[PATCH 0/1] dmaengine: imx-sdma - fix the dma residue calculation

[PATCH 0/1] dmaengine: imx-sdma - fix the dma residue calculation

[Nandor Han]

The patch will correct the calculation of the dma residue taking in consideration
that some subsystem can check the dma status without waiting the dma complete event.

Affected devices: imx based device using sdma module with cyclic channels.

Tested on imx6 and imx53 by playing wav files using `speaker-test`application, part
of alsa-utils package, and verify that the sound plays smoothly without interruptions. 
Verified also the serial communication by transferring data over the serial line using
various packet sizes and checked the logs and the serial port status
(`cat /proc/tty/driver/IMX-uart`) that no data is lost.

Nandor Han (1):
  dmaengine: imx-sdma - correct the dma transfer residue calculation

 drivers/dma/imx-sdma.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

-- 
2.7.1

[PATCH 1/1] dmaengine: imx-sdma - correct the dma transfer residue calculation

[Nandor Han]

The residue calculation was taking in consideration that dma
transaction status will be always retrieved in the dma callback
used to inform that dma transfer is complete. However this is not
the case for all subsystems that use dma. Some subsystems use a
timer to check the dma status periodically.

Therefore the calculation was updated and residue is calculated
accordingly by a) update the residue calculation taking in
consideration the last used buffer index by using *buf_ptail* variable
and b) chn_real_count (number of bytes transferred) is initialized to
zero, when dma channel is created, to avoid using an uninitialized
value in residue calculation when dma status is checked without
waiting dma complete event.

Signed-off-by: Nandor Han <nandor.han@ge.com>
---
 drivers/dma/imx-sdma.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c
index b9629b2..d1651a5 100644
--- a/drivers/dma/imx-sdma.c
+++ b/drivers/dma/imx-sdma.c
@@ -298,6 +298,7 @@ struct sdma_engine;
  * @event_id1		for channels that use 2 events
  * @word_size		peripheral access size
  * @buf_tail		ID of the buffer that was processed
+ * @buf_ptail		ID of the previous buffer that was processed
  * @num_bd		max NUM_BD. number of descriptors currently handling
  */
 struct sdma_channel {
@@ -309,6 +310,7 @@ struct sdma_channel {
 	unsigned int			event_id1;
 	enum dma_slave_buswidth		word_size;
 	unsigned int			buf_tail;
+	unsigned int			buf_ptail;
 	unsigned int			num_bd;
 	unsigned int			period_len;
 	struct sdma_buffer_descriptor	*bd;
@@ -700,6 +702,8 @@ static void sdma_update_channel_loop(struct sdma_channel *sdmac)
 		sdmac->chn_real_count = bd->mode.count;
 		bd->mode.status |= BD_DONE;
 		bd->mode.count = sdmac->period_len;
+		sdmac->buf_ptail = sdmac->buf_tail;
+		sdmac->buf_tail = (sdmac->buf_tail + 1) % sdmac->num_bd;
 
 		/*
 		 * The callback is called from the interrupt context in order
@@ -710,9 +714,6 @@ static void sdma_update_channel_loop(struct sdma_channel *sdmac)
 
 		dmaengine_desc_get_callback_invoke(&sdmac->desc, NULL);
 
-		sdmac->buf_tail++;
-		sdmac->buf_tail %= sdmac->num_bd;
-
 		if (error)
 			sdmac->status = old_status;
 	}
@@ -1186,6 +1187,8 @@ static struct dma_async_tx_descriptor *sdma_prep_slave_sg(
 	sdmac->flags = 0;
 
 	sdmac->buf_tail = 0;
+	sdmac->buf_ptail = 0;
+	sdmac->chn_real_count = 0;
 
 	dev_dbg(sdma->dev, "setting up %d entries for channel %d.\n",
 			sg_len, channel);
@@ -1288,6 +1291,8 @@ static struct dma_async_tx_descriptor *sdma_prep_dma_cyclic(
 	sdmac->status = DMA_IN_PROGRESS;
 
 	sdmac->buf_tail = 0;
+	sdmac->buf_ptail = 0;
+	sdmac->chn_real_count = 0;
 	sdmac->period_len = period_len;
 
 	sdmac->flags |= IMX_DMA_SG_LOOP;
@@ -1385,7 +1390,7 @@ static enum dma_status sdma_tx_status(struct dma_chan *chan,
 	u32 residue;
 
 	if (sdmac->flags & IMX_DMA_SG_LOOP)
-		residue = (sdmac->num_bd - sdmac->buf_tail) *
+		residue = (sdmac->num_bd - sdmac->buf_ptail) *
 			   sdmac->period_len - sdmac->chn_real_count;
 	else
 		residue = sdmac->chn_count - sdmac->chn_real_count;
-- 
2.7.1

Re: [PATCH 1/1] dmaengine: imx-sdma - correct the dma transfer residue calculation

[Peter Senna Tschudin]

 
On Tuesday, October 11, 2016 13:13 CEST, Nandor Han <nandor.han@ge.com> wrote: 
 
> The residue calculation was taking in consideration that dma
> transaction status will be always retrieved in the dma callback
> used to inform that dma transfer is complete. However this is not
> the case for all subsystems that use dma. Some subsystems use a
> timer to check the dma status periodically.
> 
> Therefore the calculation was updated and residue is calculated
> accordingly by a) update the residue calculation taking in
> consideration the last used buffer index by using *buf_ptail* variable
> and b) chn_real_count (number of bytes transferred) is initialized to
> zero, when dma channel is created, to avoid using an uninitialized
> value in residue calculation when dma status is checked without
> waiting dma complete event.

