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    Subject[PATCH 5.10 21/98] dmaengine: of-dma: router_xlate to return -EPROBE_DEFER if controller is not yet available
    Date
    From: Peter Ujfalusi <peter.ujfalusi@gmail.com>

    [ Upstream commit eda97cb095f2958bbad55684a6ca3e7d7af0176a ]

    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>
    Link: https://lore.kernel.org/r/20210717190021.21897-1-peter.ujfalusi@gmail.com
    Signed-off-by: Vinod Koul <vkoul@kernel.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    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 8a4f608904b9..4be433482053 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)) {
    @@ -79,6 +83,7 @@ static struct dma_chan *of_dma_router_xlate(struct of_phandle_args *dma_spec,
    chan->route_data = route_data;
    }

    +err:
    /*
    * Need to put the node back since the ofdma->of_dma_route_allocate
    * has taken it for generating the new, translated dma_spec
    --
    2.30.2
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