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

Arnd Bergmann
2014-09-25T07:11:47Z

On Thursday 25 September 2014 09:16:48 Peter Chen 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;
> > + }
>
> Hi Antoine, the above code may not be needed, since get phy and set dma
> mask are common operation, we can do it at core code, the only thing you
> need to do is something like: dev->dma_mask = DMA_BIT_MASK(32).
>

Certainly not, doing that would be broken for a number of reasons:

- dev->dma_mask is a pointer, a driver should not reassign that
- the device may have been set up for a bus that requires a smaller mask
that is already set, changing the mask would cause data corruption
- setting just the dma mask but not coherent mask is wrong
- setting the dma mask can fail, e.g. if the mask is smaller than the
smallest memory zone, so you have to check the return value.

Arnd