From patchwork Sun Aug 7 19:01:48 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Robert Jarzmik X-Patchwork-Id: 9266535 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 0711760754 for ; Sun, 7 Aug 2016 19:04:07 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id EA139275A2 for ; Sun, 7 Aug 2016 19:04:06 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id DEDD727D16; Sun, 7 Aug 2016 19:04:06 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.2 required=2.0 tests=BAYES_00,FREEMAIL_FROM, RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.9]) (using TLSv1.2 with cipher AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 969A8275A2 for ; Sun, 7 Aug 2016 19:04:06 +0000 (UTC) Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.85_2 #1 (Red Hat Linux)) id 1bWTLN-00069R-FW; Sun, 07 Aug 2016 19:02:41 +0000 Received: from smtp04.smtpout.orange.fr ([80.12.242.126] helo=smtp.smtpout.orange.fr) by bombadil.infradead.org with esmtps (Exim 4.85_2 #1 (Red Hat Linux)) id 1bWTL3-0005wz-DP for linux-arm-kernel@lists.infradead.org; Sun, 07 Aug 2016 19:02:22 +0000 Received: from belgarion.home ([109.220.218.149]) by mwinf5d27 with ME id UK1u1t00h3DzaaM03K1uzw; Sun, 07 Aug 2016 21:01:57 +0200 X-ME-Helo: belgarion.home X-ME-Date: Sun, 07 Aug 2016 21:01:57 +0200 X-ME-IP: 109.220.218.149 From: Robert Jarzmik To: Daniel Mack , Haojian Zhuang , Robert Jarzmik , Vinod Koul Subject: [PATCH] dmaengine: pxa_dma: fix hotchain corner case Date: Sun, 7 Aug 2016 21:01:48 +0200 Message-Id: <1470596509-1726-1-git-send-email-robert.jarzmik@free.fr> X-Mailer: git-send-email 2.1.4 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20160807_120221_818920_B0A5824C X-CRM114-Status: GOOD ( 12.92 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Virus-Scanned: ClamAV using ClamSMTP In the case where a descriptor is chained on a running channel, and as explained in the comment in the code 10 lines above, the success of the chaining is ensured either if : - the DMA is still running - or if the chained transfer is completed Unfortunately the transfer completness test was done on the descriptor to which the transfer was chained, and not the transfer being chained at the end, ie. hot-chained. This corner case is extremely hard to trigger, as usually the DMA chain is still running, and the first case takes care of returning success of the hot-chaining. It was seen by hot-chaining several "small transfers" to a running "big transfer", not in a real-life usecase but by testing the robustness of the driver. Signed-off-by: Robert Jarzmik --- drivers/dma/pxa_dma.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/dma/pxa_dma.c b/drivers/dma/pxa_dma.c index e756a30ccba2..64758daa9eee 100644 --- a/drivers/dma/pxa_dma.c +++ b/drivers/dma/pxa_dma.c @@ -635,7 +635,7 @@ static bool pxad_try_hotchain(struct virt_dma_chan *vc, vd_last_issued = list_entry(vc->desc_issued.prev, struct virt_dma_desc, node); pxad_desc_chain(vd_last_issued, vd); - if (is_chan_running(chan) || is_desc_completed(vd_last_issued)) + if (is_chan_running(chan) || is_desc_completed(vd)) return true; }