[PATCH v4 4/8] dmaengine: xilinx: xdma: Rework xdma_terminate_all()

Jan Kuliga
2023-12-08T13:50:24Z

Simplify xdma_xfer_stop(). Stop the dma engine and clear its status
register unconditionally - just do what its name states. This change
also allows to call it without grabbing a lock, which minimizes
the total time spent with a spinlock held.

Delete the currently processed vd.node from the vc.desc_issued list
prior to passing it to vchan_terminate_vdesc(). In case there's more
than one descriptor pending on vc.desc_issued list, calling
vchan_terminate_desc() results in losing the link between
vc.desc_issued list head and the second descriptor on the list. Doing so
results in resources leakege, as vchan_dma_desc_free_list() won't be
able to properly free memory resources attached to descriptors,
resulting in dma_pool_destroy() failure.

Don't call vchan_dma_desc_free_list() from within xdma_terminate_all().
Move all terminated descriptors to the vc.desc_terminated list instead.
This allows to postpone freeing memory resources associated with
descriptors until the call to vchan_synchronize(), which is called from
xdma_synchronize() callback. This is the right way to do it -
xdma_terminate_all() should return as soon as possible, while freeing
resources (that may be time consuming in case of large number of
descriptors) can be done safely later.

Fixes: 290bb5d2d1e2
("dmaengine: xilinx: xdma: Add terminate_all/synchronize callbacks")

Signed-off-by: Jan Kuliga <jankul@alatek.krakow.pl>
---
drivers/dma/xilinx/xdma.c | 32 ++++++++++++++++----------------
1 file changed, 16 insertions(+), 16 deletions(-)

diff --git a/drivers/dma/xilinx/xdma.c b/drivers/dma/xilinx/xdma.c
index 1bce48e5d86c..521ba2a653b6 100644
--- a/drivers/dma/xilinx/xdma.c
+++ b/drivers/dma/xilinx/xdma.c
@@ -379,20 +379,20 @@ static int xdma_xfer_start(struct xdma_chan *xchan)
*/
static int xdma_xfer_stop(struct xdma_chan *xchan)
{
- struct virt_dma_desc *vd = vchan_next_desc(&xchan->vchan);
- struct xdma_device *xdev = xchan->xdev_hdl;
int ret;
-
- if (!vd || !xchan->busy)
- return -EINVAL;
+ u32 val;
+ struct xdma_device *xdev = xchan->xdev_hdl;

/* clear run stop bit to prevent any further auto-triggering */
ret = regmap_write(xdev->rmap, xchan->base + XDMA_CHAN_CONTROL_W1C,
- CHAN_CTRL_RUN_STOP);
+ CHAN_CTRL_RUN_STOP);
if (ret)
return ret;

- xchan->busy = false;
+ /* Clear the channel status register */
+ ret = regmap_read(xdev->rmap, xchan->base + XDMA_CHAN_STATUS_RC, &val);
+ if (ret)
+ return ret;

return 0;
}
@@ -505,25 +505,25 @@ static void xdma_issue_pending(struct dma_chan *chan)
static int xdma_terminate_all(struct dma_chan *chan)
{
struct xdma_chan *xdma_chan = to_xdma_chan(chan);
- struct xdma_desc *desc = NULL;
struct virt_dma_desc *vd;
unsigned long flags;
LIST_HEAD(head);

- spin_lock_irqsave(&xdma_chan->vchan.lock, flags);
xdma_xfer_stop(xdma_chan);

+ spin_lock_irqsave(&xdma_chan->vchan.lock, flags);
+
+ xdma_chan->busy = false;
vd = vchan_next_desc(&xdma_chan->vchan);
- if (vd)
- desc = to_xdma_desc(vd);
- if (desc) {
- dma_cookie_complete(&desc->vdesc.tx);
- vchan_terminate_vdesc(&desc->vdesc);
+ if (vd) {
+ list_del(&vd->node);
+ dma_cookie_complete(&vd->tx);
+ vchan_terminate_vdesc(vd);
}
-
vchan_get_all_descriptors(&xdma_chan->vchan, &head);
+ list_splice_tail(&head, &xdma_chan->vchan.desc_terminated);
+
spin_unlock_irqrestore(&xdma_chan->vchan.lock, flags);
- vchan_dma_desc_free_list(&xdma_chan->vchan, &head);

return 0;
}
--
2.34.1