2021-07-17 18:59:39

by Péter Ujfalusi

Subject: [PATCH] dmaengine: of-dma: router_xlate to return -EPROBE_DEFER if controller is not yet available

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 <[email protected]>
---
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

2021-07-28 07:13:19

by Vinod Koul

Subject: Re: [PATCH] dmaengine: of-dma: router_xlate to return -EPROBE_DEFER if controller is not yet available

On 17-07-21, 22:00, Peter Ujfalusi wrote:
> 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.

Applied, thanks

--
~Vinod