Re: [PATCH 21/22] mmc: wbsd: Use dma_alloc_noncoherent() for dma buffer

Baoquan He
2022-02-22T09:14:42Z

On 02/22/22 at 09:45am, Christoph Hellwig wrote:
> On Sun, Feb 20, 2022 at 04:40:44PM +0800, Baoquan He wrote:
> > On 02/19/22 at 08:17am, Christoph Hellwig wrote:
> > > On Sat, Feb 19, 2022 at 08:52:20AM +0800, Baoquan He wrote:
> > > > if (request_dma(dma, DRIVER_NAME))
> > > > goto err;
> > > >
> > > > + dma_set_mask_and_coherent(mmc_dev(host->mmc), DMA_BIT_MASK(24));
> > >
> > > This also sets the streaming mask, but the driver doesn't seem to make
> > > use of that. Please document it in the commit log.
> >
> > Thanks for reviewing. I will change it to dma_set_mask(), and describe
> > this change in patch log.
>
> No, if you change it, it should be dma_set_coherent_mask only as it is
> not using streaming mappings. I suspect dma_set_mask_and_coherent is
> the right thing if the driver ever wants to use streaming mapping,
> it would just need to be documented in the commit message.

It will serve dma_alloc_noncoherent() calling later, should be streaming
mapping?