Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752110AbcLFFqV (ORCPT ); Tue, 6 Dec 2016 00:46:21 -0500 Received: from relay1.mentorg.com ([192.94.38.131]:57653 "EHLO relay1.mentorg.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751932AbcLFFqT (ORCPT ); Tue, 6 Dec 2016 00:46:19 -0500 From: Jiada Wang To: , , , CC: , , , Subject: [PATCH v2 1/2] ALSA: usb-audio: more tolerant packetsize Date: Tue, 6 Dec 2016 14:46:14 +0900 Message-ID: <20161206054615.29187-2-jiada_wang@mentor.com> X-Mailer: git-send-email 2.9.3 In-Reply-To: <20161206054615.29187-1-jiada_wang@mentor.com> References: <20161206054615.29187-1-jiada_wang@mentor.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1479 Lines: 35 From: Andreas Pape 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 Signed-off-by: Jiada Wang --- 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