From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AIpwx4/lam9+8zapblxkAEd/M63o/4iMT/uws+xdYbaUfRUKhsPHbI4Qp5foyoB/72MMi1k+qZEM ARC-Seal: i=1; a=rsa-sha256; t=1524405600; cv=none; d=google.com; s=arc-20160816; b=JqCBwUiETuOz3ZBSJ82tOn6Inx9cJE76KyoBs3s/YSp42NdUJahQzQeHR2Q+KqsgLF PrI/LriQscs34r/12NRSQ6vk6w3wgEYqFmwqYl/8KxKlBKvH0F2chu5QOpu9k5TVWvo+ 6yITeZn1xX1LP2ktGkabzwNbaVN2L+0p/rKfAxxOEBZCXW1uvguN18jBgzYBymP8KC3q 9mY81rE4QNyG1JMHgS1tBMdx1z2zyzRd5v4/Ff/doAqNBe/WbYoOQGtEXhRcCP6c3RPc hU4CZwbwf16631WQYZx4xmazWip2I+6Qvu8W5BTwNi4IJxCCUB0uafD99wVeGRzeJrIb kPpA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=mime-version:user-agent:references:in-reply-to:message-id:date :subject:cc:to:from:arc-authentication-results; bh=r1PWk9rHjUsKMlol5WUOX43RRvtQnqx+H+ag+yhuafg=; b=b4EWX0q8OgrAQatK11JiETSBfD1oQUwPsZOEIy0FIR0YuN9GOJlGf1E1wBwBxrkrG7 Vb/Dz+GUdRTAr48cbXf1OZMowj3LP94sOnjg0wmaS7gqZpZuT7yug8PLiRA61x7mbuDO a+s50W3nGMM02QUKCvWSQIt1avpwyEES5usoZDSEUFH27HrdRZGF0axWrfCKxXi3pQgQ 9W4tlAzgdT/wmDs/VHyEIQI1fPQRkTzjXIOUs64x3i21sTysaoIm45mRZGxe1VajHGwN lNbvaK9pcjDwYlRSGaJo5m39eBnOtGtqvKHSP9X/nINGROkewHvVd7eV9pInPJ1kdoAU NhKQ== ARC-Authentication-Results: i=1; mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 90.92.61.202 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 90.92.61.202 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Maxime Jayat , Ludovic Desroches , Vinod Koul Subject: [PATCH 4.16 119/196] dmaengine: at_xdmac: fix rare residue corruption Date: Sun, 22 Apr 2018 15:52:19 +0200 Message-Id: <20180422135110.396852301@linuxfoundation.org> X-Mailer: git-send-email 2.17.0 In-Reply-To: <20180422135104.278511750@linuxfoundation.org> References: <20180422135104.278511750@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-LABELS: =?utf-8?b?IlxcU2VudCI=?= X-GMAIL-THRID: =?utf-8?q?1598455126397049965?= X-GMAIL-MSGID: =?utf-8?q?1598455126397049965?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 4.16-stable review patch. If anyone has any objections, please let me know. ------------------ From: Maxime Jayat commit c5637476bbf9bb86c7f0413b8f4822a73d8d2d07 upstream. Despite the efforts made to correctly read the NDA and CUBC registers, the order in which the registers are read could sometimes lead to an inconsistent state. Re-using the timeline from the comments, this following timing of registers reads could lead to reading NDA with value "@desc2" and CUBC with value "MAX desc1": INITD -------- ------------ |____________________| _______________________ _______________ NDA @desc2 \/ @desc3 _______________________/\_______________ __________ ___________ _______________ CUBC 0 \/ MAX desc1 \/ MAX desc2 __________/\___________/\_______________ | | | | Events:(1)(2) (3)(4) (1) check_nda = @desc2 (2) initd = 1 (3) cur_ubc = MAX desc1 (4) cur_nda = @desc2 This is allowed by the condition ((check_nda == cur_nda) && initd), despite cur_ubc and cur_nda being in the precise state we don't want. This error leads to incorrect residue computation. Fix it by inversing the order in which CUBC and INITD are read. This makes sure that NDA and CUBC are always read together either _before_ INITD goes to 0 or _after_ it is back at 1. The case where NDA is read before INITD is at 0 and CUBC is read after INITD is back at 1 will be rejected by check_nda and cur_nda being different. Fixes: 53398f488821 ("dmaengine: at_xdmac: fix residue corruption") Cc: stable@vger.kernel.org Signed-off-by: Maxime Jayat Acked-by: Ludovic Desroches Signed-off-by: Vinod Koul Signed-off-by: Greg Kroah-Hartman --- drivers/dma/at_xdmac.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/drivers/dma/at_xdmac.c +++ b/drivers/dma/at_xdmac.c @@ -1471,10 +1471,10 @@ at_xdmac_tx_status(struct dma_chan *chan for (retry = 0; retry < AT_XDMAC_RESIDUE_MAX_RETRIES; retry++) { check_nda = at_xdmac_chan_read(atchan, AT_XDMAC_CNDA) & 0xfffffffc; rmb(); - initd = !!(at_xdmac_chan_read(atchan, AT_XDMAC_CC) & AT_XDMAC_CC_INITD); - rmb(); cur_ubc = at_xdmac_chan_read(atchan, AT_XDMAC_CUBC); rmb(); + initd = !!(at_xdmac_chan_read(atchan, AT_XDMAC_CC) & AT_XDMAC_CC_INITD); + rmb(); cur_nda = at_xdmac_chan_read(atchan, AT_XDMAC_CNDA) & 0xfffffffc; rmb();