From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AIpwx49qdGaTZY9nfhc+mPxVH+7nM8KDGw7SR7youBfEvWR1oA9NIsBGbDz/duHMJJ0oNK35Ky4v ARC-Seal: i=1; a=rsa-sha256; t=1523954706; cv=none; d=google.com; s=arc-20160816; b=yWj7fgX2rz8mAsFRIeBKTUGYQcphuG6BGDGnPiyXuISBjcPCnKmNb3q3ES7SMEtMVu uKzpJh+RrxCr/a0w8p7+w88M+51LOXkzvivyEBwsJ5mOFT446S6946Q9b+UfTuUPUmfY GZug1Vcu9/Y9EE8oaq8HR2XPrGjGNr8OwrwrNzdD+IVUI3NVdxfTm0YE6YUJwswskZ8e N7/C0+un7hZMz3vyxkFkyWP/QbT2iWwWQwPGSFNz/7b5iF5jRR4HEq85CEHUNLRCQEes n5ftfXFgXid49VPkx3W3r35rAIieKxDb0EFTgJmwjHxqn6hCcbmngtgDUnq4C30kn4K8 wz1A== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=content-language:thread-index:content-transfer-encoding :mime-version:message-id:date:subject:cc:to:from :arc-authentication-results; bh=ihsfGQsSzOzLpy1WU5m4pnBxPrxY6W8kYB78qdoja40=; b=0eS5+RknII3L2pcNK46pu7mBFS9KDE9BDlZA5HdIQjXoxw5qS+hO+XbG9M653Tf2t1 DS9X+mWtL5vEROPwRnPhU5n4Gpune2iABeChWppqWTYIoxGS3/fKs0BnWGYl1giJT3wQ D5VKQnqJl8g8IRQTXPpl3lKnfjL/bkwA8AaPM9um/+YJ6N1hB/WWqqpRS/KBW67dpfVK lycWBMzMhw0zFqHCHOSsyRQKmxHx54Tvg+EhLTSBO9mjOVdAOzUljKHvj4V6yWVaCzst XrCOFrhwOCwhVvtIAXV+cAlzkB8DVoTLupRamllODjfVUht4h7z+TtrLZLEreRQaSQ46 z8hw== ARC-Authentication-Results: i=1; mx.google.com; spf=neutral (google.com: 180.169.121.91 is neither permitted nor denied by best guess record for domain of davidwang@zhaoxin.com) smtp.mailfrom=DavidWang@zhaoxin.com Authentication-Results: mx.google.com; spf=neutral (google.com: 180.169.121.91 is neither permitted nor denied by best guess record for domain of davidwang@zhaoxin.com) smtp.mailfrom=DavidWang@zhaoxin.com From: David Wang To: 'Christoph Hellwig' CC: , , , , , , , , , , , Subject: Re: [PATCH] x86/dma-mapping: override via_no_dac for new VIA PCI bridges Date: Tue, 17 Apr 2018 16:44:32 +0800 Message-ID: <000001d3d628$4e91a4c0$ebb4ee40$@zhaoxin.com> MIME-Version: 1.0 Content-Type: text/plain; charset="gb2312" Content-Transfer-Encoding: quoted-printable X-Mailer: Microsoft Outlook 16.0 Thread-Index: AdPWJWP7w0EjoZkeTnm5pu211P7x3g== Content-Language: zh-cn X-Originating-IP: [10.29.8.18] X-ClientProxiedBy: zxbjmbx1.zhaoxin.com (10.29.252.163) To zxbjmbx3.zhaoxin.com (10.29.252.165) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1597894379144798679?= X-GMAIL-MSGID: =?utf-8?q?1597982329344314331?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: > -----=D3=CA=BC=FE=D4=AD=BC=FE----- > =B7=A2=BC=FE=C8=CB: Christoph Hellwig [mailto:hch@infradead.org] > =B7=A2=CB=CD=CA=B1=BC=E4: 2018=C4=EA4=D4=C216=C8=D5 20:34 > =CA=D5=BC=FE=C8=CB: David Wang > =B3=AD=CB=CD: tglx@linutronix.de; mingo@redhat.com; hpa@zytor.com; > gregkh@linuxfoundation.org; x86@kernel.org; linux- > kernel@vger.kernel.org; brucechang@via-alliance.com; > cooperyan@zhaoxin.com; qiyuanwang@zhaoxin.com; > benjaminpan@viatech.com; lukelin@viacpu.com; timguo@zhaoxin.com > =D6=F7=CC=E2: Re: [PATCH] x86/dma-mapping: override via_no_dac for new = VIA PCI > bridges >=20 > On Mon, Apr 16, 2018 at 05:26:56PM +0800, David Wang wrote: > > PCI bridges integrated in new VIA chipset/SoC have no DAC issue. > > Enable DAC for the platforms with these chipset/SoC can improve DMA > > performance about 20% when DRAM size > 4GB. > > >=20 > So we get an exception to an exception? Is there any way to figure = out the > PCI IDs actually affected? Yes. Do you mean we should list the PCI IDs of the PCI bridges which have no = DAC issue? There are lots of PCI bridges(PCIE root ports) in our new chipsets/SoCs. = And no DMA issues found.=20 So, we only want to recognize the chipset/SoC by reading VID/DID of Bus = 0, Device 17, function 0. Thx. --- David