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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7E68BC433F5 for ; Mon, 13 Dec 2021 14:18:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238486AbhLMOSR (ORCPT ); Mon, 13 Dec 2021 09:18:17 -0500 Received: from ams.source.kernel.org ([145.40.68.75]:34218 "EHLO ams.source.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231897AbhLMOSR (ORCPT ); Mon, 13 Dec 2021 09:18:17 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id B18CEB81062; Mon, 13 Dec 2021 14:18:15 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B5CBEC34602; Mon, 13 Dec 2021 14:18:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1639405094; bh=NtWdzlEjft5tnQeFaBXUVrmubHd8T7HRkrRLfS+HxKc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ef4dtFt35n0BNeZHb5cwHF2nWR84NPJ4B4Ej+DcAmvR7/HzogwktH/W/meMnZnx1/ Xg3O6A+RredIYQtKTQ5Xmko6sTk52Ckx/QDevDNiQkd9m6eeVOhNiVRfdPIU5wthcz kslBCgGFDpF4EoLzXiuVfEO/wBb1eXc3RIOJDVQs= Date: Mon, 13 Dec 2021 15:18:11 +0100 From: Greg Kroah-Hartman To: Chunfeng Yun Cc: Matthias Brugger , linux-usb@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org, Eddie Hung , Yuwen Ng , stable@vger.kernel.org Subject: Re: [PATCH 2/3] usb: mtu3: add memory barrier before set GPD's HWO Message-ID: References: <20211209031424.17842-1-chunfeng.yun@mediatek.com> <20211209031424.17842-2-chunfeng.yun@mediatek.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20211209031424.17842-2-chunfeng.yun@mediatek.com> Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On Thu, Dec 09, 2021 at 11:14:23AM +0800, Chunfeng Yun wrote: > There is a seldom issue that the controller access invalid address > and trigger devapc or emimpu violation. That is due to memory access > is out of order and cause gpd data is not correct. > Make sure GPD is fully written before giving it to HW by setting its > HWO. > > Fixes: 48e0d3735aa5 ("usb: mtu3: supports new QMU format") > Cc: stable@vger.kernel.org > Reported-by: Eddie Hung > Signed-off-by: Chunfeng Yun > --- > drivers/usb/mtu3/mtu3_qmu.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/drivers/usb/mtu3/mtu3_qmu.c b/drivers/usb/mtu3/mtu3_qmu.c > index 3f414f91b589..34bb5ac67efe 100644 > --- a/drivers/usb/mtu3/mtu3_qmu.c > +++ b/drivers/usb/mtu3/mtu3_qmu.c > @@ -273,6 +273,8 @@ static int mtu3_prepare_tx_gpd(struct mtu3_ep *mep, struct mtu3_request *mreq) > gpd->dw3_info |= cpu_to_le32(GPD_EXT_FLAG_ZLP); > } > > + /* make sure GPD is fully written before giving it to HW */ > + mb(); So this means you are using mmio for this structure? If so, shouldn't you be using normal io memory read/write calls as well and not just "raw" pointers like this: > gpd->dw0_info |= cpu_to_le32(GPD_FLAGS_IOC | GPD_FLAGS_HWO); Are you sure this is ok? Sprinkling around mb() calls is almost never the correct solution. If you need to ensure that a write succeeds, shouldn't you do a read from it afterward? Many busses require this, doesn't yours? > > mreq->gpd = gpd; > @@ -306,6 +308,8 @@ static int mtu3_prepare_rx_gpd(struct mtu3_ep *mep, struct mtu3_request *mreq) > gpd->next_gpd = cpu_to_le32(lower_32_bits(enq_dma)); > ext_addr |= GPD_EXT_NGP(mtu, upper_32_bits(enq_dma)); > gpd->dw3_info = cpu_to_le32(ext_addr); > + /* make sure GPD is fully written before giving it to HW */ > + mb(); Again, mb(); does not ensure that memory-mapped i/o actually hits the HW. Or if it does on your platform, how? mb() is a compiler barrier, not a memory write to a bus barrier. Please read Documentation/memory-barriers.txt for more details. thanks, greg k-h