imx7: dev->coherent_dma_mask NULL warning

[Christoph Hellwig]

On Tue, Aug 17, 2021 at 09:23:26PM -0300, Fabio Estevam wrote:
> 
> void *dma_alloc_attrs(struct device *dev, size_t size, dma_addr_t *dma_handle,
> ....
> WARN_ON_ONCE(!dev->coherent_dma_mask);
> 
> Where should the coherent_dma_mask be set to avoid this problem?

Looking at the ath10k code ar->dev is set by ath10k_core_create, which
has multiple callers.

For ath10k_pci_probe it is a pci_dev, whoch should always have a
dma_mask.
For ath10k_ahb_probe is is a device tree probed platform_device,
which should have a dma mask.
For ath10k_sdio_probe it is a sdio_func, which from my understanding is
a virtual device can't do DMA itself.
For ath10k_snoc_probe it is a platform device wit an explicit
dma_set_mask_and_coherent and above so the dma_mask is set.
For ath10k_usb_probe it is an usb device which can't do USB

So unless I misred the driver you're using the SDIO or USB variant,
and those are not allowed to just call dma_* functions on their
respective devices.