From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nicolin Chen Subject: Re: [PATCH RFC 1/1] ASoC: fsl_ssi: Make fifo watermark and maxburst settings device tree options Date: Fri, 15 Jan 2016 10:38:24 -0800 Message-ID: <20160115183824.GB31703@Asurada-Nvidia> References: <1452788982-11583-1-git-send-email-caleb@crome.org> <20160114201858.GA17567@Asurada-Nvidia> <56984BE7.2050303@tabi.org> <20160115131325.GW6588@sirena.org.uk> <5698F846.5080604@tabi.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Caleb Crome Cc: Timur Tabi , Mark Brown , Xiubo Li , Liam Girdwood , Jaroslav Kysela , Takashi Iwai , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, "alsa-devel@alsa-project.org" List-Id: devicetree@vger.kernel.org On Fri, Jan 15, 2016 at 09:03:28AM -0800, Caleb Crome wrote: > If nobody objects, we can just set the value to 4 and be done with it. I agree. And we may apply it only to i.MX platforms with DMA if other platform owners feel comfortable with the previous settings. > Another question: is the watermark ever going to be different than > maxburst? Is there any reason to have them different? The watermark is merely a threshold to trigger a DMA request. The only relationship with the burst size is that each burst transfer should not carry more data than the number of empty slots; FIFO under/overflow occurs otherwise. So it's just more efficient and safer to set an identical value to both of them. I don't think it will cause functional problems to set TFWM to 4 and burst size to 1 -- It just lets DMA operate in a single data transfer mode.