On Tue, 27 Oct 2020 11:15:58 +0100, Maxime Ripard wrote: > > When running the trigger hook, ALSA by default will take a spinlock, and > thus will run the trigger hook in atomic context. > > However, our HDMI driver will send the infoframes as part of the trigger > hook, and part of that process is to wait for a bit to be cleared for up to > 100ms. To be nicer to the system, that wait has some usleep_range that > interact poorly with the atomic context. > > There's several ways we can fix this, but the more obvious one is to make > ALSA take a mutex instead by setting the nonatomic flag on the DAI link. > That doesn't work though, since now the cyclic callback installed by the > dmaengine helpers in ALSA will take a mutex, while that callback is run by > dmaengine's virt-chan code in a tasklet where sleeping is not allowed > either. > > Given the delay we need to poll the bit for, changing the usleep_range for > a udelay and keep running it from a context where interrupts are disabled > is not really a good option either. > > However, we can move the infoframe setup code in the hw_params hook, like > is usually done in other HDMI controllers, that isn't protected by a > spinlock and thus where we can sleep. Infoframes will be sent on a regular > basis anyway, and since hw_params is where the audio parameters that end up > in the infoframes are setup, this also makes a bit more sense. > > Fixes: bb7d78568814 ("drm/vc4: Add HDMI audio support") > Suggested-by: Mark Brown <broonie@xxxxxxxxxx> > Signed-off-by: Maxime Ripard <maxime@xxxxxxxxxx> Reviewed-by: Takashi Iwai <tiwai@xxxxxxx> thanks, Takashi > --- > drivers/gpu/drm/vc4/vc4_hdmi.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c > index 74da7c00ecd0..ec3ba3ecd32a 100644 > --- a/drivers/gpu/drm/vc4/vc4_hdmi.c > +++ b/drivers/gpu/drm/vc4/vc4_hdmi.c > @@ -1077,6 +1077,7 @@ static int vc4_hdmi_audio_hw_params(struct snd_pcm_substream *substream, > struct snd_soc_dai *dai) > { > struct vc4_hdmi *vc4_hdmi = dai_to_hdmi(dai); > + struct drm_encoder *encoder = &vc4_hdmi->encoder.base.base; > struct device *dev = &vc4_hdmi->pdev->dev; > u32 audio_packet_config, channel_mask; > u32 channel_map; > @@ -1136,6 +1137,8 @@ static int vc4_hdmi_audio_hw_params(struct snd_pcm_substream *substream, > HDMI_WRITE(HDMI_AUDIO_PACKET_CONFIG, audio_packet_config); > vc4_hdmi_set_n_cts(vc4_hdmi); > > + vc4_hdmi_set_audio_infoframe(encoder); > + > return 0; > } > > @@ -1143,11 +1146,9 @@ static int vc4_hdmi_audio_trigger(struct snd_pcm_substream *substream, int cmd, > struct snd_soc_dai *dai) > { > struct vc4_hdmi *vc4_hdmi = dai_to_hdmi(dai); > - struct drm_encoder *encoder = &vc4_hdmi->encoder.base.base; > > switch (cmd) { > case SNDRV_PCM_TRIGGER_START: > - vc4_hdmi_set_audio_infoframe(encoder); > vc4_hdmi->audio.streaming = true; > > if (vc4_hdmi->variant->phy_rng_enable) > -- > 2.26.2 >