Re: [PATCH 2/5] i2c: sh_mobile: add DMA support

[Vinod Koul <vinod.koul-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>]

On Thu, Dec 11, 2014 at 11:52:10PM +0200, Laurent Pinchart wrote:
> On Thursday 11 December 2014 22:47:32 Wolfram Sang wrote:
> > > > Note that the I2C drives uses subsys_initcall() for historic reasons,
> > > > while the DMA driver uses module_init(). This is hard to revert without
> > > > introducing potential regressions on older boards. So, the I2C DMA
> > > > support needs to handle deferred probe definately. I am with Laurent, I
> > > > don't see any other way, but I'd be glad to be enlightened...
> > > 
> > > While I believe that requesting the channel at transfer time is the good
> > > solution, I think we should still try to move to module initcalls where
> > > possible. The risk of regressions is real so proper testing is needed. My
> > > question is, have you tried it ?
> > 
> > I would need to test all boards using this driver to not fail booting.
> > Usually I2C drivers are moved to subsys_initcall because they need
> > access to something critical (PMIC, GPIOs...) early. I don't see a sane
> > way to do that testing.
> 
> Still, I would like to get a better view on the problems we should expect, by 
> testing this on the latest boards for instance.
> 
> > Other than that, even if we move to module_init, we reduce the chance of
> > getting a deferred probe, but we do not eliminate it...
> 
> Sure, but reducing the chance of deferred probe is a good idea in my opinion 
> :-)
Okay so what is the issue here, this statement is a bit worrying. Why do
you guys want to reduce the chance of deferred probe? I assumed that issue was
the channels availability...

-- 
~Vinod