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

Arnd Bergmann
2014-09-30T13:43:48Z

On Tuesday 30 September 2014 20:39:34 Peter Chen wrote:
> Thanks, Arnd. I had not thought setting dma mask is so complicated, yes, it
> should check the return value, two things to confirm:
>
> - dma_coerce_mask_and_coherent or dma_set_mask_and_coherent, the only difference
> of these two API is the first one do "dev->dma_mask = &dev->coherent_dma_mask;"
> The reason you suggest choosing dma_set_mask_and_coherent is you do not want
> assign dev->dma_mask?

No, that is just the current definition on ARM32 with CONFIG_ARCH_MULTIPLATFORM, and
that is going to change soon to be DT aware.
dma_set_mask_and_coherent() is supposed to check whether the platform can support
the respective mask and return an error if it cannot.

> - The second parameter for dma_set_mask_and_coherent is DMA_BIT_MASK(32), is it
> ok?
>
> I just a little confused of what's the operation is "hardcoding the dma mask"?

dma_coerce_mask_and_coherent() will hardcode the dma mask and override whatever
the platform says is necessary.

Arnd