Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754708Ab3HEQSv (ORCPT ); Mon, 5 Aug 2013 12:18:51 -0400 Received: from arroyo.ext.ti.com ([192.94.94.40]:39240 "EHLO arroyo.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754465Ab3HEQP5 (ORCPT ); Mon, 5 Aug 2013 12:15:57 -0400 From: Joel Fernandes 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 Subject: [PATCH v3 02/12] ARM: edma: Don't clear EMR of channel in edma_stop Date: Mon, 5 Aug 2013 11:14:47 -0500 Message-ID: <1375719297-12871-3-git-send-email-joelf@ti.com> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1375719297-12871-1-git-send-email-joelf@ti.com> References: <1375719297-12871-1-git-send-email-joelf@ti.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2267 Lines: 63 We certainly don't want error conditions to be cleared any other place but the EDMA error handler, as this will make us 'forget' about missed events we might need to know errors have occurred. 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). This causes the following problems: 1. If error interrupt is also pending and TC interrupt clears the EMR by calling edma_stop as has been observed in the edma_callback function, the ARM will execute the error interrupt even though the EMR is clear. As a result, the dma_ccerr_handler returns IRQ_NONE. If this happens enough number of times, IRQ subsystem disables the interrupt thinking its spurious which makes error handler never execute again. 2. Also even if error handler doesn't return IRQ_NONE, the removing of EMR removes the knowledge about which channel had a missed event, and thus a manual trigger on such channels cannot be performed. The EMR is ultimately being cleared by the Error interrupt handler once it is handled so we remove code that does it in edma_stop and allow it to happen there. Signed-off-by: Joel Fernandes --- arch/arm/common/edma.c | 1 - 1 file changed, 1 deletion(-) diff --git a/arch/arm/common/edma.c b/arch/arm/common/edma.c index 3567ba1..6433b6c 100644 --- a/arch/arm/common/edma.c +++ b/arch/arm/common/edma.c @@ -1307,7 +1307,6 @@ void edma_stop(unsigned channel) edma_shadow0_write_array(ctlr, SH_EECR, j, mask); edma_shadow0_write_array(ctlr, SH_ECR, j, mask); edma_shadow0_write_array(ctlr, SH_SECR, j, mask); - edma_write_array(ctlr, EDMA_EMCR, j, mask); pr_debug("EDMA: EER%d %08x\n", j, edma_shadow0_read_array(ctlr, SH_EER, j)); -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/