On Fri, Jul 10, 2015 at 12:07:25PM +0200, Geert Uytterhoeven wrote: > If CONFIG_SH_DMAE_BASE (which is required for DMA engine support for > legacy SH, SH/R-Mobile, and R-Car Gen1, but not for R-Car Gen2) is not > enabled, but CONFIG_RCAR_DMAC (for R-Car Gen2 DMA engine support) is, > and the DTS doesn't provide a "dmas" property for a device, > dma_request_slave_channel_compat() incorrectly succeeds, and returns a > DMA channel. > > However, when trying to use that DMA channel later, it fails with: > > rcar-dmac e6700000.dma-controller: rcar_dmac_prep_slave_sg: bad parameter: len=1, id=-22 > > (Fortunately most drivers can handle this failure, and fall back to > PIO) > > The reason for this is that a NULL legacy filter function is used, which > actually means "all channels are OK", not "do not match". > If CONFIG_SH_DMAE_BASE is enabled (like in shmobile_defconfig, which > supports other SoCs besides R-Car Gen2), shdma_chan_filter() correctly > returns false, as no available channel on R-Car Gen2 matches a > shdma-base channel. > If the DTS does provide a "dmas" property, dma_request_slave_channel() > succeeds, and legacy filter-based matching is not used. > > To fix this, change shdma_chan_filter from being NULL to a dummy > function that always returns false, like is done on other platforms. Applied, thanks -- ~Vinod -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
