diff mbox series

serial: tegra: read DMA status before terminating

Message ID 1666074311-12764-1-git-send-email-kkartik@nvidia.com
State New
Headers
Series serial: tegra: read DMA status before terminating |

Commit Message

Kartik Rajput Oct. 18, 2022, 6:25 a.m. UTC 
  To get the valid data, read DMA status before terminating the DMA. As
dmaengine_terminate_all() deletes the DMA desc.

Fixes: e9ea096dd225 ("serial: tegra: add serial driver")

Signed-off-by: Akhil R <akhilrajeev@nvidia.com>
Signed-off-by: Kartik <kkartik@nvidia.com>
---
 drivers/tty/serial/serial-tegra.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Comments

Jon Hunter Oct. 18, 2022, 1:18 p.m. UTC | #1 
On 18/10/2022 07:25, Kartik wrote:
> To get the valid data, read DMA status before terminating the DMA. As
> dmaengine_terminate_all() deletes the DMA desc.
> 
> Fixes: e9ea096dd225 ("serial: tegra: add serial driver")
> 
> Signed-off-by: Akhil R <akhilrajeev@nvidia.com>
> Signed-off-by: Kartik <kkartik@nvidia.com>
> ---
>   drivers/tty/serial/serial-tegra.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/tty/serial/serial-tegra.c b/drivers/tty/serial/serial-tegra.c
> index b7170cb9a544..2779b4491f02 100644
> --- a/drivers/tty/serial/serial-tegra.c
> +++ b/drivers/tty/serial/serial-tegra.c
> @@ -619,8 +619,8 @@ static void tegra_uart_stop_tx(struct uart_port *u)
>   	if (tup->tx_in_progress != TEGRA_UART_TX_DMA)
>   		return;
>   
> -	dmaengine_terminate_all(tup->tx_dma_chan);
>   	dmaengine_tx_status(tup->tx_dma_chan, tup->tx_cookie, &state);
> +	dmaengine_terminate_all(tup->tx_dma_chan);

The change looks fine to me, but on further review of other similar 
drivers I see that they pause first ...

  dmaengine_pause(tup->tx_dma_chan);
  dmaengine_tx_status(tup->tx_dma_chan, tup->tx_cookie, &state);
  dmaengine_terminate_all(tup->tx_dma_chan);

This makes sense so that when we calculate the amount of the data 
transferred we get the exact amount. Can we add a pause while we are at it?

Thanks!
Jon
Kartik Rajput Oct. 18, 2022, 1:33 p.m. UTC | #2 
> The change looks fine to me, but on further review of other similar 
> drivers I see that they pause first ...
> 
>   dmaengine_pause(tup->tx_dma_chan);
>   dmaengine_tx_status(tup->tx_dma_chan, tup->tx_cookie, &state);
>   dmaengine_terminate_all(tup->tx_dma_chan);
> 
> This makes sense so that when we calculate the amount of the data 
> transferred we get the exact amount. Can we add a pause while we are at it?
> 
> Thanks!
> Jon

I agree.. I will include this in v2.

Regards,
Kartik
diff mbox series

Patch

diff --git a/drivers/tty/serial/serial-tegra.c b/drivers/tty/serial/serial-tegra.c
index b7170cb9a544..2779b4491f02 100644
--- a/drivers/tty/serial/serial-tegra.c
+++ b/drivers/tty/serial/serial-tegra.c
@@ -619,8 +619,8 @@  static void tegra_uart_stop_tx(struct uart_port *u)
 	if (tup->tx_in_progress != TEGRA_UART_TX_DMA)
 		return;
 
-	dmaengine_terminate_all(tup->tx_dma_chan);
 	dmaengine_tx_status(tup->tx_dma_chan, tup->tx_cookie, &state);
+	dmaengine_terminate_all(tup->tx_dma_chan);
 	count = tup->tx_bytes_requested - state.residue;
 	async_tx_ack(tup->tx_dma_desc);
 	uart_xmit_advance(&tup->uport, count);
@@ -763,8 +763,8 @@  static void tegra_uart_terminate_rx_dma(struct tegra_uart_port *tup)
 		return;
 	}
 
-	dmaengine_terminate_all(tup->rx_dma_chan);
 	dmaengine_tx_status(tup->rx_dma_chan, tup->rx_cookie, &state);
+	dmaengine_terminate_all(tup->rx_dma_chan);
 
 	tegra_uart_rx_buffer_push(tup, state.residue);
 	tup->rx_dma_active = false;