From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vinod Koul Subject: Re: [PATCH 1/7] dmaengine: at_xdmac: prefer usage of readl/writel_relaxed Date: Mon, 17 Nov 2014 14:04:00 +0530 Message-ID: <20141117083400.GS24582@intel.com> References: <1415875965-6905-1-git-send-email-ludovic.desroches@atmel.com> <1415875965-6905-2-git-send-email-ludovic.desroches@atmel.com> <2791155.z0l2TZezWO@wuerfel> <20141113153449.GO24582@intel.com> <20141113154551.GV3639@ldesroches-Latitude-E6320> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20141113154551.GV3639@ldesroches-Latitude-E6320> Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Arnd Bergmann , linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, dmaengine-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, cyrille.pitchen-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org, nicolas.ferre-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org List-Id: devicetree@vger.kernel.org On Thu, Nov 13, 2014 at 04:45:51PM +0100, Ludovic Desroches wrote: > On Thu, Nov 13, 2014 at 09:04:49PM +0530, Vinod Koul wrote: > > On Thu, Nov 13, 2014 at 12:01:49PM +0100, Arnd Bergmann wrote: > > > On Thursday 13 November 2014 11:52:39 Ludovic Desroches wrote: > > > > _relaxed version of readl and writel are not implemented on all > > > > architecture so COMPILE_TEST has to be removed in order to not cause > > > > some build failures. > > > > > > > > Signed-off-by: Ludovic Desroches > > > > --- > > > > > > > > > > I've queued up Will Deacon's series to enable the relaxed accessors > > > on all architectures, so the Kconfig change should no longer > > > be required in 3.19. > > And why is _relaxed() version required for thsi driver. Why cant readl(), > > writel() with barriers do? > > Required not but preferred to my mind. I don't need a barrier for all > read and write I am performing. Barriers have been added when needed. > > When you have fixed my code because of the compilation breakage on other > architecture, you only change the read and write macros. Currently, there are > some redundancies because of the barriers added in the code. > > To be honest, I have no idea about the performance impact between the > use of read/write and read/write_relaxed. Then two choices: > - go back to relaxed version, good new can keep COMPILE_TEST thanks to > Will Deacon But that would merged after merge window. This was also reported on next. So lets keep this patch for now and you can enabled COMPILE_TEST after next merge window. > - remove barrier since they are no more needed if using readl/writel I think that should be right fix along with checking performance of driver and optimize/stress it So for now, I am applying this whole series. -- ~Vinod -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html