From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dong Aisheng Subject: Re: [alsa-devel] [PATCH v2 2/3] ASoC: dmaengine-pcm: Rename and deprecate snd_dmaengine_pcm_pointer Date: Wed, 20 Jun 2012 21:41:32 +0800 Message-ID: <20120620134131.GK10387@shlinux2.ap.freescale.net> References: <1339438302-12417-1-git-send-email-lars@metafoo.de> <1339438302-12417-2-git-send-email-lars@metafoo.de> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Return-path: Content-Disposition: inline In-Reply-To: <1339438302-12417-2-git-send-email-lars@metafoo.de> Sender: linux-kernel-owner@vger.kernel.org To: Lars-Peter Clausen Cc: Mark Brown , Liam Girdwood , Vinod Koul , Ola Lilja , alsa-devel@alsa-project.org, Russell King , Mika Westerberg , linux-kernel@vger.kernel.org, Shawn Guo List-Id: alsa-devel@alsa-project.org On Mon, Jun 11, 2012 at 08:11:41PM +0200, Lars-Peter Clausen wrote: > Currently the sound dmaengine pcm helper functions implement the pcm_pointer > callback by trying to count the number of elapsed periods. This is done by > advancing the stream position in the dmaengine callback by one period. > Unfortunately there is no guarantee that the callback will be called for each > elapsed period. It may be possible that under high system load it is only called > once for multiple elapsed periods. This patch renames the current implementation > and documents its shortcomings and that it should not be used anymore in new > drivers. > > The next patch will introduce a new snd_dmaengine_pcm_pointer which will be > implemented based on querying the current stream position from the dma device. > > Signed-off-by: Lars-Peter Clausen > Acked-by: Dong Aisheng > --- > If you are maintaining a pcm driver which use the dmaengine pcm helper please > check if you platform works with the new snd_dmaengine_pcm_pointer > implementation which is added in the next patch (ux500 seems to be good > candidate). And if it does send a follow-up patch to convert your platform to > the new implementation. If it does not please try to fix or add residue > reporting support to your dmaengine driver. > Will try it after adding cyclic tx_status support for mxs/imx dma driver. Regards Dong Aisheng