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boundary="----wn.C777VfLFf0j4dI6teQ5O7yZ9hP4.it_WB71vmM7CNsG.7=_30f47_" X-Sendblock-Type: AUTO_CONFIDENTIAL CMS-TYPE: 102P DLP-Filter: Pass X-CFilter-Loop: Reflected X-CMS-RootMailID: 20200818075050epcas2p15c780650f5f6b4a54ce731c273d24c98 References: <1597736591-20457-1-git-send-email-pullip.cho@samsung.com> <20200818082852.GA15145@willie-the-truck> <20200818093739.GB191752@KEI> <20200818100756.GA15543@willie-the-truck> <20200818161006.GA25124@infradead.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200818_220910_525500_1545D91A X-CRM114-Status: GOOD ( 30.75 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: janghyuck.kim@samsung.com, catalin.marinas@arm.com, linux-kernel@vger.kernel.org, hyesoo.yu@samsung.com, iommu@lists.linux-foundation.org, Will Deacon , linux-arm-kernel@lists.infradead.org, robin.murphy@arm.com Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org ------wn.C777VfLFf0j4dI6teQ5O7yZ9hP4.it_WB71vmM7CNsG.7=_30f47_ Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline On Tue, Aug 18, 2020 at 05:10:06PM +0100, Christoph Hellwig wrote: > On Tue, Aug 18, 2020 at 11:07:57AM +0100, Will Deacon wrote: > > > > so I'm not sure > > > > that we should be complicating the implementation like this to try to > > > > make it "fast". > > > > > > > I agree that this patch makes the implementation of dma API a bit more > > > but I don't think this does not impact its complication seriously. > > > > It's death by a thousand cuts; this patch further fragments the architecture > > backends and leads to arm64-specific behaviour which consequently won't get > > well tested by anybody else. Now, it might be worth it, but there's not > > enough information here to make that call. > > So it turns out I misread the series (*cough*, crazy long lines, > *cough*), and it does not actually expose a new API as I thought, but > it still makes a total mess of the internal interface. It turns out > that on the for cpu side we already have arch_sync_dma_for_cpu_all, > which should do all that is needed. We could do the equivalent for > the to device side, but only IFF there really is a major benefit for > something that actually is mainstream and matters. > Indeed, arch_sync_dma_for_cpu_all() is used where the new internal API arch_sync_barrier_for_cpu() should be called. I just thought it is a special hook for MIPS. In the next version of the patch series, I should consider using arch_sync_dma_for_cpu_all() and introducting its 'for_dev' version with some performance data to show the benefit of the change. Thank you for the proposal. KyongHo ------wn.C777VfLFf0j4dI6teQ5O7yZ9hP4.it_WB71vmM7CNsG.7=_30f47_ Content-Type: text/plain; charset="utf-8" ------wn.C777VfLFf0j4dI6teQ5O7yZ9hP4.it_WB71vmM7CNsG.7=_30f47_ Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel ------wn.C777VfLFf0j4dI6teQ5O7yZ9hP4.it_WB71vmM7CNsG.7=_30f47_--