The previous patch* apparently introduced an issue that was detectable when using the fsl_ssi audio driver that produced non smooth audio output. This patch fix the issue.

I tested this patch by booting it in two different devices and checked that the sound issues related to fsl_ssi driver were fixed.

* - https://patchwork.kernel.org/patch/9268463/

> 
> Signed-off-by: Nandor Han <nandor.han@ge.com>
Acked-by: Peter Senna Tschudin <peter.senna@collabora.com>
Tested-by: Peter Senna Tschudin <peter.senna@collabora.com>

> ---
>  drivers/dma/imx-sdma.c | 13 +++++++++----
>  1 file changed, 9 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c
> index b9629b2..d1651a5 100644
> --- a/drivers/dma/imx-sdma.c
> +++ b/drivers/dma/imx-sdma.c
> @@ -298,6 +298,7 @@ struct sdma_engine;
>   * @event_id1		for channels that use 2 events
>   * @word_size		peripheral access size
>   * @buf_tail		ID of the buffer that was processed
> + * @buf_ptail		ID of the previous buffer that was processed
>   * @num_bd		max NUM_BD. number of descriptors currently handling
>   */
>  struct sdma_channel {
> @@ -309,6 +310,7 @@ struct sdma_channel {
>  	unsigned int			event_id1;
>  	enum dma_slave_buswidth		word_size;
>  	unsigned int			buf_tail;
> +	unsigned int			buf_ptail;
>  	unsigned int			num_bd;
>  	unsigned int			period_len;
>  	struct sdma_buffer_descriptor	*bd;
> @@ -700,6 +702,8 @@ static void sdma_update_channel_loop(struct sdma_channel *sdmac)
>  		sdmac->chn_real_count = bd->mode.count;
>  		bd->mode.status |= BD_DONE;
>  		bd->mode.count = sdmac->period_len;
> +		sdmac->buf_ptail = sdmac->buf_tail;
> +		sdmac->buf_tail = (sdmac->buf_tail + 1) % sdmac->num_bd;
>  
>  		/*
>  		 * The callback is called from the interrupt context in order
> @@ -710,9 +714,6 @@ static void sdma_update_channel_loop(struct sdma_channel *sdmac)
>  
>  		dmaengine_desc_get_callback_invoke(&sdmac->desc, NULL);
>  
> -		sdmac->buf_tail++;
> -		sdmac->buf_tail %= sdmac->num_bd;
> -
>  		if (error)
>  			sdmac->status = old_status;
>  	}
> @@ -1186,6 +1187,8 @@ static struct dma_async_tx_descriptor *sdma_prep_slave_sg(
>  	sdmac->flags = 0;
>  
>  	sdmac->buf_tail = 0;
> +	sdmac->buf_ptail = 0;
> +	sdmac->chn_real_count = 0;
>  
>  	dev_dbg(sdma->dev, "setting up %d entries for channel %d.\n",
>  			sg_len, channel);
> @@ -1288,6 +1291,8 @@ static struct dma_async_tx_descriptor *sdma_prep_dma_cyclic(
>  	sdmac->status = DMA_IN_PROGRESS;
>  
>  	sdmac->buf_tail = 0;
> +	sdmac->buf_ptail = 0;
> +	sdmac->chn_real_count = 0;
>  	sdmac->period_len = period_len;
>  
>  	sdmac->flags |= IMX_DMA_SG_LOOP;
> @@ -1385,7 +1390,7 @@ static enum dma_status sdma_tx_status(struct dma_chan *chan,
>  	u32 residue;
>  
>  	if (sdmac->flags & IMX_DMA_SG_LOOP)
> -		residue = (sdmac->num_bd - sdmac->buf_tail) *
> +		residue = (sdmac->num_bd - sdmac->buf_ptail) *
>  			   sdmac->period_len - sdmac->chn_real_count;
>  	else
>  		residue = sdmac->chn_count - sdmac->chn_real_count;
> -- 
> 2.7.1
> 
 
 
 
 

Re: [PATCH 1/1] dmaengine: imx-sdma - correct the dma transfer residue calculation

[Marek Vasut]

On 10/11/2016 01:13 PM, Nandor Han wrote:
> The residue calculation was taking in consideration that dma
> transaction status will be always retrieved in the dma callback
> used to inform that dma transfer is complete. However this is not
> the case for all subsystems that use dma. Some subsystems use a
> timer to check the dma status periodically.
> 
> Therefore the calculation was updated and residue is calculated
> accordingly by a) update the residue calculation taking in
> consideration the last used buffer index by using *buf_ptail* variable
> and b) chn_real_count (number of bytes transferred) is initialized to
> zero, when dma channel is created, to avoid using an uninitialized
> value in residue calculation when dma status is checked without
> waiting dma complete event.
> 
> Signed-off-by: Nandor Han <nandor.han@ge.com>

On MX6SX with WM9712 AC97 codec:
Tested-by: Marek Vasut <marex@denx.de>

Thanks!

