serial: stm32: add fifo support

This patch adds fifo mode support for rx and tx.

A fifo configuration is set in each port structure.
Add has_fifo flag to usart configuration to use fifo only when possible.
Signed-off-by: Gerald Baeza <gerald.baeza@st.com>
Signed-off-by: Bich Hemon <bich.hemon@st.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/stm32-usart.c

@@ -468,6 +468,8 @@ static int stm32_startup(struct uart_port *port)
 	}
 
 	val = USART_CR1_RXNEIE | USART_CR1_TE | USART_CR1_RE;
+	if (stm32_port->fifoen)
+		val |= USART_CR1_FIFOEN;
 	stm32_set_bits(port, ofs->cr1, val);
 
 	return 0;
@@ -482,6 +484,8 @@ static void stm32_shutdown(struct uart_port *port)
 
 	val = USART_CR1_TXEIE | USART_CR1_RXNEIE | USART_CR1_TE | USART_CR1_RE;
 	val |= BIT(cfg->uart_enable_bit);
+	if (stm32_port->fifoen)
+		val |= USART_CR1_FIFOEN;
 	stm32_clr_bits(port, ofs->cr1, val);
 
 	dev_pm_clear_wake_irq(port->dev);
@@ -512,6 +516,8 @@ static void stm32_set_termios(struct uart_port *port, struct ktermios *termios,
 
 	cr1 = USART_CR1_TE | USART_CR1_RE | USART_CR1_RXNEIE;
 	cr1 |= BIT(cfg->uart_enable_bit);
+	if (stm32_port->fifoen)
+		cr1 |= USART_CR1_FIFOEN;
 	cr2 = 0;
 	cr3 = 0;
 
@@ -676,6 +682,7 @@ static int stm32_init_port(struct stm32_port *stm32port,
 	port->dev	= &pdev->dev;
 	port->irq	= platform_get_irq(pdev, 0);
 	stm32port->wakeirq = platform_get_irq(pdev, 1);
+	stm32port->fifoen = stm32port->info->cfg.has_fifo;
 
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	port->membase = devm_ioremap_resource(&pdev->dev, res);

drivers/tty/serial/stm32-usart.h

@@ -26,6 +26,7 @@ struct stm32_usart_config {
 	u8 uart_enable_bit; /* USART_CR1_UE */
 	bool has_7bits_data;
 	bool has_wakeup;
+	bool has_fifo;
 };
 
 struct stm32_usart_info {
@@ -94,6 +95,7 @@ struct stm32_usart_info stm32h7_info = {
 		.uart_enable_bit = 0,
 		.has_7bits_data = true,
 		.has_wakeup = true,
+		.has_fifo = true,
 	}
 };
 
@@ -159,6 +161,7 @@ struct stm32_usart_info stm32h7_info = {
 #define USART_CR1_EOBIE		BIT(27)		/* F7 */
 #define USART_CR1_M1		BIT(28)		/* F7 */
 #define USART_CR1_IE_MASK	(GENMASK(8, 4) | BIT(14) | BIT(26) | BIT(27))
+#define USART_CR1_FIFOEN	BIT(29)		/* H7 */
 
 /* USART_CR2 */
 #define USART_CR2_ADD_MASK	GENMASK(3, 0)	/* F4 */
@@ -253,6 +256,7 @@ struct stm32_port {
 	int last_res;
 	bool tx_dma_busy;	 /* dma tx busy               */
 	bool hw_flow_control;
+	bool fifoen;
 	int wakeirq;
 };