[PATCH 2/2] dma: tegra: avoid channel lock up after free

[Dmitry Osipenko <digetx-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

Lock scenario: Channel 1 was allocated and prepared as slave_sg, used and freed.
Now preparation of cyclic dma on channel 1 will fail with err "DMA configuration
conflict" because tdc->isr_handler still setted to handle_once_dma_done.

This happens because tegra_dma_abort_all() won't be called on channel freeing
if pending list is empty and channel not busy. We need to clear isr_handler
on channel freeing to avoid locking.

Signed-off-by: Dmitry Osipenko <digetx-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
---
I have sent this fix some month ago and Laxman gave his ack, but since that
time I found that it's not right to include multiple changes in one patch,
so converted it to trivial change.

 drivers/dma/tegra20-apb-dma.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/dma/tegra20-apb-dma.c b/drivers/dma/tegra20-apb-dma.c
index a84bb7f..c541276 100644
--- a/drivers/dma/tegra20-apb-dma.c
+++ b/drivers/dma/tegra20-apb-dma.c
@@ -1191,6 +1191,7 @@ static void tegra_dma_free_chan_resources(struct dma_chan *dc)
 	list_splice_init(&tdc->free_dma_desc, &dma_desc_list);
 	INIT_LIST_HEAD(&tdc->cb_desc);
 	tdc->config_init = false;
+	tdc->isr_handler = NULL;
 	spin_unlock_irqrestore(&tdc->lock, flags);
 
 	while (!list_empty(&dma_desc_list)) {
-- 
1.8.2.1