2 files changed, 165 insertions, 53 deletions

diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index 848e063db2ae..cfdda35499e6 100644
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -165,66 +165,60 @@ static int stm32_usart_init_rs485(struct uart_port *port,
 	return uart_get_rs485_mode(port);
 }
 
-static int stm32_usart_pending_rx(struct uart_port *port, u32 *sr,
-				  int *last_res, bool threaded)
+static bool stm32_usart_rx_dma_enabled(struct uart_port *port)
 {
 	struct stm32_port *stm32_port = to_stm32_port(port);
 	const struct stm32_usart_offsets *ofs = &stm32_port->info->ofs;
-	enum dma_status status;
-	struct dma_tx_state state;
 
-	*sr = readl_relaxed(port->membase + ofs->isr);
+	if (!stm32_port->rx_ch)
+		return false;
 
-	if (threaded && stm32_port->rx_ch) {
-		status = dmaengine_tx_status(stm32_port->rx_ch,
-					     stm32_port->rx_ch->cookie,
-					     &state);
-		if (status == DMA_IN_PROGRESS && (*last_res != state.residue))
-			return 1;
-		else
-			return 0;
-	} else if (*sr & USART_SR_RXNE) {
-		return 1;
+	return !!(readl_relaxed(port->membase + ofs->cr3) & USART_CR3_DMAR);
+}
+
+/* Return true when data is pending (in pio mode), and false when no data is pending. */
+static bool stm32_usart_pending_rx_pio(struct uart_port *port, u32 *sr)
+{
+	struct stm32_port *stm32_port = to_stm32_port(port);
+	const struct stm32_usart_offsets *ofs = &stm32_port->info->ofs;
+
+	*sr = readl_relaxed(port->membase + ofs->isr);
+	/* Get pending characters in RDR or FIFO */
+	if (*sr & USART_SR_RXNE) {
+		/* Get all pending characters from the RDR or the FIFO when using interrupts */
+		if (!stm32_usart_rx_dma_enabled(port))
+			return true;
+
+		/* Handle only RX data errors when using DMA */
+		if (*sr & USART_SR_ERR_MASK)
+			return true;
 	}
-	return 0;
+
+	return false;
 }
 
-static unsigned long stm32_usart_get_char(struct uart_port *port, u32 *sr,
-					  int *last_res)
+static unsigned long stm32_usart_get_char_pio(struct uart_port *port)
 {
 	struct stm32_port *stm32_port = to_stm32_port(port);
 	const struct stm32_usart_offsets *ofs = &stm32_port->info->ofs;
 	unsigned long c;
 
-	if (stm32_port->rx_ch) {
-		c = stm32_port->rx_buf[RX_BUF_L - (*last_res)--];
-		if ((*last_res) == 0)
-			*last_res = RX_BUF_L;
-	} else {
-		c = readl_relaxed(port->membase + ofs->rdr);
-		/* apply RDR data mask */
-		c &= stm32_port->rdr_mask;
-	}
+	c = readl_relaxed(port->membase + ofs->rdr);
+	/* Apply RDR data mask */
+	c &= stm32_port->rdr_mask;
 
 	return c;
 }
 
-static void stm32_usart_receive_chars(struct uart_port *port, bool irqflag)
+static void stm32_usart_receive_chars_pio(struct uart_port *port)
 {
-	struct tty_port *tport = &port->state->port;
 	struct stm32_port *stm32_port = to_stm32_port(port);
 	const struct stm32_usart_offsets *ofs = &stm32_port->info->ofs;
-	unsigned long c, flags;
+	unsigned long c;
 	u32 sr;
 	char flag;
 
-	if (irqflag)
-		spin_lock_irqsave(&port->lock, flags);
-	else
-		spin_lock(&port->lock);
-
-	while (stm32_usart_pending_rx(port, &sr, &stm32_port->last_res,
-				      irqflag)) {
+	while (stm32_usart_pending_rx_pio(port, &sr)) {
 		sr |= USART_SR_DUMMY_RX;
 		flag = TTY_NORMAL;
 
