Re: [PATCH RFC 4/4] mmc: host: renesas_sdhi_sys_dmac: Set dma_buswidth value to 32 byte

[Wolfram Sang <wsa@xxxxxxxxxxxxx>]

Hi Shimoda-san,

Interesting series!

> -	.dma_buswidth	= DMA_SLAVE_BUSWIDTH_4_BYTES,
> +	.dma_buswidth	= DMA_SLAVE_BUSWIDTH_32_BYTES,

Two very high level questions:

1) can't we set dma_priv->dma_buswidth at runtime when we know what the
card is capable of? Either DMA_SLAVE_BUSWIDTH_32_BYTES or
DMA_SLAVE_BUSWIDTH_4_BYTES? Then we don't need to fallback to PIO.
AFAIS, we only Gen2 sets .dma_buswidth in of_data, so we could even
remove it from of_data entirely?

2) Just by grepping in mmc/hosts, I see that no driver uses
DMA_SLAVE_BUSWIDTH_32_BYTES. Do you have an idea why? Because it is the
convenient setting which works for all cards?

Thanks and kind regards,

   Wolfram

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