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Received: from n2100.armlinux.org.uk ([2001:4d48:ad52:3201:214:fdff:fe10:4f86]:46015) by pandora.armlinux.org.uk with esmtpsa (TLSv1.2:ECDHE-RSA-AES128-GCM-SHA256:128) (Exim 4.90_1) (envelope-from ) id 1ggo2x-00013m-81; Tue, 08 Jan 2019 09:51:43 +0000 Received: from linux by n2100.armlinux.org.uk with local (Exim 4.90_1) (envelope-from ) id 1ggo2r-00013Z-E7; Tue, 08 Jan 2019 09:51:37 +0000 Date: Tue, 8 Jan 2019 09:51:33 +0000 From: Russell King - ARM Linux To: JABLONSKY Jan Subject: Re: arm: dma-mapping: CPU may not see up-to-date data after DMA transaction Message-ID: <20190108095133.GP11171@n2100.armlinux.org.uk> References: <1542872133.26115.4.camel@atviedlbe741.rss.d3s.at.thales> <20181122092928.GF30658@n2100.armlinux.org.uk> <1542889465.26115.54.camel@atviedlbe741.rss.d3s.at.thales> <20181122125100.GG30658@n2100.armlinux.org.uk> <1542900920.26115.92.camel@atviedlbe741.rss.d3s.at.thales> <20181122165759.GH30658@n2100.armlinux.org.uk> <1546927833.511.68.camel@atviedlbe741.rss.d3s.at.thales> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <1546927833.511.68.camel@atviedlbe741.rss.d3s.at.thales> User-Agent: Mutt/1.5.23 (2014-03-12) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190108_015357_684448_FDA1440C X-CRM114-Status: GOOD ( 12.71 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Chris Cole , "linux-arm-kernel@lists.infradead.org" Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Jan 08, 2019 at 06:10:33AM +0000, JABLONSKY Jan wrote: > Hi again, > > I saw, that there are some findings in v7_dma_inv_range > https://patchwork.kernel.org/patch/10673097/ > > > It wouldn't be better to replace it directly with C&I ? No. > Otherwise still there is risk that you lost writes in->out ? > (Exactly happens in my case) For a region that is being used to DMA data _from_ the device, the data we have in the cache need not be written back out except if there are overlapping cache lines - writing it out would be a complete waste of bus bandwidth. -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up According to speedtest.net: 11.9Mbps down 500kbps up _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel