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

On 01/03, Srinivas Kandagatla wrote:

Thanks for your review comments,

On 03/01/18 17:20, Stephen Boyd wrote:

...

...

• return ret;

+}

+static int msm_snd_apq8096_probe(struct platform_device *pdev) +{

• int ret;
• struct snd_soc_card *card;
• card = devm_kzalloc(&pdev->dev, sizeof(*card), GFP_KERNEL);
• if (!card)

• return -ENOMEM;
  

• card->dev = &pdev->dev;
• 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.