@@ -243,7 +237,7 @@ static void stm32_usart_receive_chars(struct uart_port *port, bool irqflag)
 			writel_relaxed(sr & USART_SR_ERR_MASK,
 				       port->membase + ofs->icr);
 
-		c = stm32_usart_get_char(port, &sr, &stm32_port->last_res);
+		c = stm32_usart_get_char_pio(port);
 		port->icount.rx++;
 		if (sr & USART_SR_ERR_MASK) {
 			if (sr & USART_SR_ORE) {
@@ -277,6 +271,94 @@ static void stm32_usart_receive_chars(struct uart_port *port, bool irqflag)
 			continue;
 		uart_insert_char(port, sr, USART_SR_ORE, c, flag);
 	}
+}
+
+static void stm32_usart_push_buffer_dma(struct uart_port *port, unsigned int dma_size)
+{
+	struct stm32_port *stm32_port = to_stm32_port(port);
+	struct tty_port *ttyport = &stm32_port->port.state->port;
+	unsigned char *dma_start;
+	int dma_count, i;
+
+	dma_start = stm32_port->rx_buf + (RX_BUF_L - stm32_port->last_res);
+
+	/*
+	 * Apply rdr_mask on buffer in order to mask parity bit.
+	 * This loop is useless in cs8 mode because DMA copies only
+	 * 8 bits and already ignores parity bit.
+	 */
+	if (!(stm32_port->rdr_mask == (BIT(8) - 1)))
+		for (i = 0; i < dma_size; i++)
+			*(dma_start + i) &= stm32_port->rdr_mask;
+
+	dma_count = tty_insert_flip_string(ttyport, dma_start, dma_size);
+	port->icount.rx += dma_count;
+	if (dma_count != dma_size)
+		port->icount.buf_overrun++;
+	stm32_port->last_res -= dma_count;
+	if (stm32_port->last_res == 0)
+		stm32_port->last_res = RX_BUF_L;
+}
+
+static void stm32_usart_receive_chars_dma(struct uart_port *port)
+{
+	struct stm32_port *stm32_port = to_stm32_port(port);
+	unsigned int dma_size;
+
+	/* DMA buffer is configured in cyclic mode and handles the rollback of the buffer. */
+	if (stm32_port->rx_dma_state.residue > stm32_port->last_res) {
+		/* Conditional first part: from last_res to end of DMA buffer */
+		dma_size = stm32_port->last_res;
+		stm32_usart_push_buffer_dma(port, dma_size);
+	}
+
+	dma_size = stm32_port->last_res - stm32_port->rx_dma_state.residue;
+	stm32_usart_push_buffer_dma(port, dma_size);
+}
+
+static void stm32_usart_receive_chars(struct uart_port *port, bool irqflag)
+{
+	struct tty_port *tport = &port->state->port;
+	struct stm32_port *stm32_port = to_stm32_port(port);
+	const struct stm32_usart_offsets *ofs = &stm32_port->info->ofs;
+	enum dma_status rx_dma_status;
+	unsigned long flags;
+	u32 sr;
+
+	if (irqflag)
+		spin_lock_irqsave(&port->lock, flags);
+	else
+		spin_lock(&port->lock);
+
+	if (stm32_usart_rx_dma_enabled(port)) {
+		rx_dma_status = dmaengine_tx_status(stm32_port->rx_ch,
+						    stm32_port->rx_ch->cookie,
+						    &stm32_port->rx_dma_state);
+		if (rx_dma_status == DMA_IN_PROGRESS) {
+			/* Empty DMA buffer */
+			stm32_usart_receive_chars_dma(port);
+			sr = readl_relaxed(port->membase + ofs->isr);
+			if (sr & USART_SR_ERR_MASK) {
+				/* Disable DMA request line */
+				stm32_usart_clr_bits(port, ofs->cr3, USART_CR3_DMAR);
+
+				/* Switch to PIO mode to handle the errors */
+				stm32_usart_receive_chars_pio(port);
+
+				/* Switch back to DMA mode */
+				stm32_usart_set_bits(port, ofs->cr3, USART_CR3_DMAR);
+			}
+		} else {
+			/* Disable RX DMA */
+			dmaengine_terminate_async(stm32_port->rx_ch);
+			stm32_usart_clr_bits(port, ofs->cr3, USART_CR3_DMAR);
+			/* Fall back to interrupt mode */
+			dev_dbg(port->dev, "DMA error, fallback to irq mode\n");
+			stm32_usart_receive_chars_pio(port);
+		}
+	} else {
+		stm32_usart_receive_chars_pio(port);
+	}
 
