[PATCH v3 07/12] usb: chipidea: add a usb2 driver for ci13xxx

[Peter Chen]

> >
> > Some people wanted the possibility to set the DMA mask as this USB2 CI
> > driver does not do specific Berlin operation and can be reused later.
> > I don't particularly need to call dma_coerce_mask_and_coherent() in my
> > case, as far as I know.
> 
> Ok, just remove the call then and rely on the default mask.
> 
> > They can maybe give the restrictions they might want to put on the DMA
> > mask.
> 
> If the restriction is from the bus, it should get handled automatically
> by the device probe as long as the correct dma-ranges property is there
> (though we have a small bug there at the moment). If there is a variation
> of ci13xxx that can't do 32-bit DMA, that should use a different
> compatible string and pass a fixed mask into dma_set_mask_and_coherent()
> based on the device.
> 

Correct me if my below understanding is wrong please.

For three chipidea users:
user_a: don't need dma mask
user_b: dma mask value is dma_mask_b
user_c: dma mask value is dma_mask_c

We don't need to call dma_coerce_mask_and_coherent() at generic chipidea
glue driver, and set dma-ranges as dma_mask_b at user_b's dts, and set
dma-ranges as dma_mask_c at user_c's dts.

Peter