dmaengine: virt-dma: Add missing locking

Originally freeing descriptors was split into a locked and an unlocked
part. The locked part in vchan_get_all_descriptors() collected all
descriptors on a separate list_head. This was done to allow iterating
over that new list in vchan_dma_desc_free_list() without a lock held.

This became broken in 13bb26ae8850 ("dmaengine: virt-dma: don't always
free descriptor upon completion"). With this commit
vchan_dma_desc_free_list() no longer exclusively operates on the
separate list, but starts to put descriptors which can be reused back on
&vc->desc_allocated. This list operation should have been locked, but
wasn't.
In the mean time drivers started to call vchan_dma_desc_free_list() with
their lock held so that we now have the situation that
vchan_dma_desc_free_list() is called locked from some drivers and
unlocked from others.
To clean this up we have to do two things:

1. Add missing locking in vchan_dma_desc_free_list()
2. Make sure drivers call vchan_dma_desc_free_list() unlocked

This needs to be done atomically, so in this patch the locking is added
and all drivers are fixed.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Reviewed-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Tested-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Reviewed-by: Green Wan <green.wan@sifive.com>
Tested-by: Green Wan <green.wan@sifive.com>
Link: https://lore.kernel.org/r/20191216105328.15198-3-s.hauer@pengutronix.de
Signed-off-by: Vinod Koul <vkoul@kernel.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/drivers/dma/owl-dma.c b/drivers/dma/owl-dma.c
index 023f951189a7..c683051257fd 100644
--- a/drivers/dma/owl-dma.c
+++ b/drivers/dma/owl-dma.c
@@ -674,10 +674,11 @@ static int owl_dma_terminate_all(struct dma_chan *chan)
 	}
 
 	vchan_get_all_descriptors(&vchan->vc, &head);
-	vchan_dma_desc_free_list(&vchan->vc, &head);
 
 	spin_unlock_irqrestore(&vchan->vc.lock, flags);
 
+	vchan_dma_desc_free_list(&vchan->vc, &head);
+
 	return 0;
 }