Re: [PATCH v1 1/2] at_hdmac: check and return DMA_PAUSED status when suitable

Tudor.Ambarus
2022-11-08T11:50:32Z

Hi, Andy,

On 11/8/22 09:49, Andy Shevchenko wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>
> device_tx_status() may return DMA_PAUSED status when driver supports it.

Yeah, but you haven't described the why. And that's because dma_cookie_status()
currently considers just DMA_COMPLETE and DMA_IN_PROGRESS for the status of the
cookie, so the controller drivers are forced to query the DMA_PAUSED state
themselves.

Also, I noticed that Vinod prefers that you use the full paragraph in the commit
message, and not a continuation of the patch title, so you may want to reword
the commit message.

>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> ---
> drivers/dma/at_hdmac.c | 15 ++++++++++++++-
> 1 file changed, 14 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/dma/at_hdmac.c b/drivers/dma/at_hdmac.c
> index 8858470246e1..a9d8dd990d6e 100644
> --- a/drivers/dma/at_hdmac.c
> +++ b/drivers/dma/at_hdmac.c
> @@ -1669,9 +1669,19 @@ atc_tx_status(struct dma_chan *chan,
> int ret;
>
> dma_status = dma_cookie_status(chan, cookie, txstate);
> - if (dma_status == DMA_COMPLETE || !txstate)
> + if (dma_status == DMA_COMPLETE)
> return dma_status;
>
> + /*
> + * There's no point in calculating the residue if there's
> + * no txstate to store the value.
> + */
> + if (!txstate) {
> + if (test_bit(ATC_IS_PAUSED, &atchan->status))

there's a helper function that you can use instead: atc_chan_is_paused()

> + return DMA_PAUSED;
> + return DMA_ERROR;

return dma_status please

> + }
> +
> spin_lock_irqsave(&atchan->vc.lock, flags);
> /* Get number of bytes left in the active transactions */
> ret = atc_get_residue(chan, cookie, &residue);
> @@ -1684,6 +1694,9 @@ atc_tx_status(struct dma_chan *chan,
> dma_set_residue(txstate, residue);
> }
>
> + if (test_bit(ATC_IS_PAUSED, &atchan->status))

The status may change after spin_unlock_irqrestore(). Should the residue
be in sync with the dma status? If yes, you should check the status while
holding the lock.

> + dma_status = DMA_PAUSED;
> +
> dev_vdbg(chan2dev(chan), "tx_status %d: cookie = %d residue = %u\n",
> dma_status, cookie, residue);
>
> --
> 2.35.1
>

--
Cheers,
ta