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From: Jiada Wang <jiada_wang@mentor.com>
To: <perex@perex.cz>, <tiwai@suse.com>, <o-takashi@sakamocchi.jp>,
	<clemens@ladisch.de>
Cc: <alsa-devel@alsa-project.org>, <linux-kernel@vger.kernel.org>,
	<jiada_wang@mentor.com>, <apape@de.adit-jv.com>
Subject: [PATCH v2 1/2] ALSA: usb-audio: more tolerant packetsize
Date: Tue, 6 Dec 2016 14:46:14 +0900	[thread overview]
Message-ID: <20161206054615.29187-2-jiada_wang@mentor.com> (raw)
In-Reply-To: <20161206054615.29187-1-jiada_wang@mentor.com>

From: Andreas Pape <apape@de.adit-jv.com>

since commit 57e6dae1087b ("ALSA: usb-audio: do not trust too-big
wMaxPacketSize values"), the expected packetsize is always limited
to nominal + 25%. It was discovered, that some devices have a much
higher jitter in used packetsizes than 25% which would result in BABBLE
condition and dropping of packets.
A better solution is so assume the jitter to be the nominal packetsize:
-one nearly empty packet followed by a almost 150% sized one.

V2: changed to assume max frequency is +50 of nominal packetsize.

Signed-off-by: Andreas Pape <apape@de.adit-jv.com>
Signed-off-by: Jiada Wang <jiada_wang@mentor.com>
---
 sound/usb/endpoint.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c
index c470251..a2931f4 100644
--- a/sound/usb/endpoint.c
+++ b/sound/usb/endpoint.c
@@ -632,8 +632,8 @@ static int data_ep_set_params(struct snd_usb_endpoint *ep,
 	ep->stride = frame_bits >> 3;
 	ep->silence_value = pcm_format == SNDRV_PCM_FORMAT_U8 ? 0x80 : 0;
 
-	/* assume max. frequency is 25% higher than nominal */
-	ep->freqmax = ep->freqn + (ep->freqn >> 2);
+	/* assume max. frequency is 50% higher than nominal */
+	ep->freqmax = ep->freqn + (ep->freqn >> 1);
 	/* Round up freqmax to nearest integer in order to calculate maximum
 	 * packet size, which must represent a whole number of frames.
 	 * This is accomplished by adding 0x0.ffff before converting the
-- 
2.9.3

WARNING: multiple messages have this Message-ID (diff)
From: Jiada Wang <jiada_wang@mentor.com>
To: perex@perex.cz, tiwai@suse.com, o-takashi@sakamocchi.jp,
	clemens@ladisch.de
Cc: alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org,
	jiada_wang@mentor.com, apape@de.adit-jv.com
Subject: [PATCH v2 1/2] ALSA: usb-audio: more tolerant packetsize
Date: Tue, 6 Dec 2016 14:46:14 +0900	[thread overview]
Message-ID: <20161206054615.29187-2-jiada_wang@mentor.com> (raw)
In-Reply-To: <20161206054615.29187-1-jiada_wang@mentor.com>

From: Andreas Pape <apape@de.adit-jv.com>

since commit 57e6dae1087b ("ALSA: usb-audio: do not trust too-big
wMaxPacketSize values"), the expected packetsize is always limited
to nominal + 25%. It was discovered, that some devices have a much
higher jitter in used packetsizes than 25% which would result in BABBLE
condition and dropping of packets.
A better solution is so assume the jitter to be the nominal packetsize:
-one nearly empty packet followed by a almost 150% sized one.

V2: changed to assume max frequency is +50 of nominal packetsize.

Signed-off-by: Andreas Pape <apape@de.adit-jv.com>
Signed-off-by: Jiada Wang <jiada_wang@mentor.com>
---
 sound/usb/endpoint.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c
index c470251..a2931f4 100644
--- a/sound/usb/endpoint.c
+++ b/sound/usb/endpoint.c
@@ -632,8 +632,8 @@ static int data_ep_set_params(struct snd_usb_endpoint *ep,
 	ep->stride = frame_bits >> 3;
 	ep->silence_value = pcm_format == SNDRV_PCM_FORMAT_U8 ? 0x80 : 0;
 
-	/* assume max. frequency is 25% higher than nominal */
-	ep->freqmax = ep->freqn + (ep->freqn >> 2);
+	/* assume max. frequency is 50% higher than nominal */
+	ep->freqmax = ep->freqn + (ep->freqn >> 1);
 	/* Round up freqmax to nearest integer in order to calculate maximum
 	 * packet size, which must represent a whole number of frames.
 	 * This is accomplished by adding 0x0.ffff before converting the
-- 
2.9.3

  reply	other threads:[~2016-12-06  5:46 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-12-06  5:46 [PATCH 0/2 v2] usb-audio misc fix Jiada Wang
2016-12-06  5:46 ` Jiada Wang
2016-12-06  5:46 ` Jiada Wang [this message]
2016-12-06  5:46   ` [PATCH v2 1/2] ALSA: usb-audio: more tolerant packetsize Jiada Wang
2016-12-06  7:13   ` Takashi Iwai
2016-12-06  7:13     ` Takashi Iwai
2016-12-06 12:11   ` [alsa-devel] " Clemens Ladisch
2016-12-06  5:46 ` [PATCH 2/2] ALSA: usb-audio: avoid setting of sample rate multiple times on bus Jiada Wang
2016-12-06  5:46   ` Jiada Wang
2016-12-06 15:02 ` [PATCH 0/2 v2] usb-audio misc fix Takashi Iwai
2016-12-06 15:02   ` Takashi Iwai

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