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[211.20.114.70]) by smtp.gmail.com with ESMTPSA id 130-v6sm22296529pfz.174.2018.10.19.00.08.16 (version=TLS1_2 cipher=AES128-SHA bits=128/128); Fri, 19 Oct 2018 00:08:20 -0700 (PDT) Date: Fri, 19 Oct 2018 12:41:56 +0530 From: "sudheer.v" To: Benjamin Herrenschmidt Cc: Vinod , Rob Herring , Mark Rutland , Greg Kroah-Hartman , Joel Stanley , Andrew Jeffery , Russell King , Dan Williams , Jiri Slaby , Thomas Gleixner , Marc Zyngier , Christian Borntraeger , Michael Moese , Hendrik Brueckner , Kate Stewart , Philippe Ombredanne , dmaengine@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-aspeed@lists.ozlabs.org, Sudheer V , ShivahShankar Shakarnarayan rao Subject: Re: [[PATCH] 8/9] DMA-UART-Driver-for-AST2500 Message-ID: <20181019071154.GE13642@Pilot130> References: <1539749466-3912-1-git-send-email-open.sudheer@gmail.com> <1539749466-3912-9-git-send-email-open.sudheer@gmail.com> <20181017060531.GU2400@vkoul-mobl> <351eecd5b1b21893e94f76b34c058c6257b7f837.camel@kernel.crashing.org> <20181018095507.GC2400@vkoul-mobl> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 19, 2018 at 10:32:24AM +1100, Benjamin Herrenschmidt wrote: > On Thu, 2018-10-18 at 15:25 +0530, Vinod wrote: > > > > > It's not a dmaengine driver. It's a serial UART driver that happens to > > > use a dedicated DMA engine. > > > > Then I see no reason for it to use dmaengine APIs. The framework allows > > people to share a controller for many clients, but if you have dedicated > > one then you may use it directly > > Well... the engine is shared by a few UARTs, they have dedicated rings > but there's a common set of regs for interrupt handling etc. > > That said, I still think it could be contained within a UART driver, > there's little benefit in adding the framework overhead, esp since > these are really weak cores, any overhead will be felt. > > Ben. > > > > It's unclear whether it should be split into two drivers, or just have > > > the serial driver directly use the dma engine since that engine is > > > dedicated in HW to only work on those UARTs and nothing else... > > > > > > Cheers, > > > Ben. Initially we wanted to have a single driver, however we had an informal discussion with one of the maintainer and based on the feedback, followed the Linux DMA and UART architecture. If this seperate DMA-engine driver adds more overhead than benifit, we will merge them into a single UART driver and resubmitt the patches. Vinod, can this dma-controller driver sit under dma subsystem?. or better to move it under UART framework. Thank you. -- Sudheer