[PATCH v5 1/2] usb: make xhci platform driver use 64 bit or 32 bit DMA

On Saturday 08 August 2015 13:31:02 Duc Dang wrote:

quoted

If we know that pdev->dev.dma_mask will always be initialised at this
point, then the above change is fine.  If not, it's introducing a
regression - dma_set_mask_and_coherent() will fail if pdev->dev.dma_mask
is NULL (depending on the architectures implementation of dma_set_mask()).

Prefixing the above change with the two lines I mention above would
ensure equivalent behaviour.  Even if we do want to get rid of this,
I'd advise to do it as a separate patch after this change, which can
be independently reverted if there's problems with its removal.

Hi Russell,

I will add the 2 lines you mentioned back to next version of the
patch. It is safer to do it that way as I do not see
pdev->dev.dma_mask gets initialized before the call
dma_set_mask_and_coherent  inside this xhci_plat.c file.

It would be good to add a WARN_ON() to the case where dma_mask
is a NULL pointer at the least. That way, we will at least
find out if there are some broken platforms that do not correctly
initialize the mask pointer.

	Arnd