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    Subject[PATCH] dmaengine: of-dma: router_xlate to return -EPROBE_DEFER if controller is not yet available
    Date
    If the router_xlate can not find the controller in the available DMA
    devices then it should return with -EPORBE_DEFER in a same way as the
    of_dma_request_slave_channel() does.

    The issue can be reproduced if the event router is registered before the
    DMA controller itself and a driver would request for a channel before the
    controller is registered.
    In of_dma_request_slave_channel():
    1. of_dma_find_controller() would find the dma_router
    2. ofdma->of_dma_xlate() would fail and returned NULL
    3. -ENODEV is returned as error code

    with this patch we would return in this case the correct -EPROBE_DEFER and
    the client can try to request the channel later.

    Signed-off-by: Peter Ujfalusi <peter.ujfalusi@gmail.com>
    ---
    Hi,

    I have noticed the descibed failure sequence on Beagle-x15 board (McASP fails to
    probe). It must have been broken for some time, I have not booted the board for
    about a year or so...

    Regards,
    Peter

    drivers/dma/of-dma.c | 9 +++++++--
    1 file changed, 7 insertions(+), 2 deletions(-)

    diff --git a/drivers/dma/of-dma.c b/drivers/dma/of-dma.c
    index ec00b20ae8e4..ac61ecda2926 100644
    --- a/drivers/dma/of-dma.c
    +++ b/drivers/dma/of-dma.c
    @@ -67,8 +67,12 @@ static struct dma_chan *of_dma_router_xlate(struct of_phandle_args *dma_spec,
    return NULL;

    ofdma_target = of_dma_find_controller(&dma_spec_target);
    - if (!ofdma_target)
    - return NULL;
    + if (!ofdma_target) {
    + ofdma->dma_router->route_free(ofdma->dma_router->dev,
    + route_data);
    + chan = ERR_PTR(-EPROBE_DEFER);
    + goto err;
    + }

    chan = ofdma_target->of_dma_xlate(&dma_spec_target, ofdma_target);
    if (IS_ERR_OR_NULL(chan)) {
    @@ -89,6 +93,7 @@ static struct dma_chan *of_dma_router_xlate(struct of_phandle_args *dma_spec,
    }
    }

    +err:
    /*
    * Need to put the node back since the ofdma->of_dma_route_allocate
    * has taken it for generating the new, translated dma_spec
    --
    2.32.0
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