From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sekhar Nori Subject: Re: [PATCH 7/9] ARM: edma: Don't clear EMR of channel in edma_stop Date: Wed, 31 Jul 2013 15:05:24 +0530 Message-ID: <51F8DA5C.9060503@ti.com> References: <1375104595-16018-1-git-send-email-joelf@ti.com> <1375104595-16018-8-git-send-email-joelf@ti.com> <51F77982.7030601@ti.com> <51F89B0B.4080803@ti.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <51F89B0B.4080803-l0cyMroinI0@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: Errors-To: davinci-linux-open-source-bounces+gld-davinci-linux-open-source=gmane.org-VycZQUHpC/PFrsHnngEfi1aTQe2KTcn/@public.gmane.org To: Joel Fernandes Cc: Mark Brown , Tony Lindgren , Grant Likely , Sricharan R , Russell King , Vinod Koul , Lokesh Vutla , Chris Ball , Arnd Bergmann , Rajendra Nayak , Rob Herring , Jason Kridner , Linux OMAP List , Linux ARM Kernel List , Linux DaVinci Kernel List , Balaji TK , Linux MMC List , Linux Kernel Mailing List , Santosh Shilimkar List-Id: linux-mmc@vger.kernel.org On Wednesday 31 July 2013 10:35 AM, Joel Fernandes wrote: > On 07/30/2013 03:29 AM, Sekhar Nori wrote: >> On Monday 29 July 2013 06:59 PM, Joel Fernandes wrote: >>> We certainly don't want error conditions to be cleared anywhere >> >> 'anywhere' is a really loaded term. >> >>> as this will make us 'forget' about missed events. We depend on >>> knowing which events were missed in order to be able to reissue them. >> >>> This fixes a race condition where the EMR was being cleared >>> by the transfer completion interrupt handler. >>> >>> Basically, what was happening was: >>> >>> Missed event >>> | >>> | >>> V >>> SG1-SG2-SG3-Null >>> \ >>> \__TC Interrupt (Almost same time as ARM is executing >>> TC interrupt handler, an event got missed and also forgotten >>> by clearing the EMR). >> >> Sorry, but I dont see how edma_stop() is coming into picture in the race >> you describe? > > In edma_callback function, for the case of DMA_COMPLETE (Transfer > completion interrupt), edma_stop() is called when all sets have been > processed. This had the effect of clearing the EMR. Ah, thanks. I was missing the fact that the race comes into picture only when using the DMA engine driver. I guess that should be mentioned somewhere since it is not immediately obvious. The patch looks good to me. So if you respin just this one with some updated explanation based on what you wrote below, I will take it. Thanks, Sekhar