From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934485AbbEMOjx (ORCPT ); Wed, 13 May 2015 10:39:53 -0400 Received: from mailgw02.mediatek.com ([210.61.82.184]:41633 "EHLO mailgw02.mediatek.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S964898AbbEMOjw (ORCPT ); Wed, 13 May 2015 10:39:52 -0400 X-Listener-Flag: 11101 From: Koro Chen To: , , , CC: , , , , , , Koro Chen Subject: [RFC PATCH] ALSA: pcm: Modify double acknowledged interrupts check condition Date: Wed, 13 May 2015 22:39:03 +0800 Message-ID: <1431527943-64178-1-git-send-email-koro.chen@mediatek.com> X-Mailer: git-send-email 1.8.1.1.dirty MIME-Version: 1.0 Content-Type: text/plain X-MTK: N Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Currently in snd_pcm_update_hw_ptr0 during interrupt, we consider there were double acknowledged interrupts when: 1. HW reported pointer is smaller than expected, and 2. Time from last update time (hdelta) is over half a buffer time. However, when HW reported pointer is only a few bytes smaller than expected, and when hdelta is just a little larger than half a buffer time (e.g. ping-pong buffer), it wrongly treats this IRQ as double acknowledged. The condition #2 uses jiffies, but jiffies is not high resolution since it is integer. We should consider jiffies inaccuracy. Signed-off-by: Koro Chen --- sound/core/pcm_lib.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c index ac6b33f..7d45645 100644 --- a/sound/core/pcm_lib.c +++ b/sound/core/pcm_lib.c @@ -339,7 +339,7 @@ static int snd_pcm_update_hw_ptr0(struct snd_pcm_substream *substream, if (delta > new_hw_ptr) { /* check for double acknowledged interrupts */ hdelta = curr_jiffies - runtime->hw_ptr_jiffies; - if (hdelta > runtime->hw_ptr_buffer_jiffies/2) { + if (hdelta > runtime->hw_ptr_buffer_jiffies/2 + 1) { hw_base += runtime->buffer_size; if (hw_base >= runtime->boundary) { hw_base = 0; -- 1.8.1.1.dirty