serial: tegra: update tx_circular buffer only when TX_DMA is in progress

When channel is require to stop transmit then update the Tx circular
buffer only when DMA based transfer is in progress. If there is no
DMA based transfer then no need to update the Tx buffer.
Signed-off-by: NPradeep Goudagunta <pgoudagunta@nvidia.com>
Signed-off-by: NLaxman Dewangan <ldewangan@nvidia.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/serial-tegra.c

@@ -482,6 +482,9 @@ static void tegra_uart_stop_tx(struct uart_port *u)
 	struct dma_tx_state state;
 	int count;
 
+	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);
 	count = tup->tx_bytes_requested - state.residue;