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From: Mark Brown <broonie-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
To: Andy Shevchenko
	<andriy.shevchenko-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
Cc: Vinod Koul <vinod.koul-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>,
	dmaengine-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-spi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: [PATCH 02/10] spi: dw-mid: always use duplex transfers when DMA
Date: Wed, 24 Sep 2014 12:07:47 +0100	[thread overview]
Message-ID: <20140924110747.GG16977@sirena.org.uk> (raw)
In-Reply-To: <1411554747.30231.10.camel-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>

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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.

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  parent reply	other threads:[~2014-09-24 11:07 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-09-18 17:08 [PATCH 00/10] spi: dw: make DMA working Andy Shevchenko
     [not found] ` <1411060140-2801-1-git-send-email-andriy.shevchenko-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
2014-09-18 17:08   ` [PATCH 01/10] spi: dw-mid: respect 8 bit mode Andy Shevchenko
     [not found]     ` <1411060140-2801-2-git-send-email-andriy.shevchenko-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
2014-09-24  8:49       ` Mark Brown
2014-09-18 17:08   ` [PATCH 02/10] spi: dw-mid: always use duplex transfers when DMA Andy Shevchenko
     [not found]     ` <1411060140-2801-3-git-send-email-andriy.shevchenko-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
2014-09-24  8:44       ` Mark Brown
     [not found]         ` <20140924084407.GF4015-GFdadSzt00ze9xe1eoZjHA@public.gmane.org>
2014-09-24 10:32           ` Andy Shevchenko
     [not found]             ` <1411554747.30231.10.camel-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
2014-09-24 11:07               ` Mark Brown [this message]
     [not found]                 ` <20140924110747.GG16977-GFdadSzt00ze9xe1eoZjHA@public.gmane.org>
2014-09-24 12:02                   ` Andy Shevchenko
2014-09-18 17:08   ` [PATCH 03/10] spi: dw-mid: terminate ongoing transfers at exit Andy Shevchenko
     [not found]     ` <1411060140-2801-4-git-send-email-andriy.shevchenko-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
2014-09-24  8:49       ` Mark Brown
2014-09-18 17:08   ` [PATCH 04/10] spi: dw-mid: follow new DMAengine workflow Andy Shevchenko
     [not found]     ` <1411060140-2801-5-git-send-email-andriy.shevchenko-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
2014-09-24  8:44       ` Mark Brown
     [not found]         ` <20140924084453.GG4015-GFdadSzt00ze9xe1eoZjHA@public.gmane.org>
2014-09-24 10:35           ` Andy Shevchenko
     [not found]             ` <1411554938.30231.12.camel-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
2014-09-24 11:08               ` Mark Brown
     [not found]                 ` <20140924110849.GH16977-GFdadSzt00ze9xe1eoZjHA@public.gmane.org>
2014-09-24 11:59                   ` Andy Shevchenko
2014-09-18 17:08   ` [PATCH 05/10] spi: dw: disable all interrupts first when pump message Andy Shevchenko
     [not found]     ` <1411060140-2801-6-git-send-email-andriy.shevchenko-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
2014-09-24  8:47       ` Mark Brown
     [not found]         ` <20140924084724.GH4015-GFdadSzt00ze9xe1eoZjHA@public.gmane.org>
2014-09-24 10:38           ` Andy Shevchenko
2014-09-18 17:08   ` [PATCH 06/10] spi: dw: introduce support of loopback mode Andy Shevchenko
     [not found]     ` <1411060140-2801-7-git-send-email-andriy.shevchenko-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
2014-09-24  8:49       ` Mark Brown
2014-09-18 17:08   ` [PATCH 07/10] spi: dw: fix style of code in few places Andy Shevchenko
     [not found]     ` <1411060140-2801-8-git-send-email-andriy.shevchenko-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
2014-09-24  8:50       ` Mark Brown
2014-09-18 17:08   ` [PATCH 08/10] spi: dw-mid: move to use core SPI DMA mappings Andy Shevchenko
2014-09-18 17:08   ` [PATCH 09/10] spi: dw-mid: convert to use dw_dmac instead of intel_mid_dma Andy Shevchenko
2014-09-18 17:09   ` [PATCH 10/10] dmaengine: intel-mid-dma: remove the driver Andy Shevchenko
     [not found]     ` <1411060140-2801-11-git-send-email-andriy.shevchenko-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
2014-10-15 15:07       ` Vinod Koul
     [not found]         ` <20141015150727.GX1638-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
2014-10-16  8:12           ` Shevchenko, Andriy

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