From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joel Fernandes Subject: [PATCH 4/9] dma: edma: Find missed events and issue them Date: Mon, 29 Jul 2013 08:29:50 -0500 Message-ID: <1375104595-16018-5-git-send-email-joelf@ti.com> References: <1375104595-16018-1-git-send-email-joelf@ti.com> Mime-Version: 1.0 Content-Type: text/plain Return-path: In-Reply-To: <1375104595-16018-1-git-send-email-joelf@ti.com> Sender: linux-kernel-owner@vger.kernel.org To: Tony Lindgren , Sekhar Nori , Santosh Shilimkar , Sricharan R , Rajendra Nayak , Lokesh Vutla , Matt Porter , Grant Likely , Rob Herring , Vinod Koul , Dan Williams , Mark Brown , Benoit Cousson , Russell King , Arnd Bergmann , Olof Johansson , Balaji TK , Gururaja Hebbar , Chris Ball , Jason Kridner Cc: Linux OMAP List , Linux ARM Kernel List , Linux DaVinci Kernel List , Linux Kernel Mailing List , Linux MMC List , Joel Fernandes List-Id: linux-omap@vger.kernel.org In an effort to move to using Scatter gather lists of any size with EDMA as discussed at [1] instead of placing limitations on the driver, we work through the limitations of the EDMAC hardware to find missed events and issue them. The sequence of events that require this are: For the scenario where MAX slots for an EDMA channel is 3: SG1 -> SG2 -> SG3 -> SG4 -> SG5 -> SG6 -> Null The above SG list will have to be DMA'd in 2 sets: (1) SG1 -> SG2 -> SG3 -> Null (2) SG4 -> SG5 -> SG6 -> Null After (1) is succesfully transferred, the events from the MMC controller donot stop coming and are missed by the time we have setup the transfer for (2). So here, we catch the events missed as an error condition and issue them manually. [1] http://marc.info/?l=linux-omap&m=137416733628831&w=2 Signed-off-by: Joel Fernandes --- drivers/dma/edma.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/drivers/dma/edma.c b/drivers/dma/edma.c index d9a151b..aa4989f 100644 --- a/drivers/dma/edma.c +++ b/drivers/dma/edma.c @@ -417,7 +417,15 @@ static void edma_callback(unsigned ch_num, u16 ch_status, void *data) break; case DMA_CC_ERROR: - dev_dbg(dev, "transfer error on channel %d\n", ch_num); + if (echan->edesc) { + dev_dbg(dev, "Missed event on %d, retrying\n", + ch_num); + edma_clean_channel(echan->ch_num); + edma_stop(echan->ch_num); + edma_start(echan->ch_num); + edma_manual_trigger(echan->ch_num); + } + dev_dbg(dev, "handled error on channel %d\n", ch_num); break; default: break; -- 1.7.9.5