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    SubjectRe: [PATCH 1/4] dmaengine: dw_dmac: use helper macro module_platform_driver()
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    On Wed, Oct 10, 2012 at 3:40 PM, Felipe Balbi <balbi@ti.com> wrote:
    > On Wed, Oct 10, 2012 at 12:21:04PM +0300, Andy Shevchenko wrote:
    >> On Wed, Oct 10, 2012 at 12:08 PM, viresh kumar <viresh.kumar@linaro.org> wrote:
    >> > On Wed, Oct 10, 2012 at 2:34 PM, Andy Shevchenko
    >> > <andriy.shevchenko@linux.intel.com> wrote:
    >> >> On Tue, 2012-10-02 at 14:41 +0300, Andy Shevchenko wrote:
    >> >>> From: Heikki Krogerus <heikki.krogerus@linux.intel.com>
    >> >>>
    >> >>> Since v3.2 we have nice macro to define the platform driver's init and exit
    >> >>> calls. This patch simplifies the dw_dmac driver by using that macro.
    >> >>
    >> >> Actually we can't do this. It will break initialization of some other
    >> >> drivers.
    >> >
    >> > why?
    >>
    >> We have spi, i2c and hsuart devices connected to the DMA controller.
    >> In case we would like to use DMA we have to have the dw_dmac loaded
    >> before them. Currently we have spi driver on subsys_initcall level,
    >> and Mika, who is developing it, will change to module_init_call level.
    >> However, it will just hide the potential issue. He also tried to use
    >> deferred module loading, but we don't know if it's good solution or
    >> not, and that solution requires something to stop deferring at some
    >> moment.
    >>
    >> Might be we missed something and there is a better solution.
    >
    > if they can only work with DMA, they should return -EPROBE_DEFER so
    > their probe() function can be called after DMA driver has finished
    > probing.

    They could work either with DMA or via PIO mode.
    How does the driver know when to stop to return -EPROBE_DEFER?

    --
    With Best Regards,
    Andy Shevchenko


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