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From:   Maxime Ripard <maxime@cerno.tech>
To:     Jaroslav Kysela <perex@perex.cz>, Mark Brown <broonie@kernel.org>,
        dri-devel@lists.freedesktop.org,
        Daniel Vetter <daniel.vetter@intel.com>,
        David Airlie <airlied@linux.ie>,
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        Takashi Iwai <tiwai@suse.com>
Cc:     devicetree@vger.kernel.org,
        Dave Stevenson <dave.stevenson@raspberrypi.com>,
        Phil Elwell <phil@raspberrypi.com>,
        Tim Gover <tim.gover@raspberrypi.com>,
        Dom Cobley <dom@raspberrypi.com>, linux-doc@vger.kernel.org,
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        Jonathan Corbet <corbet@lwn.net>,
        Rob Herring <robh+dt@kernel.org>,
        Dom Cobley <popcornmix@gmail.com>
Subject: [PATCH v2 09/12] drm/vc4: hdmi: Remove firmware logic for MAI threshold setting
Date:   Tue, 25 May 2021 15:23:51 +0200
Message-Id: <20210525132354.297468-10-maxime@cerno.tech>
In-Reply-To: <20210525132354.297468-1-maxime@cerno.tech>
References: <20210525132354.297468-1-maxime@cerno.tech>
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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(-)

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 |
-- 
2.31.1