From mboxrd@z Thu Jan 1 00:00:00 1970 From: Liam Girdwood Subject: Re: [RFC 3/4] OMAP3: McBSP: Add interface for transmit FIFO state query Date: Tue, 02 Mar 2010 13:58:04 +0000 Message-ID: <1267538284.3201.15.camel@odin> References: <1267537191-25254-1-git-send-email-peter.ujfalusi@nokia.com> <1267537191-25254-4-git-send-email-peter.ujfalusi@nokia.com> <1267537920.24345.7.camel@eenurkka-desktop> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail-fx0-f220.google.com (mail-fx0-f220.google.com [209.85.220.220]) by alsa0.perex.cz (Postfix) with ESMTP id 2FFE11038E3 for ; Tue, 2 Mar 2010 14:58:06 +0100 (CET) Received: by fxm20 with SMTP id 20so722453fxm.32 for ; Tue, 02 Mar 2010 05:58:05 -0800 (PST) In-Reply-To: <1267537920.24345.7.camel@eenurkka-desktop> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: alsa-devel-bounces@alsa-project.org Errors-To: alsa-devel-bounces@alsa-project.org To: ext-eero.nurkkala@nokia.com Cc: "tiwai@suse.de" , "alsa-devel@alsa-project.org" , "broonie@opensource.wolfsonmicro.com" , "Ujfalusi Peter (Nokia-D/Tampere)" List-Id: alsa-devel@alsa-project.org On Tue, 2010-03-02 at 15:52 +0200, Eero Nurkkala wrote: > On Tue, 2010-03-02 at 14:39 +0100, Ujfalusi Peter (Nokia-D/Tampere) > wrote: > > New function for reading the XBUFFSTAT register, which holds > > the fill state of the transmit buffer on McBSP. > > > > Signed-off-by: Peter Ujfalusi > > --- > > Reading the XBUFFSTAT register is by no means accurate. > IIRC, it reports the buffer status incorrectly about 1/50 times > on average (@ 48000khz); with simple math, it may be read during the DMA > burst. Or is it guaranteed not being read during DMA transfer / have > you otherwise verified the behavior? I agree, I've also seen XBUFFSTAT giving complete garbage with mcbsp3. Liam -- Freelance Developer, SlimLogic Ltd ASoC and Voltage Regulator Maintainer. http://www.slimlogic.co.uk