From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andy Shevchenko Subject: Re: [PATCH 02/10] spi: dw-mid: always use duplex transfers when DMA Date: Wed, 24 Sep 2014 15:02:12 +0300 Message-ID: <1411560132.22587.0.camel@linux.intel.com> References: <1411060140-2801-1-git-send-email-andriy.shevchenko@linux.intel.com> <1411060140-2801-3-git-send-email-andriy.shevchenko@linux.intel.com> <20140924084407.GF4015@sirena.org.uk> <1411554747.30231.10.camel@linux.intel.com> <20140924110747.GG16977@sirena.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Vinod Koul , dmaengine-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-spi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Mark Brown Return-path: In-Reply-To: <20140924110747.GG16977-GFdadSzt00ze9xe1eoZjHA@public.gmane.org> Sender: linux-spi-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: On Wed, 2014-09-24 at 12:07 +0100, Mark Brown wrote: > On Wed, Sep 24, 2014 at 01:32:27PM +0300, Andy Shevchenko wrote: > > On Wed, 2014-09-24 at 09:44 +0100, Mark Brown wrote: > > > On Thu, Sep 18, 2014 at 08:08:52PM +0300, Andy Shevchenko wrote: > > > > > In case of DMA we never got things done until we enable both channels. In case > > > > of receive only or send only mode the user has to provide a dummy buffer. > > > > The driver must never impose such requirements on clients, they > > > shouldn't need to know about the quirks of the controller. There's > > > support in the core providing dummy buffers for transmit and receive, > > > you should use that (possibly extending it so the dummies are only > > > provided for DMA). > > > Currently driver in case of receiving or sending only will never call > > the xfer_done from DMA callback since we never will have counter equal > > to 2. So, the driver already relies on duplex mode. Am I missing > > something? > > Please re-read what I wrote above, especially the first phrase. You > can't require that we rewrite essentialy every SPI driver on the off > chance that it's used with this controller. I think I know how to satisfy the user and fix the driver. I will remake the approach. -- Andy Shevchenko Intel Finland Oy -- To unsubscribe from this list: send the line "unsubscribe linux-spi" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html