diff mbox series

dmaengine: pl330: Return DMA_PAUSED when transaction is paused

Message ID 20230526105434.14959-1-ilpo.jarvinen@linux.intel.com
State New
Headers show
Series dmaengine: pl330: Return DMA_PAUSED when transaction is paused | expand

Commit Message

Ilpo Järvinen May 26, 2023, 10:54 a.m. UTC
pl330_pause() does not set anything to indicate paused condition which
causes pl330_tx_status() to return DMA_IN_PROGRESS. This breaks 8250
DMA flush after the fix in commit 57e9af7831dc ("serial: 8250_dma: Fix
DMA Rx rearm race"). The function comment for pl330_pause() claims
pause is supported but resume is not which is enough for 8250 DMA flush
to work as long as DMA status reports DMA_PAUSED when appropriate.

Add PAUSED state for descriptor and mark BUSY descriptors with PAUSED
in pl330_pause(). Return DMA_PAUSED from pl330_tx_status() when the
descriptor is PAUSED.

Reported-by: Richard Tresidder <rtresidd@electromag.com.au>
Tested-by: Richard Tresidder <rtresidd@electromag.com.au>
Fixes: 88987d2c7534 ("dmaengine: pl330: add DMA_PAUSE feature")
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/linux-serial/f8a86ecd-64b1-573f-c2fa-59f541083f1a@electromag.com.au/
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
---

$ diff -u <(git grep -l -e '\.device_pause' -e '->device_pause') <(git grep -l DMA_PAUSED)

...tells there might a few other drivers which do not properly return
DMA_PAUSED status despite having a pause function.

 drivers/dma/pl330.c | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

Comments

Thorsten Leemhuis June 26, 2023, 11:50 a.m. UTC | #1
On 26.05.23 12:54, Ilpo Järvinen wrote:
> pl330_pause() does not set anything to indicate paused condition which
> causes pl330_tx_status() to return DMA_IN_PROGRESS. This breaks 8250
> DMA flush after the fix in commit 57e9af7831dc ("serial: 8250_dma: Fix
> DMA Rx rearm race"). The function comment for pl330_pause() claims
> pause is supported but resume is not which is enough for 8250 DMA flush
> to work as long as DMA status reports DMA_PAUSED when appropriate.
> 
> Add PAUSED state for descriptor and mark BUSY descriptors with PAUSED
> in pl330_pause(). Return DMA_PAUSED from pl330_tx_status() when the
> descriptor is PAUSED.
> 
> Reported-by: Richard Tresidder <rtresidd@electromag.com.au>
> Tested-by: Richard Tresidder <rtresidd@electromag.com.au>
> Fixes: 88987d2c7534 ("dmaengine: pl330: add DMA_PAUSE feature")
> Cc: stable@vger.kernel.org
> Link: https://lore.kernel.org/linux-serial/f8a86ecd-64b1-573f-c2fa-59f541083f1a@electromag.com.au/
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

Ilpo, Vinod, Philipp: what happened to this? It seems this fix for a
regression didn't make any progress since it was posted. Or am I missing
something?

Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)
--
Everything you wanna know about Linux kernel regression tracking:
https://linux-regtracking.leemhuis.info/about/#tldr
If I did something stupid, please tell me, as explained on that page.

