From patchwork Tue Oct 30 10:39:38 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Timo Wischer X-Patchwork-Id: 10660657 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id B353B1751 for ; Tue, 30 Oct 2018 10:40:08 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 9D5E029F2A for ; Tue, 30 Oct 2018 10:40:08 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 9161429FA5; Tue, 30 Oct 2018 10:40:08 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_NONE autolearn=ham version=3.3.1 Received: from alsa0.perex.cz (alsa0.perex.cz [77.48.224.243]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 5A4D029F2A for ; Tue, 30 Oct 2018 10:40:07 +0000 (UTC) Received: from alsa0.perex.cz (localhost [127.0.0.1]) by alsa0.perex.cz (Postfix) with ESMTP id 35A5D2677D0; Tue, 30 Oct 2018 11:40:05 +0100 (CET) X-Original-To: alsa-devel@alsa-project.org Delivered-To: alsa-devel@alsa-project.org Received: by alsa0.perex.cz (Postfix, from userid 1000) id 990CA2677D0; Tue, 30 Oct 2018 11:40:02 +0100 (CET) Received: from smtp1.de.adit-jv.com (smtp1.de.adit-jv.com [62.225.105.245]) by alsa0.perex.cz (Postfix) with ESMTP id 3C2EE267692; Tue, 30 Oct 2018 11:39:57 +0100 (CET) Received: from localhost (smtp1.de.adit-jv.com [127.0.0.1]) by smtp1.de.adit-jv.com (Postfix) with ESMTP id 5E1543C013A; Tue, 30 Oct 2018 11:39:56 +0100 (CET) Received: from smtp1.de.adit-jv.com ([127.0.0.1]) by localhost (smtp1.de.adit-jv.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id TBLmjBNx9iqO; Tue, 30 Oct 2018 11:39:49 +0100 (CET) Received: from HI2EXCH01.adit-jv.com (hi2exch01.adit-jv.com [10.72.92.24]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-SHA384 (256/256 bits)) (No client certificate requested) by smtp1.de.adit-jv.com (Postfix) with ESMTPS id CDBC63C0034; Tue, 30 Oct 2018 11:39:49 +0100 (CET) Received: from vmlxhi-087.adit-jv.com (10.72.93.172) by HI2EXCH01.adit-jv.com (10.72.92.24) with Microsoft SMTP Server (TLS) id 14.3.408.0; Tue, 30 Oct 2018 11:39:49 +0100 From: To: , Date: Tue, 30 Oct 2018 11:39:38 +0100 Message-ID: <1540895978-21601-1-git-send-email-twischer@de.adit-jv.com> X-Mailer: git-send-email 2.7.4 MIME-Version: 1.0 X-Originating-IP: [10.72.93.172] Cc: Laxmi Devi , alsa-devel@alsa-project.org Subject: [alsa-devel] [PATCH - dmix v2 1/1] pcm: dmix: Align slave_hw_ptr to slave period boundary X-BeenThere: alsa-devel@alsa-project.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: "Alsa-devel mailing list for ALSA developers - http://www.alsa-project.org" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: alsa-devel-bounces@alsa-project.org Sender: alsa-devel-bounces@alsa-project.org X-Virus-Scanned: ClamAV using ClamSMTP From: Laxmi Devi These changes are required due to the kernel commit 07b7acb51d283d8469696c906b91f1882696a4d4 ("ASoC: rsnd: update pointer more accurate") Issue is that snd_pcm_wait() goes back to waiting because the hw_ptr is not period aligned. Therefore snd_pcm_wait() will block for a longer time as required. With these rcar driver changes the exact position of the dma is returned. During snd_pcm_start they read hw_ptr as reference, and this hw_ptr is now not period aligned, and is a little ahead over the period while it is read. Therefore when the avail is calculated during snd_pcm_wait(), it is missing the avail_min by a few frames. Consider the below example: Considering the application is trying to write 0x120 frames and the period_size = 0x60, avail_min = 0x120 and buffersize = 0x360 : rsnd_pointer=0x12c -> dma pointer at the end of second write during snd_pcm_dmix_start(). Since another 0x120 buffer is available, application writes 0x120 and goes to snd_pcm_wait(). It is woken up after 3 snd_pcm_period_elapsed() to see rsnd_pointer=0x248. So hw_ptr = new_slave_hw_ptr - reference_slave_hw_ptr = 0x248 - 0x12c = 0x11c. It needs 4 more frames to be able to write. And so it goes back to waiting. But since 3 snd_pcm_period_elapsed(), 3 periods should be available and it should have been able to write. If rsnd_pointer during the start was 0x120 which is 3 periods then 0x248 - 0x120 = 128 it could go on with write. Signed-off-by: Laxmi Devi --- > On 10/29/18 16:54, Takashi Iwai wrote: > The problem is that aligning the start essentially imposes an > artificial long latency, and changes the behavior out of sudden. Now, we are only align the salve_hw_ptr which also solves our delay issue. But this change should not increase the latency because the write position is given by slave_appl_ptr. Do you see any other drawbacks? Best regards Timo diff --git a/src/pcm/pcm_dmix.c b/src/pcm/pcm_dmix.c index a6a8f3a..eaa0b0f 100644 --- a/src/pcm/pcm_dmix.c +++ b/src/pcm/pcm_dmix.c @@ -560,6 +560,8 @@ static int snd_pcm_dmix_hwsync(snd_pcm_t *pcm) static void reset_slave_ptr(snd_pcm_t *pcm, snd_pcm_direct_t *dmix) { dmix->slave_appl_ptr = dmix->slave_hw_ptr = *dmix->spcm->hw.ptr; + dmix->slave_hw_ptr = ((dmix->slave_hw_ptr / dmix->slave_period_size) + * dmix->slave_period_size); if (pcm->buffer_size > pcm->period_size * 2) return; /* If we have too litte periods, better to align the start position