-relevant side effect of that rebind is an off->on edge > on CLK_MM_HDMI_AUDIO / CLK_MM_HDMI_SPDIF via the probe path. Pulsing > those two clocks directly at the end of mtk_hdmi_bridge_atomic_enable > reproduces that recovery on every enable and doesn't hurt on the > first enable after boot. > > Fixes: 8f83f26891e1 ("drm/mediatek: Add HDMI support") > Signed-off-by: Daniel Golle <[email protected]> > --- > drivers/gpu/drm/mediatek/mtk_hdmi.c | 16 ++++++++++++++++ > 1 file changed, 16 insertions(+) > > diff --git a/drivers/gpu/drm/mediatek/mtk_hdmi.c > b/drivers/gpu/drm/mediatek/mtk_hdmi.c > index 1ea2598547800..9050d7785f109 100644 > --- a/drivers/gpu/drm/mediatek/mtk_hdmi.c > +++ b/drivers/gpu/drm/mediatek/mtk_hdmi.c > @@ -1065,6 +1065,22 @@ static void mtk_hdmi_bridge_atomic_enable(struct > drm_bridge *bridge, > phy_power_on(hdmi->phy); > mtk_hdmi_send_infoframe(hdmi, &hdmi->mode); > > + /* > + * Pulse the HDMI TX audio clocks off/on on every bridge enable. > + * The CLK_MM_HDMI_AUDIO and CLK_MM_HDMI_SPDIF mmsys gates feed > + * the HDMI TX internal audio measurement block that derives CTS > + * for the ACR packets embedded in the TMDS stream. Without an > + * off->on edge at bridge enable the block can stay armed against > + * stale state from a previous enable (e.g. after blank/unblank, > + * or after a monitor that was off at boot is plugged in later) > + * and fails to latch a valid CTS, leaving the audio path silent > + * even though video recovers. The pulse is what an unbind+bind > + * of the HDMI platform driver effectively does, and it recovers > + * audio in all observed stale-state scenarios. > + */ > + mtk_hdmi_clk_disable_audio(hdmi); > + mtk_hdmi_clk_enable_audio(hdmi); > + > hdmi->enabled = true; > } > > -- > 2.53.0 >
