[alsa-devel] [PATCH] ALSA: hda: Modify stream stripe mask only when needed

[Takashi Iwai]

The recent in HD-audio stream management for changing the stripe
control seems causing a regression on some platforms.  The stripe
control is currently used only by HDMI codec, and applying the stripe
mask unconditionally may lead to scratchy and static noises as seen on
some MacBooks.

For addressing the regression, this patch changes the stream
management code to apply the stripe mask conditionally only when the
codec driver requested.

Fixes: 9b6f7e7a296e ("ALSA: hda: program stripe bits for controller")
BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=204477
Cc: <stable at vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai at suse.de>
---
 include/sound/hdaudio.h    |  1 +
 sound/hda/hdac_stream.c    | 19 ++++++++++++-------
 sound/pci/hda/patch_hdmi.c |  5 +++++
 3 files changed, 18 insertions(+), 7 deletions(-)

diff --git a/include/sound/hdaudio.h b/include/sound/hdaudio.h
index b260c5fd2337..e05b95e83d5a 100644
--- a/include/sound/hdaudio.h
+++ b/include/sound/hdaudio.h
@@ -493,6 +493,7 @@ struct hdac_stream {
 	bool prepared:1;
 	bool no_period_wakeup:1;
 	bool locked:1;
+	bool stripe:1;			/* apply stripe control */
 
 	/* timestamp */
 	unsigned long start_wallclk;	/* start + minimum wallclk */
diff --git a/sound/hda/hdac_stream.c b/sound/hda/hdac_stream.c
index d8fe7ff0cd58..f9707fb05efe 100644
--- a/sound/hda/hdac_stream.c
+++ b/sound/hda/hdac_stream.c
@@ -96,12 +96,14 @@ void snd_hdac_stream_start(struct hdac_stream *azx_dev, bool fresh_start)
 			      1 << azx_dev->index,
 			      1 << azx_dev->index);
 	/* set stripe control */
-	if (azx_dev->substream)
-		stripe_ctl = snd_hdac_get_stream_stripe_ctl(bus, azx_dev->substream);
-	else
-		stripe_ctl = 0;
-	snd_hdac_stream_updateb(azx_dev, SD_CTL_3B, SD_CTL_STRIPE_MASK,
-				stripe_ctl);
+	if (azx_dev->stripe) {
+		if (azx_dev->substream)
+			stripe_ctl = snd_hdac_get_stream_stripe_ctl(bus, azx_dev->substream);
+		else
+			stripe_ctl = 0;
+		snd_hdac_stream_updateb(azx_dev, SD_CTL_3B, SD_CTL_STRIPE_MASK,
+					stripe_ctl);
+	}
 	/* set DMA start and interrupt mask */
 	snd_hdac_stream_updateb(azx_dev, SD_CTL,
 				0, SD_CTL_DMA_START | SD_INT_MASK);
@@ -118,7 +120,10 @@ void snd_hdac_stream_clear(struct hdac_stream *azx_dev)
 	snd_hdac_stream_updateb(azx_dev, SD_CTL,
 				SD_CTL_DMA_START | SD_INT_MASK, 0);
 	snd_hdac_stream_writeb(azx_dev, SD_STS, SD_INT_MASK); /* to be sure */
-	snd_hdac_stream_updateb(azx_dev, SD_CTL_3B, SD_CTL_STRIPE_MASK, 0);
+	if (azx_dev->stripe) {
+		snd_hdac_stream_updateb(azx_dev, SD_CTL_3B, SD_CTL_STRIPE_MASK, 0);
+		azx_dev->stripe = 0;
+	}
 	azx_dev->running = false;
 }
 EXPORT_SYMBOL_GPL(snd_hdac_stream_clear);
diff --git a/sound/pci/hda/patch_hdmi.c b/sound/pci/hda/patch_hdmi.c
index 0032bba8cc9d..ed4e98a1057a 100644
--- a/sound/pci/hda/patch_hdmi.c
+++ b/sound/pci/hda/patch_hdmi.c
@@ -32,6 +32,7 @@
 #include <sound/hda_codec.h>
 #include "hda_local.h"
 #include "hda_jack.h"
+#include "hda_controller.h"
 
 static bool static_hdmi_pcm;
 module_param(static_hdmi_pcm, bool, 0644);
@@ -1249,6 +1250,10 @@ static int hdmi_pcm_open(struct hda_pcm_stream *hinfo,
 	per_pin->cvt_nid = per_cvt->cvt_nid;
 	hinfo->nid = per_cvt->cvt_nid;
 
+	/* flip stripe flag for the assigned stream if supported */
+	if (get_wcaps(codec, per_cvt->cvt_nid) & AC_WCAP_STRIPE)
+		azx_stream(get_azx_dev(substream))->stripe = 1;
+
 	snd_hda_set_dev_select(codec, per_pin->pin_nid, per_pin->dev_id);
 	snd_hda_codec_write_cache(codec, per_pin->pin_nid, 0,
 			    AC_VERB_SET_CONNECT_SEL,
-- 
2.16.4