The dma_sync_sg_for_device() functions should be called with the same
nents as the dma_map_sg(), not the value the map function returned.

Fixes: da3564ee027e ("pch_uart: add multi-scatter processing")
Signed-off-by: Thomas Fourier <fourier.thomas@gmail.com>
---
 drivers/tty/serial/pch_uart.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/tty/serial/pch_uart.c b/drivers/tty/serial/pch_uart.c
index 508e8c6f01d4..884fefbfd5a1 100644
--- a/drivers/tty/serial/pch_uart.c
+++ b/drivers/tty/serial/pch_uart.c
@@ -954,7 +954,7 @@ static unsigned int dma_handle_tx(struct eg20t_port *priv)
 			__func__);
 		return 0;
 	}
-	dma_sync_sg_for_device(port->dev, priv->sg_tx_p, nent, DMA_TO_DEVICE);
+	dma_sync_sg_for_device(port->dev, priv->sg_tx_p, num, DMA_TO_DEVICE);
 	priv->desc_tx = desc;
 	desc->callback = pch_dma_tx_complete;
 	desc->callback_param = priv;
-- 
2.43.0

On 30. 06. 25, 14:10, Thomas Fourier wrote:
> The dma_sync_sg_for_device() functions should be called with the same
> nents as the dma_map_sg(), not the value the map function returned.

Care to explain why do you intend to sync more than mapped? "should be 
called" is way to vague.

> Fixes: da3564ee027e ("pch_uart: add multi-scatter processing")
> Signed-off-by: Thomas Fourier <fourier.thomas@gmail.com>
> ---
>   drivers/tty/serial/pch_uart.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/tty/serial/pch_uart.c b/drivers/tty/serial/pch_uart.c
> index 508e8c6f01d4..884fefbfd5a1 100644
> --- a/drivers/tty/serial/pch_uart.c
> +++ b/drivers/tty/serial/pch_uart.c
> @@ -954,7 +954,7 @@ static unsigned int dma_handle_tx(struct eg20t_port *priv)
>   			__func__);
>   		return 0;
>   	}
> -	dma_sync_sg_for_device(port->dev, priv->sg_tx_p, nent, DMA_TO_DEVICE);
> +	dma_sync_sg_for_device(port->dev, priv->sg_tx_p, num, DMA_TO_DEVICE);
>   	priv->desc_tx = desc;
>   	desc->callback = pch_dma_tx_complete;
>   	desc->callback_param = priv;


-- 
js
suse labs

On Mon, Jun 30, 2025 at 03:01:01PM +0200, Jiri Slaby wrote:
> On 30. 06. 25, 14:10, Thomas Fourier wrote:
> > The dma_sync_sg_for_device() functions should be called with the same
> > nents as the dma_map_sg(), not the value the map function returned.
> 
> Care to explain why do you intend to sync more than mapped? "should be
> called" is way to vague.

It's documented as the correct use of the DMA streaming API.
Should we go deeper and understand why?

-- 
With Best Regards,
Andy Shevchenko

On 30. 06. 25, 15:13, Andy Shevchenko wrote:
> On Mon, Jun 30, 2025 at 03:01:01PM +0200, Jiri Slaby wrote:
>> On 30. 06. 25, 14:10, Thomas Fourier wrote:
>>> The dma_sync_sg_for_device() functions should be called with the same
>>> nents as the dma_map_sg(), not the value the map function returned.
>>
>> Care to explain why do you intend to sync more than mapped? "should be
>> called" is way to vague.
> 
> It's documented as the correct use of the DMA streaming API.
> Should we go deeper and understand why?

That's IMO enough if he put/referenced this in the commit log...

-- 
js
suse labs

On Mon, Jun 30, 2025 at 02:10:19PM +0200, Thomas Fourier wrote:
> The dma_sync_sg_for_device() functions should be called with the same
> nents as the dma_map_sg(), not the value the map function returned.
> 
> Fixes: da3564ee027e ("pch_uart: add multi-scatter processing")
> Signed-off-by: Thomas Fourier <fourier.thomas@gmail.com>
> ---
>  drivers/tty/serial/pch_uart.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/tty/serial/pch_uart.c b/drivers/tty/serial/pch_uart.c
> index 508e8c6f01d4..884fefbfd5a1 100644
> --- a/drivers/tty/serial/pch_uart.c
> +++ b/drivers/tty/serial/pch_uart.c
> @@ -954,7 +954,7 @@ static unsigned int dma_handle_tx(struct eg20t_port *priv)
>  			__func__);
>  		return 0;
>  	}
> -	dma_sync_sg_for_device(port->dev, priv->sg_tx_p, nent, DMA_TO_DEVICE);
> +	dma_sync_sg_for_device(port->dev, priv->sg_tx_p, num, DMA_TO_DEVICE);
>  	priv->desc_tx = desc;
>  	desc->callback = pch_dma_tx_complete;
>  	desc->callback_param = priv;
> -- 
> 2.43.0
> 
> 

Hi,

This is the friendly patch-bot of Greg Kroah-Hartman.  You have sent him
a patch that has triggered this response.  He used to manually respond
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