linux-kernel - Re: [PATCH v6 07/12] usb: chipidea: add a usb2 driver for ci13xxx

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Date:	Tue, 23 Sep 2014 18:44:40 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Antoine Tenart <antoine.tenart@...e-electrons.com>
Cc:	linux-arm-kernel@...ts.infradead.org,
	sebastian.hesselbarth@...il.com, Peter.Chen@...escale.com,
	balbi@...com, p.zabel@...gutronix.de,
	thomas.petazzoni@...e-electrons.com, zmxu@...vell.com,
	devicetree@...r.kernel.org, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org, alexandre.belloni@...e-electrons.com,
	jszhang@...vell.com
Subject: Re: [PATCH v6 07/12] usb: chipidea: add a usb2 driver for ci13xxx

On Tuesday 23 September 2014 15:36:45 Antoine Tenart wrote:
> On Tue, Sep 23, 2014 at 12:39:04PM +0200, Arnd Bergmann wrote:
> > On Tuesday 23 September 2014 12:28:03 Antoine Tenart wrote:
> > > +       if (dev->of_node) {
> > > +               ret = ci_hdrc_usb2_dt_probe(dev, ci_pdata);
> > > +               if (ret)
> > > +                       goto clk_err;
> > > +       } else {
> > > +               ret = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(32));
> > > +               if (ret)
> > > +                       goto clk_err;
> > > +       }
> > > 
> > 
> > Why do you care about the non-DT case here? I think it would be nicer to
> > open-code the ci_hdrc_usb2_dt_probe() function in here and remove
> > the dma_set_mask_and_coherent(), which should not even be necessary for
> > the case where you have a hardwired platform device.
> > 
> 
> I thought we agreed to call dma_set_mask_and_coherent():
> http://lists.infradead.org/pipermail/linux-arm-kernel/2014-July/273335.html
> 
> I do not have a strong opinion on this as I only use the dt case for my
> usage.

The question is more about who actually wants the non-DT case.

Since this is a new driver, I suspect that the answer is "nobody",
as the existing board files are all for legacy platforms that we
are not going to adapt for this driver.

I see in the thread that at least Peter Chen was assuming the non-DT
case was still needed, but I can't find a reason for this in the code.
If we no longer care about that, the call to dev_get_platdata()
can also get removed.

Looking through the code some more, I also notice that it's using
a strange way of doing the abstraction: ci_hdrc_add_device()
actually creates a child device node, while the preferred way would
be to just call into ci_hdrc_probe(), or a generalized version of
that.
That should probably be changed, but can be done as a later cleanup.


	Arnd
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