diff mbox series

[v2,09/12] drm/vc4: hdmi: Remove firmware logic for MAI threshold setting

Message ID 20210525132354.297468-10-maxime@cerno.tech (mailing list archive)
State New, archived
Headers show
Series drm/vc4: hdmi: Enable Channel Mapping, IEC958, HBR Passthrough using hdmi-codec | expand

Commit Message

Maxime Ripard May 25, 2021, 1:23 p.m. UTC 
From: Dom Cobley <popcornmix@gmail.com>

This was a workaround for bugs in hardware on earlier Pi models
and wasn't totally successful.

It makes audio quality worse on a Pi4 at the higher sample rates

Signed-off-by: Dom Cobley <popcornmix@gmail.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
---
 drivers/gpu/drm/vc4/vc4_hdmi.c | 22 ++++++----------------
 1 file changed, 6 insertions(+), 16 deletions(-)

Comments

Nicolas Saenz Julienne June 1, 2021, 8:52 a.m. UTC | #1 
On Tue, 2021-05-25 at 15:23 +0200, Maxime Ripard wrote:
> From: Dom Cobley <popcornmix@gmail.com>
> 
> This was a workaround for bugs in hardware on earlier Pi models
> and wasn't totally successful.

What's to expect sound wise on older RPis?

Regards,
Nicolas
Dom Cobley June 1, 2021, 10:01 a.m. UTC | #2 
On Tue, 1 Jun 2021 at 09:52, nicolas saenz julienne <nsaenz@kernel.org>
wrote:

> What's to expect sound wise on older RPis?


I'd say 8 channel 48kHz is good. 2 channel 192KHz is good.
Higher than that and we start to lose samples in the HDMI MAI bus fifo.

The firmware workaround made 4 channel 192kHz somewhat more reliable, but
it would still fail when sdram was busy,
so I don't think it's worth maintaining that.
diff mbox series

Patch

diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
index 0cf9949a749f..b7e3bd89e237 100644
--- a/drivers/gpu/drm/vc4/vc4_hdmi.c
+++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
@@ -1269,22 +1269,12 @@  static int vc4_hdmi_audio_hw_params(struct snd_pcm_substream *substream,
 	audio_packet_config |= VC4_SET_FIELD(channel_mask,
 					     VC4_HDMI_AUDIO_PACKET_CEA_MASK);
 
-	/* Set the MAI threshold.  This logic mimics the firmware's. */
-	if (vc4_hdmi->audio.samplerate > 96000) {
-		HDMI_WRITE(HDMI_MAI_THR,
-			   VC4_SET_FIELD(0x12, VC4_HD_MAI_THR_DREQHIGH) |
-			   VC4_SET_FIELD(0x12, VC4_HD_MAI_THR_DREQLOW));
-	} else if (vc4_hdmi->audio.samplerate > 48000) {
-		HDMI_WRITE(HDMI_MAI_THR,
-			   VC4_SET_FIELD(0x14, VC4_HD_MAI_THR_DREQHIGH) |
-			   VC4_SET_FIELD(0x12, VC4_HD_MAI_THR_DREQLOW));
-	} else {
-		HDMI_WRITE(HDMI_MAI_THR,
-			   VC4_SET_FIELD(0x10, VC4_HD_MAI_THR_PANICHIGH) |
-			   VC4_SET_FIELD(0x10, VC4_HD_MAI_THR_PANICLOW) |
-			   VC4_SET_FIELD(0x10, VC4_HD_MAI_THR_DREQHIGH) |
-			   VC4_SET_FIELD(0x10, VC4_HD_MAI_THR_DREQLOW));
-	}
+	/* Set the MAI threshold */
+	HDMI_WRITE(HDMI_MAI_THR,
+		   VC4_SET_FIELD(0x10, VC4_HD_MAI_THR_PANICHIGH) |
+		   VC4_SET_FIELD(0x10, VC4_HD_MAI_THR_PANICLOW) |
+		   VC4_SET_FIELD(0x10, VC4_HD_MAI_THR_DREQHIGH) |
+		   VC4_SET_FIELD(0x10, VC4_HD_MAI_THR_DREQLOW));
 
 	HDMI_WRITE(HDMI_MAI_CONFIG,
 		   VC4_HDMI_MAI_CONFIG_BIT_REVERSE |