linux-kernel - Re: [PATCH 1/4] dmaengine: dw_dmac: use helper macro module_platform

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Date:	Wed, 10 Oct 2012 15:40:02 +0300
From:	Felipe Balbi <balbi@...com>
To:	Andy Shevchenko <andy.shevchenko@...il.com>
Cc:	viresh kumar <viresh.kumar@...aro.org>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Vinod Koul <vinod.koul@...el.com>,
	linux-kernel@...r.kernel.org,
	spear-devel <spear-devel@...t.st.com>, balbi@...com,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>
Subject: Re: [PATCH 1/4] dmaengine: dw_dmac: use helper macro
 module_platform_driver()

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@...aro.org> wrote:
> > On Wed, Oct 10, 2012 at 2:34 PM, Andy Shevchenko
> > <andriy.shevchenko@...ux.intel.com> wrote:
> >> On Tue, 2012-10-02 at 14:41 +0300, Andy Shevchenko wrote:
> >>> From: Heikki Krogerus <heikki.krogerus@...ux.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.

-- 
balbi

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