From eda97cb095f2958bbad55684a6ca3e7d7af0176a Mon Sep 17 00:00:00 2001
From: Peter Ujfalusi <peter.ujfalusi@gmail.com>
Date: Sat, 17 Jul 2021 22:00:21 +0300
Subject: [PATCH] dmaengine: of-dma: router_xlate to return -EPROBE_DEFER if controller is not yet available
Git-commit: eda97cb095f2958bbad55684a6ca3e7d7af0176a
Patch-mainline: v5.14-rc5
References: git-fixes

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>
Acked-by: Takashi Iwai <tiwai@suse.de>

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

--- a/drivers/dma/of-dma.c
+++ b/drivers/dma/of-dma.c
@@ -65,8 +65,12 @@ static struct dma_chan *of_dma_router_xl
 		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)) {
@@ -77,6 +81,7 @@ static struct dma_chan *of_dma_router_xl
 		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