tty: serial: qcom_geni_serial: Remove unnecessary memory barrier

While initiating TX, only the register reads need to be ordered. The
register write order either is achieved due to data dependency or is
not required.

Use readl to achieve the read order and remove the unnecessary barrier.

Signed-off-by: Karthikeyan Ramasubramanian <kramasub@codeaurora.org>
Reviewed-by: Evan Green <evgreen@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/qcom_geni_serial.c

@@ -417,20 +417,18 @@ static void qcom_geni_serial_start_tx(struct uart_port *uport)
 	u32 status;
 
 	if (port->xfer_mode == GENI_SE_FIFO) {
-		status = readl_relaxed(uport->membase + SE_GENI_STATUS);
+		/*
+		 * readl ensures reading & writing of IRQ_EN register
+		 * is not re-ordered before checking the status of the
+		 * Serial Engine.
+		 */
+		status = readl(uport->membase + SE_GENI_STATUS);
 		if (status & M_GENI_CMD_ACTIVE)
 			return;
 
 		if (!qcom_geni_serial_tx_empty(uport))
 			return;
 
-		/*
-		 * Ensure writing to IRQ_EN & watermark registers are not
-		 * re-ordered before checking the status of the Serial
-		 * Engine and TX FIFO
-		 */
-		mb();
-
 		irq_en = readl_relaxed(uport->membase +	SE_GENI_M_IRQ_EN);
 		irq_en |= M_TX_FIFO_WATERMARK_EN | M_CMD_DONE_EN;
 
@@ -894,7 +892,7 @@ out_restart_rx:
 
 static unsigned int qcom_geni_serial_tx_empty(struct uart_port *uport)
 {
-	return !readl_relaxed(uport->membase + SE_GENI_TX_FIFO_STATUS);
+	return !readl(uport->membase + SE_GENI_TX_FIFO_STATUS);
 }
 
 #ifdef CONFIG_SERIAL_QCOM_GENI_CONSOLE