From patchwork Fri Nov 6 11:11:35 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sjoerd Simons X-Patchwork-Id: 7568251 Return-Path: X-Original-To: patchwork-linux-samsung-soc@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 62AF09F9BC for ; Fri, 6 Nov 2015 11:11:45 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 7466C206D8 for ; Fri, 6 Nov 2015 11:11:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 13C8E206DE for ; Fri, 6 Nov 2015 11:11:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161067AbbKFLLm (ORCPT ); Fri, 6 Nov 2015 06:11:42 -0500 Received: from bhuna.collabora.co.uk ([93.93.135.160]:43228 "EHLO bhuna.collabora.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1031997AbbKFLLl (ORCPT ); Fri, 6 Nov 2015 06:11:41 -0500 Received: from [127.0.0.1] (localhost [127.0.0.1]) (Authenticated sender: sjoerd) with ESMTPSA id 04931601159 Received: by dusk.luon.net (Postfix, from userid 1000) id C01A023248; Fri, 6 Nov 2015 12:11:35 +0100 (CET) From: Sjoerd Simons To: Vinod Koul Cc: linux-samsung-soc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-rockchip@lists.infradead.org, Krzysztof Kozlowski , dmaengine@vger.kernel.org, linux-arm-kernel@vger.kernel.org Subject: [PATCH] dmaengine: pl330: Fix race in residue reporting Date: Fri, 6 Nov 2015 12:11:35 +0100 Message-Id: <1446808295-23149-1-git-send-email-sjoerd.simons@collabora.co.uk> X-Mailer: git-send-email 2.6.2 Sender: linux-samsung-soc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-samsung-soc@vger.kernel.org X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, T_RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP When a transfer completes there is a small window between the descriptor being unset as the current active one in the thread and it being marked as done. This causes the residue to be incorrectly set when pl330_tx_status is run in that window. Practically this caused issue for me with audio playback as the residue goes up during a transfer (as the in-progress transfer is no longer accounted for), which makes the higher levels think the audio ringbuffer wrapped around and thus did a sudden big jump forward. To resolve this, add a field protected by the dma engine lock to indicate the transfer is done but the status hasn't been updated yet. Also fix the locking in pl330_tx_status, as the function inspects the threads req_running field and queries the dma engine for the current state of the running transfer the dma engine lock needs to be held to ensure the active descriptor doesn't change underneath it. Signed-off-by: Sjoerd Simons --- drivers/dma/pl330.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c index 17ee758..6c8243b 100644 --- a/drivers/dma/pl330.c +++ b/drivers/dma/pl330.c @@ -503,6 +503,8 @@ struct dma_pl330_desc { struct pl330_reqcfg rqcfg; enum desc_status status; + /* Transfer completed, but not yet moved to DONE state */ + bool xferred; int bytes_requested; bool last; @@ -1463,6 +1465,9 @@ static void dma_pl330_rqcb(struct dma_pl330_desc *desc, enum pl330_op_err err) spin_lock_irqsave(&pch->lock, flags); desc->status = DONE; + spin_lock(&pch->thread->dmac->lock); + desc->xferred = false; + spin_unlock(&pch->thread->dmac->lock); spin_unlock_irqrestore(&pch->lock, flags); @@ -1595,6 +1600,7 @@ static int pl330_update(struct pl330_dmac *pl330) /* Detach the req */ descdone = thrd->req[active].desc; + descdone->xferred = true; thrd->req[active].desc = NULL; thrd->req_running = -1; @@ -2250,13 +2256,14 @@ pl330_tx_status(struct dma_chan *chan, dma_cookie_t cookie, goto out; spin_lock_irqsave(&pch->lock, flags); + spin_lock(&pch->thread->dmac->lock); if (pch->thread->req_running != -1) running = pch->thread->req[pch->thread->req_running].desc; /* Check in pending list */ list_for_each_entry(desc, &pch->work_list, node) { - if (desc->status == DONE) + if (desc->xferred || desc->status == DONE) transferred = desc->bytes_requested; else if (running && desc == running) transferred = @@ -2281,6 +2288,7 @@ pl330_tx_status(struct dma_chan *chan, dma_cookie_t cookie, if (desc->last) residual = 0; } + spin_unlock(&pch->thread->dmac->lock); spin_unlock_irqrestore(&pch->lock, flags); out: