From mboxrd@z Thu Jan 1 00:00:00 1970 From: plaes@plaes.org (Priit Laes) Date: Thu, 02 Jun 2016 07:42:26 +0300 Subject: [linux-sunxi] Re: [PATCH 5/5] RFC spi: sun4i: add DMA support In-Reply-To: <20160601180056.GA4908@lukather> References: <20160530112610.GJ29837@sirena.org.uk> <20160530150343.GL29837@sirena.org.uk> <20160530155016.GO29837@sirena.org.uk> <20160601180056.GA4908@lukather> Message-ID: <1464842546.23881.3.camel@plaes.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Wed, 2016-06-01 at 20:00 +0200, Maxime Ripard wrote: > Hi, > > On Mon, May 30, 2016 at 04:50:16PM +0100, Mark Brown wrote: > > > > On Mon, May 30, 2016 at 05:28:10PM +0200, Michal Suchanek wrote: > > > > > > On 30 May 2016 at 17:03, Mark Brown wrote: > > > > > > > > > > > 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 > > > > > > 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???I 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. > > 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. > Actually it non-DMA case works fine if you don't need SPI transfers larger than?SUN4I_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