Re: [PATCH] mci: dw_mmc: set dma mask to work correctly on 64bit platforms

[Sascha Hauer <s.hauer@pengutronix.de>]

On Fri, Jun 11, 2021 at 10:23:25AM +0200, Ahmad Fatoum wrote:
> Hello Sascha,
> 
> On 10.06.21 15:10, Sascha Hauer wrote:
> > The variant we support currently can only do 32bit DMA. Adjust dma mask
> > accordingly. Also use dma_map_single() rather than dma_sync_single() to
> > actually get errors when the mapping fails.
> > 
> > Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> 
> Tested-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
> 
> On a StarFive JH7100 (64-bit CPU, 32-bit MMC controller, non-1:1 mapping for
> coherent DMA).
> 
> >  	host->idmac = dma_alloc_coherent(sizeof(*host->idmac) * DW_MMC_NUM_IDMACS,
> > -					 DMA_ADDRESS_BROKEN);
> > +					 &host->idmac_dma);
> > +	if (!host->idmac)
> 
> That works for Linux, but not for barebox: barebox dma_alloc_coherent doesn't have
> 
> a dev parameter, so it can't check for dma_mapping_error() internally.

Yeah, I know. I have that on my mental todo list and hoped nobody would
realize.
Adding a dev parameter to dma_alloc_coherent() is one thing. With that
we can check for errors. The next step of course would be to allocate
memory in the allowed area, not only to complain.

> 
> dma_alloc_coherent also never returns NULL in barebox, all implementations, except
> 
> for kvx, abort if no memory could be allocated.
> 
> > +		return PTR_ERR(-ENOMEM);
> 
> -ENOMEM is no pointer.

Yes, fixed.

Sascha

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