> ---
>  drivers/dma/imx-sdma.c | 13 +++++++++----
>  1 file changed, 9 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c
> index b9629b2..d1651a5 100644
> --- a/drivers/dma/imx-sdma.c
> +++ b/drivers/dma/imx-sdma.c
> @@ -298,6 +298,7 @@ struct sdma_engine;
>   * @event_id1		for channels that use 2 events
>   * @word_size		peripheral access size
>   * @buf_tail		ID of the buffer that was processed
> + * @buf_ptail		ID of the previous buffer that was processed
>   * @num_bd		max NUM_BD. number of descriptors currently handling
>   */
>  struct sdma_channel {
> @@ -309,6 +310,7 @@ struct sdma_channel {
>  	unsigned int			event_id1;
>  	enum dma_slave_buswidth		word_size;
>  	unsigned int			buf_tail;
> +	unsigned int			buf_ptail;
>  	unsigned int			num_bd;
>  	unsigned int			period_len;
>  	struct sdma_buffer_descriptor	*bd;
> @@ -700,6 +702,8 @@ static void sdma_update_channel_loop(struct sdma_channel *sdmac)
>  		sdmac->chn_real_count = bd->mode.count;
>  		bd->mode.status |= BD_DONE;
>  		bd->mode.count = sdmac->period_len;
> +		sdmac->buf_ptail = sdmac->buf_tail;
> +		sdmac->buf_tail = (sdmac->buf_tail + 1) % sdmac->num_bd;
>  
>  		/*
>  		 * The callback is called from the interrupt context in order
> @@ -710,9 +714,6 @@ static void sdma_update_channel_loop(struct sdma_channel *sdmac)
>  
>  		dmaengine_desc_get_callback_invoke(&sdmac->desc, NULL);
>  
> -		sdmac->buf_tail++;
> -		sdmac->buf_tail %= sdmac->num_bd;
> -
>  		if (error)
>  			sdmac->status = old_status;
>  	}
> @@ -1186,6 +1187,8 @@ static struct dma_async_tx_descriptor *sdma_prep_slave_sg(
>  	sdmac->flags = 0;
>  
>  	sdmac->buf_tail = 0;
> +	sdmac->buf_ptail = 0;
> +	sdmac->chn_real_count = 0;
>  
>  	dev_dbg(sdma->dev, "setting up %d entries for channel %d.\n",
>  			sg_len, channel);
> @@ -1288,6 +1291,8 @@ static struct dma_async_tx_descriptor *sdma_prep_dma_cyclic(
>  	sdmac->status = DMA_IN_PROGRESS;
>  
>  	sdmac->buf_tail = 0;
> +	sdmac->buf_ptail = 0;
> +	sdmac->chn_real_count = 0;
>  	sdmac->period_len = period_len;
>  
>  	sdmac->flags |= IMX_DMA_SG_LOOP;
> @@ -1385,7 +1390,7 @@ static enum dma_status sdma_tx_status(struct dma_chan *chan,
>  	u32 residue;
>  
>  	if (sdmac->flags & IMX_DMA_SG_LOOP)
> -		residue = (sdmac->num_bd - sdmac->buf_tail) *
> +		residue = (sdmac->num_bd - sdmac->buf_ptail) *
>  			   sdmac->period_len - sdmac->chn_real_count;
>  	else
>  		residue = sdmac->chn_count - sdmac->chn_real_count;
> 


-- 
Best regards,
Marek Vasut

Re: [PATCH 1/1] dmaengine: imx-sdma - correct the dma transfer residue calculation

[Vinod Koul]

On Tue, Oct 11, 2016 at 02:13:41PM +0300, Nandor Han wrote:
> The residue calculation was taking in consideration that dma
> transaction status will be always retrieved in the dma callback
> used to inform that dma transfer is complete. However this is not
> the case for all subsystems that use dma. Some subsystems use a
> timer to check the dma status periodically.
> 
> Therefore the calculation was updated and residue is calculated
> accordingly by a) update the residue calculation taking in
> consideration the last used buffer index by using *buf_ptail* variable
> and b) chn_real_count (number of bytes transferred) is initialized to
> zero, when dma channel is created, to avoid using an uninitialized
> value in residue calculation when dma status is checked without
> waiting dma complete event.

Looks to be missed earier, so applying now

Thanks
-- 
~Vinod