From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E6440C54FCB for ; Wed, 22 Apr 2020 20:29:21 +0000 (UTC) Received: from alsa0.perex.cz (alsa0.perex.cz [77.48.224.243]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 5F9512071E for ; Wed, 22 Apr 2020 20:29:21 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alsa-project.org header.i=@alsa-project.org header.b="uc2rj59k" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5F9512071E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=alsa-devel-bounces@alsa-project.org Received: from alsa1.perex.cz (alsa1.perex.cz [207.180.221.201]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by alsa0.perex.cz (Postfix) with ESMTPS id 957D7167E; Wed, 22 Apr 2020 22:28:29 +0200 (CEST) DKIM-Filter: OpenDKIM Filter v2.11.0 alsa0.perex.cz 957D7167E DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=alsa-project.org; s=default; t=1587587359; bh=fY0jnV7niFlIBJIWbBuPnDLzaaDytzFZKCQXuMReZz8=; h=Date:From:To:Subject:In-Reply-To:References:Cc:List-Id: List-Unsubscribe:List-Archive:List-Post:List-Help:List-Subscribe: From; b=uc2rj59kZuwebHHgDq1QDQpNTxH//tROzQreGbLmjKIBiQkUGN8BlNlLDhaRSyAI7 HrZFVxKyarViiw6kKVv7h2i0kRTYABzjUs3KMeoqBEtRazYLy9yvcL3NdKuJBi+PY3 X80V6e7Hs/5cWwb+zadu6ZpwZYOr8rkDKTzdZ6m4= Received: from alsa1.perex.cz (localhost.localdomain [127.0.0.1]) by alsa1.perex.cz (Postfix) with ESMTP id A234CF80142; Wed, 22 Apr 2020 22:28:28 +0200 (CEST) Received: by alsa1.perex.cz (Postfix, from userid 50401) id 07D1BF801D9; Wed, 22 Apr 2020 22:28:19 +0200 (CEST) Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by alsa1.perex.cz (Postfix) with ESMTPS id 5713DF800F2 for ; Wed, 22 Apr 2020 22:28:16 +0200 (CEST) DKIM-Filter: OpenDKIM Filter v2.11.0 alsa1.perex.cz 5713DF800F2 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 53344AEA8; Wed, 22 Apr 2020 20:28:15 +0000 (UTC) Date: Wed, 22 Apr 2020 22:28:15 +0200 Message-ID: From: Takashi Iwai To: Alexander Tsoy Subject: Re: [PATCH] ALSA: usb-audio: Apply async workaround for Scarlett 2i4 2nd gen In-Reply-To: References: <7190177d62f349eea7a5d1056924a63fc4270d43.camel@tsoy.me> <20200422185522.3347-1-grpintar@gmail.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI/1.14.6 (Maruoka) FLIM/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL/10.8 Emacs/25.3 (x86_64-suse-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka") Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Cc: Gregor Pintar , alsa-devel@alsa-project.org X-BeenThere: alsa-devel@alsa-project.org X-Mailman-Version: 2.1.15 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" On Wed, 22 Apr 2020 21:26:23 +0200, Alexander Tsoy wrote: > > В Ср, 22/04/2020 в 20:55 +0200, Gregor Pintar пишет: > > On Wed, 22 Apr 2020 Alexander Tsoy wrote: > > > В Вт, 21/04/2020 в 21:31 +0200, Takashi Iwai пишет: > > > > I wonder, though, whether we can correct the rounding error in > > > > the > > > > driver code, too. > > > > > > I'm not sure if it's possible with currently used Q16.16 > > > arithmetic. > > > > Maybe calculate fixed correction shifts (like it would be feedback)? > > Something like leap year. > > > > In endpoint.c: > > static inline unsigned get_usb_high_speed_rate(unsigned int rate) > > { > > return ((rate << 10) + 62) / 125; > > } > > I guess 62 tries to round it, but exact number is needed. So exact > > value for > > 44100 should be 361267.2. For 48000 it is 360448. > > If only we can deliver that 0.2 by shifting rate somehow? > > > > At least maybe it would be better to disable sample rates that do not > > divide > > by 1000 on SYNC playback endpoints, if there are others sample rates. > > > > But I'm not familar with the code or USB. > > I think instead of accumulating the fractional part of fs/fps in Q16.16 > format we should accumulating remainder of division fs/fps. > > So for 44100 Hz and High Speed USB the calculations would be: > > fs = 44100 > fps = 8000 > rem = 44100 % 8000 = 4100 > accum = 0 > packet_size_min = 44100 / 8000 = 5 > packet_size_max = 44100 + (8000 - 1) / 8000 = 6 > > > 1. accum += rem = 4100 > accum < fps => packet_size = packet_size_min = 5 > > 2. accum += rem = 8200 > accum >= fps => { > packet_size = packet_size_max = 6 > accum -= fps = 200 > } > > 3. accum += rem = 4300 > accum < fps => packet_size = packet_size_min = 5 > > ... > > 80. accum += rem = 8000 > accum >= fps => { > packet_size = packet_size_max = 6 > accum -= fps = 0 > } > ... Yeah, something like that is what I had in my mind. It'd be greatly appreciated if someone can experiment it. Unfortunately I have no proper USB-audio device now at hands... thanks, Takashi