From mboxrd@z Thu Jan 1 00:00:00 1970 From: "sudheer.v" Subject: Re: [[PATCH] 8/9] DMA-UART-Driver-for-AST2500 Date: Fri, 26 Oct 2018 12:37:28 +0530 Message-ID: <20181026070726.GA30088@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> <20181019071154.GE13642@Pilot130> <20181020162624.GC2894@vkoul-mobl> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20181020162624.GC2894@vkoul-mobl> Sender: linux-kernel-owner@vger.kernel.org To: Vinod Cc: Benjamin Herrenschmidt , 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 List-Id: devicetree@vger.kernel.org On Sat, Oct 20, 2018 at 09:56:24PM +0530, Vinod wrote: > On 19-10-18, 12:41, sudheer.v wrote: > > 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. > > > My advise would be to see what you can do with the DMA IP block. If this > can/would be used in different places then it would make sense to do a > dmaengine driver and solve the problem for everyone. > > If this is always going to be hidden behind serial then maybe it makes > sense to be inside serial driver and not use dmaengine APIs > > If you decide to prefer the former case, please move it to dmaengine and > resubmit :) > > HTH > -- > ~Vinod Hi All, As the DMA engine is dedicated only to UART,we have decided to rewrite the driver so that no code will come under drivers/dma. I will resubmitt the patches after merging dma controller code and uart driver code. Regards -sudheer