linux-kernel - [PATCH v2] serial: tegra: Read DMA status before terminating

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Date:   Tue, 18 Oct 2022 20:28:06 +0530
From:   Kartik <kkartik@...dia.com>
To:     <ldewangan@...dia.com>, <gregkh@...uxfoundation.org>,
        <jirislaby@...nel.org>, <thierry.reding@...il.com>,
        <jonathanh@...dia.com>, <alan@...ux.intel.com>,
        <swarren@...dia.com>, <akhilrajeev@...dia.com>,
        <linux-serial@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: [PATCH v2] serial: tegra: Read DMA status before terminating

Read the DMA status before terminating the DMA, as doing so deletes
the DMA desc.

Also, to get the correct transfer status information, pause the DMA
using dmaengine_pause() before reading the DMA status.

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

Signed-off-by: Akhil R <akhilrajeev@...dia.com>
Signed-off-by: Kartik <kkartik@...dia.com>
---
v1->v2:
 * Pause the DMA before reading the DMA status.
 * Updated commit message.

 drivers/tty/serial/serial-tegra.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/serial-tegra.c b/drivers/tty/serial/serial-tegra.c
index b7170cb9a544..cda9cd4fa92c 100644
--- a/drivers/tty/serial/serial-tegra.c
+++ b/drivers/tty/serial/serial-tegra.c
@@ -619,8 +619,9 @@ 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_pause(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 +764,9 @@ static void tegra_uart_terminate_rx_dma(struct tegra_uart_port *tup)
 		return;
 	}
 
-	dmaengine_terminate_all(tup->rx_dma_chan);
+	dmaengine_pause(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;
-- 
2.17.1