Re: [PATCH 1/3] dmaengine: dw-edma: Implement device_synchronize() callback

On Mon, Jun 29, 2026 at 10:45:15AM +0200, Manivannan Sadhasivam via B4 Relay wrote:
>
> From: Manivannan Sadhasivam <[email protected]>
>
> device_synchronize() callback is required by the client drivers to ensure
> all the DMA operations are completed so that they can free the memory
> associated with the complete callbacks.
>
> So implement this callback by first making sure that all the in-flight DMA
> operations are completed and then call vchan_synchronize() to drain the
> DMA tasklet.
>
> Signed-off-by: Manivannan Sadhasivam <[email protected]>
> ---
>  drivers/dma/dw-edma/dw-edma-core.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
>
> diff --git a/drivers/dma/dw-edma/dw-edma-core.c b/drivers/dma/dw-edma/dw-edma-core.c
> index c2feb3adc79f..7b12dfe8cfd3 100644
> --- a/drivers/dma/dw-edma/dw-edma-core.c
> +++ b/drivers/dma/dw-edma/dw-edma-core.c
> @@ -331,6 +331,21 @@ static int dw_edma_device_terminate_all(struct dma_chan *dchan)
>         return err;
>  }
>
> +static void dw_edma_device_synchronize(struct dma_chan *dchan)
> +{
> +       struct dw_edma_chan *chan = dchan2dw_edma_chan(dchan);
> +       unsigned long timeout = jiffies + msecs_to_jiffies(5000);
> +
> +       /*
> +        * Make sure all the in-flight DMA operations are completed before
> +        * draining the tasklet using vchan_synchronize().
> +        */
> +       while (chan->status == EDMA_ST_BUSY && time_before(jiffies, timeout))
> +               cpu_relax();

read_poll_timeout(...),  Does need READ_ONCE(chan->status)?

Frank

> +
> +       vchan_synchronize(&chan->vc);
> +}
> +
>  static void dw_edma_device_issue_pending(struct dma_chan *dchan)
>  {
>         struct dw_edma_chan *chan = dchan2dw_edma_chan(dchan);
> @@ -968,6 +983,7 @@ static int dw_edma_channel_setup(struct dw_edma *dw, u32 wr_alloc, u32 rd_alloc)
>         dma->device_pause = dw_edma_device_pause;
>         dma->device_resume = dw_edma_device_resume;
>         dma->device_terminate_all = dw_edma_device_terminate_all;
> +       dma->device_synchronize = dw_edma_device_synchronize;
>         dma->device_issue_pending = dw_edma_device_issue_pending;
>         dma->device_tx_status = dw_edma_device_tx_status;
>         dma->device_prep_slave_sg = dw_edma_device_prep_slave_sg;
>
> --
> 2.43.0
>
>