Hi Shimoda-san, > > 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? > > As I replied to Ulrich-san on other email thread, for now, rcar-dmac has a limitation > on dmaengine_slave_config(), we should not call it at runtime. But, I don't think > any sd card have such a limitation. In other words, if rcar-dmac doesn't have > the limitation, I think we can change the buswidth at runtime and then we can > remove the .dma_buswidth from of_data. So, that I understand correctly: The DMAC limitation is because of the driver and not because of the HW? If so, is it hard/planned to be fixed? > I also grepped in drivers/dma, and all dmaengine drivers except Renesas related > SoCs don't support DMA_SLAVE_BUSWIDTH_32_BYTES. So, I think no driver uses > the 32 bytes on mmc/hosts :) Wow, we are bleeding edge with this? :) Thanks, Wolfram
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