> ---
> 
> $ diff -u <(git grep -l -e '\.device_pause' -e '->device_pause') <(git grep -l DMA_PAUSED)
> 
> ...tells there might a few other drivers which do not properly return
> DMA_PAUSED status despite having a pause function.
> 
>  drivers/dma/pl330.c | 18 ++++++++++++++++--
>  1 file changed, 16 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c
> index 0d9257fbdfb0..daad25f2c498 100644
> --- a/drivers/dma/pl330.c
> +++ b/drivers/dma/pl330.c
> @@ -403,6 +403,12 @@ enum desc_status {
>  	 * of a channel can be BUSY at any time.
>  	 */
>  	BUSY,
> +	/*
> +	 * Pause was called while descriptor was BUSY. Due to hardware
> +	 * limitations, only termination is possible for descriptors
> +	 * that have been paused.
> +	 */
> +	PAUSED,
>  	/*
>  	 * Sitting on the channel work_list but xfer done
>  	 * by PL330 core
> @@ -2041,7 +2047,7 @@ static inline void fill_queue(struct dma_pl330_chan *pch)
>  	list_for_each_entry(desc, &pch->work_list, node) {
>  
>  		/* If already submitted */
> -		if (desc->status == BUSY)
> +		if (desc->status == BUSY || desc->status == PAUSED)
>  			continue;
>  
>  		ret = pl330_submit_req(pch->thread, desc);
> @@ -2326,6 +2332,7 @@ static int pl330_pause(struct dma_chan *chan)
>  {
>  	struct dma_pl330_chan *pch = to_pchan(chan);
>  	struct pl330_dmac *pl330 = pch->dmac;
> +	struct dma_pl330_desc *desc;
>  	unsigned long flags;
>  
>  	pm_runtime_get_sync(pl330->ddma.dev);
> @@ -2335,6 +2342,10 @@ static int pl330_pause(struct dma_chan *chan)
>  	_stop(pch->thread);
>  	spin_unlock(&pl330->lock);
>  
> +	list_for_each_entry(desc, &pch->work_list, node) {
> +		if (desc->status == BUSY)
> +			desc->status = PAUSED;
> +	}
>  	spin_unlock_irqrestore(&pch->lock, flags);
>  	pm_runtime_mark_last_busy(pl330->ddma.dev);
>  	pm_runtime_put_autosuspend(pl330->ddma.dev);
> @@ -2425,7 +2436,7 @@ pl330_tx_status(struct dma_chan *chan, dma_cookie_t cookie,
>  		else if (running && desc == running)
>  			transferred =
>  				pl330_get_current_xferred_count(pch, desc);
> -		else if (desc->status == BUSY)
> +		else if (desc->status == BUSY || desc->status == PAUSED)
>  			/*
>  			 * Busy but not running means either just enqueued,
>  			 * or finished and not yet marked done
> @@ -2442,6 +2453,9 @@ pl330_tx_status(struct dma_chan *chan, dma_cookie_t cookie,
>  			case DONE:
>  				ret = DMA_COMPLETE;
>  				break;
> +			case PAUSED:
> +				ret = DMA_PAUSED;
> +				break;
>  			case PREP:
>  			case BUSY:
>  				ret = DMA_IN_PROGRESS;
Vinod Koul Aug. 1, 2023, 6:44 p.m. UTC | #2
On Fri, 26 May 2023 13:54:34 +0300, Ilpo Järvinen wrote:
> pl330_pause() does not set anything to indicate paused condition which
> causes pl330_tx_status() to return DMA_IN_PROGRESS. This breaks 8250
> DMA flush after the fix in commit 57e9af7831dc ("serial: 8250_dma: Fix
> DMA Rx rearm race"). The function comment for pl330_pause() claims
> pause is supported but resume is not which is enough for 8250 DMA flush
> to work as long as DMA status reports DMA_PAUSED when appropriate.
> 
> [...]

Applied, thanks!

[1/1] dmaengine: pl330: Return DMA_PAUSED when transaction is paused
      commit: 85648667b946069b2a3765577c418705c65c2ddf

Best regards,
diff mbox series

Patch

diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c
index 0d9257fbdfb0..daad25f2c498 100644
--- a/drivers/dma/pl330.c
+++ b/drivers/dma/pl330.c
@@ -403,6 +403,12 @@  enum desc_status {
 	 * of a channel can be BUSY at any time.
 	 */
 	BUSY,
+	/*
+	 * Pause was called while descriptor was BUSY. Due to hardware
+	 * limitations, only termination is possible for descriptors
+	 * that have been paused.
+	 */
+	PAUSED,
 	/*
 	 * Sitting on the channel work_list but xfer done
 	 * by PL330 core
@@ -2041,7 +2047,7 @@  static inline void fill_queue(struct dma_pl330_chan *pch)
 	list_for_each_entry(desc, &pch->work_list, node) {
 
 		/* If already submitted */
-		if (desc->status == BUSY)
+		if (desc->status == BUSY || desc->status == PAUSED)
 			continue;
 
 		ret = pl330_submit_req(pch->thread, desc);
@@ -2326,6 +2332,7 @@  static int pl330_pause(struct dma_chan *chan)
 {
 	struct dma_pl330_chan *pch = to_pchan(chan);
 	struct pl330_dmac *pl330 = pch->dmac;
+	struct dma_pl330_desc *desc;
 	unsigned long flags;
 
 	pm_runtime_get_sync(pl330->ddma.dev);
@@ -2335,6 +2342,10 @@  static int pl330_pause(struct dma_chan *chan)
 	_stop(pch->thread);
 	spin_unlock(&pl330->lock);
 
+	list_for_each_entry(desc, &pch->work_list, node) {
+		if (desc->status == BUSY)
+			desc->status = PAUSED;
+	}
 	spin_unlock_irqrestore(&pch->lock, flags);
 	pm_runtime_mark_last_busy(pl330->ddma.dev);
 	pm_runtime_put_autosuspend(pl330->ddma.dev);
@@ -2425,7 +2436,7 @@  pl330_tx_status(struct dma_chan *chan, dma_cookie_t cookie,
 		else if (running && desc == running)
 			transferred =
 				pl330_get_current_xferred_count(pch, desc);
-		else if (desc->status == BUSY)
+		else if (desc->status == BUSY || desc->status == PAUSED)
 			/*
 			 * Busy but not running means either just enqueued,
 			 * or finished and not yet marked done
@@ -2442,6 +2453,9 @@  pl330_tx_status(struct dma_chan *chan, dma_cookie_t cookie,
 			case DONE:
 				ret = DMA_COMPLETE;
 				break;
+			case PAUSED:
+				ret = DMA_PAUSED;
+				break;
 			case PREP:
 			case BUSY:
 				ret = DMA_IN_PROGRESS;