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Re: [PATCH v3 7/7] spi: imx: defer spi initialization, if DMA engine is pending

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On 05.11.2015 17:18, Anton Bondarenko wrote:
> On 05.11.2015 09:59, Sascha Hauer wrote:
>> On Sun, Nov 01, 2015 at 03:41:41PM +0100, Anton Bondarenko wrote:
>>> From: Anton Bondarenko <anton_bondarenko@mentor.com>
>>>
>>> If SPI device supports DMA mode, but DMA controller is not yet
>>> available due to e.g. a delay in the corresponding kernel module
>>> initialization, retry to initialize SPI driver later on instead of
>>> falling back into PIO only mode.
>>>
>>> Signed-off-by: Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>
>>> Signed-off-by: Anton Bondarenko <anton_bondarenko@mentor.com>
>>
>> Ok, so 6/7 is only part of the deferral story. Maybe squash the two
>> patches into one?
>>
>> Sascha
>
> I would like to keep these two changes separately since I have a small
> concern about this exact change.
>
> Let's assume such scenario:
> - ECSPI configured to use DMA in device tree and DMA controller
> description specified. But there is no driver for this controller in
> kernel.
> In this case dmaengine will always return -EDEFER and driver postpone
> spi-imx initialization. So finally there will be no SPI support even in
> PIO mode.
> Or for example spi-imx will be compiled into kernel, but DMA controller
> driver will be on SPI-NOR based rootfs.
>
> So the question is "Should we allow user to use incorrect combination of
> kernel configuration and DTS and work at least with some limitation?" Or
> should we try to guarantee device tree file requirement to use DMA.
>
> Any thoughts?
>
> Regards, Anton

Does anyone has other comments regarding this commit?

Regards, Anton
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[PATCH v3 0/7] Improvements for SPI IMX driver for Freescale IMX51, IMX53 and IMX6 Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-11-01 15:50 +0100
  [PATCH v3 5/7] spi: imx: Add support for loopback for ECSPI controllers Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-11-01 15:50 +0100
    Re: [PATCH v3 5/7] spi: imx: Add support for loopback for ECSPI  controllers Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-11-14 11:10 +0100
  [PATCH v3 6/7] spi: imx: return error from dma channel request Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-11-01 15:50 +0100
    Re: [PATCH v3 6/7] spi: imx: return error from dma channel request Sascha Hauer <s.hauer@pengutronix.de> - 2015-11-05 10:00 +0100
      Re: [PATCH v3 6/7] spi: imx: return error from dma channel request Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-11-05 17:10 +0100
        Re: [PATCH v3 6/7] spi: imx: return error from dma channel request Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-11-14 11:10 +0100
        Re: [PATCH v3 6/7] spi: imx: return error from dma channel request Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-11-14 11:10 +0100
  [PATCH v3 4/7] spi: imx: add function to check for IMX51 family controller Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-11-01 15:50 +0100
    Re: [PATCH v3 4/7] spi: imx: add function to check for IMX51 family  controller Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-11-14 11:10 +0100
  [PATCH v3 3/7] spi: imx: add support for all SPI word width for DMA transfer Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-11-01 15:50 +0100
  [PATCH v3 1/7] spi: imx: Fix DMA transfer Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-11-01 15:50 +0100
    Re: [PATCH v3 1/7] spi: imx: Fix DMA transfer Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-11-04 22:10 +0100
    Re: [PATCH v3 1/7] spi: imx: Fix DMA transfer Sascha Hauer <s.hauer@pengutronix.de> - 2015-11-05 09:40 +0100
      Re: [PATCH v3 1/7] spi: imx: Fix DMA transfer Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-11-05 18:00 +0100
        Re: [PATCH v3 1/7] spi: imx: Fix DMA transfer Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-11-14 11:10 +0100
  [PATCH v3 7/7] spi: imx: defer spi initialization, if DMA engine is pending Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-11-01 15:50 +0100
    Re: [PATCH v3 7/7] spi: imx: defer spi initialization, if DMA engine  is pending Sascha Hauer <s.hauer@pengutronix.de> - 2015-11-05 10:00 +0100
      Re: [PATCH v3 7/7] spi: imx: defer spi initialization, if DMA engine  is pending Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-11-05 17:20 +0100
        Re: [PATCH v3 7/7] spi: imx: defer spi initialization, if DMA engine  is pending Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-11-14 11:10 +0100
  [PATCH v3 2/7] spi: imx: replace fixed timeout with calculated one Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-11-01 15:50 +0100
    Re: [PATCH v3 2/7] spi: imx: replace fixed timeout with calculated  one Sascha Hauer <s.hauer@pengutronix.de> - 2015-11-05 09:50 +0100
      Re: [PATCH v3 2/7] spi: imx: replace fixed timeout with calculated  one Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-11-10 21:30 +0100
        Re: [PATCH v3 2/7] spi: imx: replace fixed timeout with calculated  one Sascha Hauer <s.hauer@pengutronix.de> - 2015-11-11 09:20 +0100
          Re: [PATCH v3 2/7] spi: imx: replace fixed timeout with calculated  one Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-11-14 11:10 +0100

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