 	if (irqflag)
 		uart_unlock_and_check_sysrq_irqrestore(port, irqflag);
@@ -318,6 +400,13 @@ static void stm32_usart_tx_interrupt_enable(struct uart_port *port)
 		stm32_usart_set_bits(port, ofs->cr1, USART_CR1_TXEIE);
 }
 
+static void stm32_usart_rx_dma_complete(void *arg)
+{
+	struct uart_port *port = arg;
+
+	stm32_usart_receive_chars(port, true);
+}
+
 static void stm32_usart_tx_interrupt_disable(struct uart_port *port)
 {
 	struct stm32_port *stm32_port = to_stm32_port(port);
@@ -484,7 +573,12 @@ static irqreturn_t stm32_usart_interrupt(int irq, void *ptr)
 			pm_wakeup_event(tport->tty->dev, 0);
 	}
 
-	if ((sr & USART_SR_RXNE) && !(stm32_port->rx_ch))
+	/*
+	 * rx errors in dma mode has to be handled ASAP to avoid overrun as the DMA request
+	 * line has been masked by HW and rx data are stacking in FIFO.
+	 */
+	if (((sr & USART_SR_RXNE) && !stm32_usart_rx_dma_enabled(port)) ||
+	    ((sr & USART_SR_ERR_MASK) && stm32_usart_rx_dma_enabled(port)))
 		stm32_usart_receive_chars(port, false);
 
 	if ((sr & USART_SR_TXE) && !(stm32_port->tx_ch)) {
@@ -493,7 +587,7 @@ static irqreturn_t stm32_usart_interrupt(int irq, void *ptr)
 		spin_unlock(&port->lock);
 	}
 
-	if (stm32_port->rx_ch)
+	if (stm32_usart_rx_dma_enabled(port))
 		return IRQ_WAKE_THREAD;
 	else
 		return IRQ_HANDLED;
@@ -815,9 +909,11 @@ static void stm32_usart_set_termios(struct uart_port *port,
 		stm32_port->cr1_irq = USART_CR1_RTOIE;
 		writel_relaxed(bits, port->membase + ofs->rtor);
 		cr2 |= USART_CR2_RTOEN;
-		/* Not using dma, enable fifo threshold irq */
-		if (!stm32_port->rx_ch)
-			stm32_port->cr3_irq =  USART_CR3_RXFTIE;
+		/*
+		 * Enable fifo threshold irq in two cases, either when there is no DMA, or when
+		 * wake up over usart, from low power until the DMA gets re-enabled by resume.
+		 */
+		stm32_port->cr3_irq =  USART_CR3_RXFTIE;
 	}
 
 	cr1 |= stm32_port->cr1_irq;
@@ -880,8 +976,16 @@ static void stm32_usart_set_termios(struct uart_port *port,
 	if ((termios->c_cflag & CREAD) == 0)
 		port->ignore_status_mask |= USART_SR_DUMMY_RX;
 
-	if (stm32_port->rx_ch)
+	if (stm32_port->rx_ch) {
+		/*
+		 * Setup DMA to collect only valid data and enable error irqs.
+		 * This also enables break reception when using DMA.
+		 */
+		cr1 |= USART_CR1_PEIE;
+		cr3 |= USART_CR3_EIE;
 		cr3 |= USART_CR3_DMAR;
+		cr3 |= USART_CR3_DDRE;
+	}
 
 	if (rs485conf->flags & SER_RS485_ENABLED) {
 		stm32_usart_config_reg_rs485(&cr1, &cr3,
@@ -1210,9 +1314,9 @@ static int stm32_usart_of_dma_rx_probe(struct stm32_port *stm32port,
 		return -ENODEV;
 	}
 
