• Geert Uytterhoeven's avatar
    dmaengine: shdma: Make dummy shdma_chan_filter() always return false · 056f6c87
    Geert Uytterhoeven authored
    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.
    Signed-off-by: default avatarGeert Uytterhoeven <geert+renesas@glider.be>
    Signed-off-by: default avatarVinod Koul <vinod.koul@intel.com>
    056f6c87
shdma-base.h 4.41 KB