From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C25AEC43381 for ; Wed, 27 Mar 2019 18:25:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9528521738 for ; Wed, 27 Mar 2019 18:25:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1553711126; bh=ETUIxRvNr4obvfqXpnvcNfxLTG9vINn7D3DWO1ixhdk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=orN/dQ/NDTWNpVnU+e/LrVZK4GlYpxI6dqTEC7HmHMo0DWCcJrf4aGsTK6Lv2An52 mhUnJVk9R+2ogJQRfXtDOlpagz8ZCxk93eHcDLU4G4VUJ3CDQd9S7k759xyDAe6DsJ vGV/uq8745iM8BFHuBRErBD5C/wHJ7zjv/LtbEk8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404182AbfC0SZZ (ORCPT ); Wed, 27 Mar 2019 14:25:25 -0400 Received: from mail.kernel.org ([198.145.29.99]:44326 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2391320AbfC0SZR (ORCPT ); Wed, 27 Mar 2019 14:25:17 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id BACCF21871; Wed, 27 Mar 2019 18:25:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1553711116; bh=ETUIxRvNr4obvfqXpnvcNfxLTG9vINn7D3DWO1ixhdk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=StQTLJob/6QfHsJ17t71F5APGVDrHy7G38JWAed0jSnu4E9MKjS/aULoOkFhOl1QI rw0NhPyUby618sLHO3hJudPTXd2ftdLIzrlXUPZvzQCpeohRt7foD7M1f/XUN7OnJG l0aSPf6UFqCJ0+ZzsQgDdHBjZTPw07Fs3hDxjYM0= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Ben Dooks , Vinod Koul , Sasha Levin , dmaengine@vger.kernel.org, linux-tegra@vger.kernel.org Subject: [PATCH AUTOSEL 4.4 62/63] dmaengine: tegra: avoid overflow of byte tracking Date: Wed, 27 Mar 2019 14:23:22 -0400 Message-Id: <20190327182323.18577-62-sashal@kernel.org> X-Mailer: git-send-email 2.19.1 In-Reply-To: <20190327182323.18577-1-sashal@kernel.org> References: <20190327182323.18577-1-sashal@kernel.org> MIME-Version: 1.0 X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Ben Dooks [ Upstream commit e486df39305864604b7e25f2a95d51039517ac57 ] The dma_desc->bytes_transferred counter tracks the number of bytes moved by the DMA channel. This is then used to calculate the information passed back in the in the tegra_dma_tx_status callback, which is usually fine. When the DMA channel is configured as continous, then the bytes_transferred counter will increase over time and eventually overflow to become negative so the residue count will become invalid and the ALSA sound-dma code will report invalid hardware pointer values to the application. This results in some users becoming confused about the playout position and putting audio data in the wrong place. To fix this issue, always ensure the bytes_transferred field is modulo the size of the request. We only do this for the case of the cyclic transfer done ISR as anyone attempting to move 2GiB of DMA data in one transfer is unlikely. Note, we don't fix the issue that we should /never/ transfer a negative number of bytes so we could make those fields unsigned. Reviewed-by: Dmitry Osipenko Signed-off-by: Ben Dooks Acked-by: Jon Hunter Signed-off-by: Vinod Koul Signed-off-by: Sasha Levin --- drivers/dma/tegra20-apb-dma.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/drivers/dma/tegra20-apb-dma.c b/drivers/dma/tegra20-apb-dma.c index c8f79dcaaee8..67f201b8dcda 100644 --- a/drivers/dma/tegra20-apb-dma.c +++ b/drivers/dma/tegra20-apb-dma.c @@ -632,7 +632,10 @@ static void handle_cont_sngl_cycle_dma_done(struct tegra_dma_channel *tdc, sgreq = list_first_entry(&tdc->pending_sg_req, typeof(*sgreq), node); dma_desc = sgreq->dma_desc; - dma_desc->bytes_transferred += sgreq->req_len; + /* if we dma for long enough the transfer count will wrap */ + dma_desc->bytes_transferred = + (dma_desc->bytes_transferred + sgreq->req_len) % + dma_desc->bytes_requested; /* Callback need to be call */ if (!dma_desc->cb_count) -- 2.19.1