[alsa-devel] [RESEND PATCH v2 14/15] ASoC: qcom: apq8096: Add db820c machine driver

[Srinivas Kandagatla]

On 03/01/18 19:41, Stephen Boyd wrote:
>>>> +	ret = dma_coerce_mask_and_coherent(card->dev, DMA_BIT_MASK(32));
>>> Why do we need to do this? Can you add some sort of comment in the code
>>> about why?
>> Even though dsp supports 64 bit addresses, but the sid sits at
>> offset of 32, which brings this restriction of supporting only 32
>> bit iova.
>>
> Doesn't the dsp have an iommu in place to make the address
> translation from 64 to 32 bits transparent? I thought this was
> what dma-ranges and iommu binding was for, but I'm not well
> versed on all the details here.
Thanks for reminding, dma-ranges would work too, I will give that a go 
in next version.

--srini