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

Vinod Koul
2023-12-11T10:54:05Z

On 08-12-23, 14:49, Jan Kuliga wrote:
> 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);

Why this change, checkpatch would tell you this is not expected
alignment (run with strict)

> 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

--
~Vinod