Merge v7.0.12linux-rolling-stable

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 14 insertions, 2 deletions

diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c
index e6b0a55f0cfb..774c0b7f8508 100644
--- a/drivers/tty/serial/qcom_geni_serial.c
+++ b/drivers/tty/serial/qcom_geni_serial.c
@@ -50,7 +50,7 @@
 #define TX_STOP_BIT_LEN_2		2
 
 /* SE_UART_RX_TRANS_CFG */
-#define UART_RX_PAR_EN			BIT(3)
+#define UART_RX_PAR_EN			BIT(4)
 
 /* SE_UART_RX_WORD_LEN */
 #define RX_WORD_LEN_MASK		GENMASK(9, 0)
@@ -1030,8 +1030,20 @@ static void qcom_geni_serial_handle_tx_dma(struct uart_port *uport)
 {
 	struct qcom_geni_serial_port *port = to_dev_port(uport);
 	struct tty_port *tport = &uport->state->port;
+	unsigned int fifo_len = kfifo_len(&tport->xmit_fifo);
+
+	/*
+	 * Only advance the kfifo if it still contains the bytes that were
+	 * transferred. uart_flush_buffer() may have run before this IRQ
+	 * fired: it calls kfifo_reset() under the port lock, making
+	 * fifo_len = 0 while tx_remaining remains non-zero. Calling
+	 * uart_xmit_advance() in that case would underflow kfifo->out past
+	 * kfifo->in, making kfifo_len() wrap to UART_XMIT_SIZE - tx_remaining
+	 * and triggering a spurious large DMA transfer of stale data.
+	 */
+	if (fifo_len >= port->tx_remaining)
+		uart_xmit_advance(uport, port->tx_remaining);
 
-	uart_xmit_advance(uport, port->tx_remaining);
 	geni_se_tx_dma_unprep(&port->se, port->tx_dma_addr, port->tx_remaining);
 	port->tx_dma_addr = 0;
 	port->tx_remaining = 0;