-	/* No callback as dma buffer is drained on usart interrupt */
-	desc->callback = NULL;
-	desc->callback_param = NULL;
+	/* Set DMA callback */
+	desc->callback = stm32_usart_rx_dma_complete;
+	desc->callback_param = port;
 
 	/* Push current DMA transaction in the pending queue */
 	ret = dma_submit_error(dmaengine_submit(desc));
@@ -1377,6 +1481,7 @@ static int stm32_usart_serial_remove(struct platform_device *pdev)
 	struct stm32_port *stm32_port = to_stm32_port(port);
 	const struct stm32_usart_offsets *ofs = &stm32_port->info->ofs;
 	int err;
+	u32 cr3;
 
 	pm_runtime_get_sync(&pdev->dev);
 	err = uart_remove_one_port(&stm32_usart_driver, port);
@@ -1387,7 +1492,12 @@ static int stm32_usart_serial_remove(struct platform_device *pdev)
 	pm_runtime_set_suspended(&pdev->dev);
 	pm_runtime_put_noidle(&pdev->dev);
 
-	stm32_usart_clr_bits(port, ofs->cr3, USART_CR3_DMAR);
+	stm32_usart_clr_bits(port, ofs->cr1, USART_CR1_PEIE);
+	cr3 = readl_relaxed(port->membase + ofs->cr3);
+	cr3 &= ~USART_CR3_EIE;
+	cr3 &= ~USART_CR3_DMAR;
+	cr3 &= ~USART_CR3_DDRE;
+	writel_relaxed(cr3, port->membase + ofs->cr3);
 
 	if (stm32_port->tx_ch) {
 		dmaengine_terminate_async(stm32_port->tx_ch);
diff --git a/drivers/tty/serial/stm32-usart.h b/drivers/tty/serial/stm32-usart.h
index 07ac291328cd..53bcd032fce7 100644
--- a/drivers/tty/serial/stm32-usart.h
+++ b/drivers/tty/serial/stm32-usart.h
@@ -109,7 +109,7 @@ struct stm32_usart_info stm32h7_info = {
 /* USART_SR (F4) / USART_ISR (F7) */
 #define USART_SR_PE		BIT(0)
 #define USART_SR_FE		BIT(1)
-#define USART_SR_NF		BIT(2)
+#define USART_SR_NE		BIT(2)		/* F7 (NF for F4) */
 #define USART_SR_ORE		BIT(3)
 #define USART_SR_IDLE		BIT(4)
 #define USART_SR_RXNE		BIT(5)
@@ -126,7 +126,8 @@ struct stm32_usart_info stm32h7_info = {
 #define USART_SR_SBKF		BIT(18)		/* F7 */
 #define USART_SR_WUF		BIT(20)		/* H7 */
 #define USART_SR_TEACK		BIT(21)		/* F7 */
-#define USART_SR_ERR_MASK	(USART_SR_ORE | USART_SR_FE | USART_SR_PE)
+#define USART_SR_ERR_MASK	(USART_SR_ORE | USART_SR_NE | USART_SR_FE |\
+				 USART_SR_PE)
 /* Dummy bits */
 #define USART_SR_DUMMY_RX	BIT(16)
 
@@ -246,9 +247,9 @@ struct stm32_usart_info stm32h7_info = {
 #define STM32_SERIAL_NAME "ttySTM"
 #define STM32_MAX_PORTS 8
 
-#define RX_BUF_L 200		 /* dma rx buffer length     */
-#define RX_BUF_P RX_BUF_L	 /* dma rx buffer period     */
-#define TX_BUF_L 200		 /* dma tx buffer length     */
+#define RX_BUF_L 4096		 /* dma rx buffer length     */
+#define RX_BUF_P (RX_BUF_L / 2)	 /* dma rx buffer period     */
+#define TX_BUF_L RX_BUF_L	 /* dma tx buffer length     */
 
 struct stm32_port {
 	struct uart_port port;
@@ -272,6 +273,7 @@ struct stm32_port {
 	bool wakeup_src;
 	int rdr_mask;		/* receive data register mask */
 	struct mctrl_gpios *gpios; /* modem control gpios */
+	struct dma_tx_state rx_dma_state;
 };
 
 static struct stm32_port stm32_ports[STM32_MAX_PORTS];