From mboxrd@z Thu Jan 1 00:00:00 1970 From: Priit Laes Subject: Re: Re: [PATCH 5/5] RFC spi: sun4i: add DMA support Date: Thu, 02 Jun 2016 07:42:26 +0300 Message-ID: <1464842546.23881.3.camel@plaes.org> References: <20160530112610.GJ29837@sirena.org.uk> <20160530150343.GL29837@sirena.org.uk> <20160530155016.GO29837@sirena.org.uk> <20160601180056.GA4908@lukather> Reply-To: plaes-q/aMd4JkU83YtjvyW6yDsg@public.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Cc: Michal Suchanek , Geert Uytterhoeven , linux-sunxi , Chen-Yu Tsai , linux-spi , "linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" To: maxime.ripard-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org, Mark Brown Return-path: Sender: linux-sunxi-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org In-Reply-To: <20160601180056.GA4908@lukather> List-Post: , List-Help: , List-Archive: , List-Unsubscribe: , List-Id: linux-spi.vger.kernel.org On Wed, 2016-06-01 at 20:00 +0200, Maxime Ripard wrote: > Hi, >=20 > On Mon, May 30, 2016 at 04:50:16PM +0100, Mark Brown wrote: > >=20 > > On Mon, May 30, 2016 at 05:28:10PM +0200, Michal Suchanek wrote: > > >=20 > > > On 30 May 2016 at 17:03, Mark Brown wrote: > > >=20 > > > >=20 > > > > I really don't think it's worth caring too much about cases > > > > where the > > > > DMA driver hasn't been compiled in, it's not like SPI is the > > > > only thing > > >=20 > > > It's what the driver did to start with and it was requested to > > > fall > > > back to non-DMA in the case DMA is not available. > > Why?=C2=A0=C2=A0I really can't see any sensible use case for this that > > doesn't > > have a better solution available. > SPI works just fine without DMA, which might just be considered an > (optional) optimisation. >=20 > We've been using it without DMA for years now, and it was working > just > fine, and it will work even better with the other patches in this > serie. There's no reason to add a hard dependency on something that > we > don't really need. >=20 Actually it non-DMA case works fine if you don't need SPI transfers larger than=C2=A0SUN4I_FIFO_DEPTH - 1, which is 63 bytes. This was addressed by this patch, but was never applied: http://permalink.gmane.org/gmane.linux.kernel.spi.devel/18950 --=20 You received this message because you are subscribed to the Google Groups "= linux-sunxi" group. To unsubscribe from this group and stop receiving emails from it, send an e= mail to linux-sunxi+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org For more options, visit https://groups.google.com/d/optout.