[PATCH AUTOSEL 4.9 3/8] dmaengine: of-dma: router_xlate to return -EPROBE_DEFER if controller is not yet available

From: Sasha Levin
Date: Tue Aug 10 2021 - 10:22:22 EST

From: Peter Ujfalusi <peter.ujfalusi@xxxxxxxxx>

[ 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@xxxxxxxxx>
Link: https://lore.kernel.org/r/20210717190021.21897-1-peter.ujfalusi@xxxxxxxxx
Signed-off-by: Vinod Koul <vkoul@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
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 757cf48c1c5e..441f37b41abd 100644
--- a/drivers/dma/of-dma.c
+++ b/drivers/dma/of-dma.c
@@ -68,8 +68,12 @@ 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);
+ goto err;
+ }

chan = ofdma_target->of_dma_xlate(&dma_spec_target, ofdma_target);
if (IS_ERR_OR_NULL(chan)) {
@@ -80,6 +84,7 @@ static struct dma_chan *of_dma_router_xlate(struct of_phandle_args *dma_spec,
chan->route_data = route_data;

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