From mboxrd@z Thu Jan 1 00:00:00 1970 From: kernel-TqfNSX0MhmxHKSADF0wUEw@public.gmane.org Subject: Re: [PATCH v4 2/4] spi: Split spi message into max_dma_len size chunks Date: Fri, 12 Apr 2019 12:03:35 +0200 Message-ID: References: <20190411164235.49771-1-noralf@tronnes.org> <20190411164235.49771-3-noralf@tronnes.org> <20190411181836.t2vuutqhjglsxsaz@wunner.de> <98571639-840a-494c-9e41-29ff89a22a8e@tronnes.org> <20190412094721.GE6909@sirena.org.uk> Mime-Version: 1.0 (Mac OS X Mail 9.3 \(3124\)) Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: dri-devel-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org, linux-spi , =?iso-8859-1?Q?Noralf_Tr=F8nnes?= , linux-rpi-kernel , meghana.madhyastha-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org To: Mark Brown Return-path: In-Reply-To: <20190412094721.GE6909-GFdadSzt00ze9xe1eoZjHA@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-rpi-kernel" Errors-To: linux-rpi-kernel-bounces+glkr-linux-rpi-kernel=m.gmane.org-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org List-Id: linux-spi.vger.kernel.org > On 12.04.2019, at 11:47, Mark Brown wrote: > > >> In a previous version of this I suggested to Meghana to put this in the >> driver, but Mark wanted it in the core. > > If we want to do this at a lower level the DMA code could hide this > limitation from the upper layers; presumably the SPI driver isn't the > only thing that might run into this. For clarification: There is a register of the SPI controller where you have to configure the number of bytes that it will request via DMA (primarily support transfers that are not a multiple of 4 - the data is transferred by DMA as words). So it is not really related to the general DMA implementation but to the DMA (request) support of the SPI controller. Martin