[PATCH] ARM: mach-imx: sdhci-esdhc-imx: initialize DMA mask

[Russell King - ARM Linux]

On Tue, Apr 12, 2016 at 12:59:14PM +0300, Adrian Hunter wrote:
> On 12/04/16 11:40, Russell King - ARM Linux wrote:
> > What do you mean "doesn't need a dma_mask" ?  DMA _always_ requires a
> > DMA mask.  The DMA mask defines how many address bits are capable of
> > being used on the bus.
> > 
> > If there's no DMA mask, then there's no usable address bits, and so
> > the device is not DMA capable.  Hence, dma_set_mask_and_coherent()
> > will fail because its not possible to negotiate a non-zero number of
> > address bits.
> > 
> 
> The point is, now we valid dma_set_mask_and_coherent(), DMA will stop
> working for any other SDHCI device that hasn't allocated dev.dma_mask.  Is
> that OK?

Two latent bugs.

1) Any device that doesn't have dma_mask allocated isn't capable of
   streaming DMA, but may be capable of coherent DMA - a device which
   is capable _should_ have a defaulted dma_mask setup.

2) Drivers must always use the dma_set_mask*() family of functions
   if they intend to use DMA.

Requirement (2) is nothing new, and predates MMC as a whole, so it's
a long-standing latent bug.


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