serial: xuartps: Adds RXBS register support for zynqmp

This patch adds RXBS register access support for zynqmp.
To avoid the corner error conditions it will consider only
RXBS[2:0] bits while checking the error conditions
(Parity,Framing and BRAK).
Signed-off-by: Nava kishore Manne <navam@xilinx.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/xilinx_uartps.c

@@ -68,6 +68,7 @@ MODULE_PARM_DESC(rx_timeout, "Rx timeout, 1-255");
 #define CDNS_UART_IRRX_PWIDTH	0x3C  /* IR Min Received Pulse Width */
 #define CDNS_UART_IRTX_PWIDTH	0x40  /* IR Transmitted pulse Width */
 #define CDNS_UART_TXWM		0x44  /* TX FIFO Trigger Level */
+#define CDNS_UART_RXBS		0x48  /* RX FIFO byte status register */
 
 /* Control Register Bit Definitions */
 #define CDNS_UART_CR_STOPBRK	0x00000100  /* Stop TX break */
@@ -79,6 +80,9 @@ MODULE_PARM_DESC(rx_timeout, "Rx timeout, 1-255");
 #define CDNS_UART_CR_TXRST	0x00000002  /* TX logic reset */
 #define CDNS_UART_CR_RXRST	0x00000001  /* RX logic reset */
 #define CDNS_UART_CR_RST_TO	0x00000040  /* Restart Timeout Counter */
+#define CDNS_UART_RXBS_PARITY    0x00000001 /* Parity error status */
+#define CDNS_UART_RXBS_FRAMING   0x00000002 /* Framing error status */
+#define CDNS_UART_RXBS_BRK       0x00000004 /* Overrun error status */
 
 /*
  * Mode Register:
@@ -131,8 +135,9 @@ MODULE_PARM_DESC(rx_timeout, "Rx timeout, 1-255");
 				 CDNS_UART_IXR_TOUT)
 
 /* Goes in read_status_mask for break detection as the HW doesn't do it*/
-#define CDNS_UART_IXR_BRK	0x80000000
+#define CDNS_UART_IXR_BRK	0x00002000
 
+#define CDNS_UART_RXBS_SUPPORT BIT(1)
 /*
  * Modem Control register:
  * The read/write Modem Control register controls the interface with the modem
@@ -172,18 +177,29 @@ struct cdns_uart {
 	struct clk		*pclk;
 	unsigned int		baud;
 	struct notifier_block	clk_rate_change_nb;
+	u32			quirks;
+};
+struct cdns_platform_data {
+	u32 quirks;
 };
 #define to_cdns_uart(_nb) container_of(_nb, struct cdns_uart, \
 		clk_rate_change_nb);
 
 static void cdns_uart_handle_rx(struct uart_port *port, unsigned int isrstatus)
 {
+	struct cdns_uart *cdns_uart = port->private_data;
+	bool is_rxbs_support;
+	unsigned int rxbs_status = 0;
+	unsigned int status_mask;
+
+	is_rxbs_support = cdns_uart->quirks & CDNS_UART_RXBS_SUPPORT;
+
 	/*
 	 * There is no hardware break detection, so we interpret framing
 	 * error with all-zeros data as a break sequence. Most of the time,
 	 * there's another non-zero byte at the end of the sequence.
 	 */
-	if (isrstatus & CDNS_UART_IXR_FRAMING) {
+	if (!is_rxbs_support && (isrstatus & CDNS_UART_IXR_FRAMING)) {
 		while (!(readl(port->membase + CDNS_UART_SR) &
 					CDNS_UART_SR_RXEMPTY)) {
 			if (!readl(port->membase + CDNS_UART_FIFO)) {
@@ -200,6 +216,8 @@ static void cdns_uart_handle_rx(struct uart_port *port, unsigned int isrstatus)
 
 	isrstatus &= port->read_status_mask;
 	isrstatus &= ~port->ignore_status_mask;
+	status_mask = port->read_status_mask;
+	status_mask &= ~port->ignore_status_mask;
 
 	if (!(isrstatus & (CDNS_UART_IXR_TOUT | CDNS_UART_IXR_RXTRIG)))
 		return;
@@ -208,6 +226,9 @@ static void cdns_uart_handle_rx(struct uart_port *port, unsigned int isrstatus)
 		u32 data;
 		char status = TTY_NORMAL;
 
+		if (is_rxbs_support)
+			rxbs_status = readl(port->membase + CDNS_UART_RXBS);
+
 		data = readl(port->membase + CDNS_UART_FIFO);
 
 		/* Non-NULL byte after BREAK is garbage (99%) */
@@ -217,21 +238,41 @@ static void cdns_uart_handle_rx(struct uart_port *port, unsigned int isrstatus)
 			if (uart_handle_break(port))
 				continue;
 		}
+		if (is_rxbs_support && (rxbs_status & CDNS_UART_RXBS_BRK)) {
+			port->icount.brk++;
+			status = TTY_BREAK;
+			if (uart_handle_break(port))
+				continue;
+		}
 
 		if (uart_handle_sysrq_char(port, data))
 			continue;
 
 		port->icount.rx++;
 
+		if (is_rxbs_support) {
+			if ((rxbs_status & CDNS_UART_RXBS_PARITY)
+				&& (status_mask & CDNS_UART_IXR_PARITY)) {
+				port->icount.parity++;
+				status = TTY_PARITY;
+			}
+			if ((rxbs_status & CDNS_UART_RXBS_FRAMING)
+				&& (status_mask & CDNS_UART_IXR_PARITY)) {
+				port->icount.frame++;
+				status = TTY_FRAME;
+			}
+		} else {
 			if (isrstatus & CDNS_UART_IXR_PARITY) {
 				port->icount.parity++;
 				status = TTY_PARITY;
-		} else if (isrstatus & CDNS_UART_IXR_FRAMING) {
+			}
+			if (isrstatus & CDNS_UART_IXR_FRAMING) {
 				port->icount.frame++;
 				status = TTY_FRAME;
-		} else if (isrstatus & CDNS_UART_IXR_OVERRUN) {
-			port->icount.overrun++;
 			}
+		}
+		if (isrstatus & CDNS_UART_IXR_OVERRUN)
+			port->icount.overrun++;
 
 		uart_insert_char(port, isrstatus, CDNS_UART_IXR_OVERRUN,
 				 data, status);
@@ -736,10 +777,14 @@ static void cdns_uart_set_termios(struct uart_port *port,
  */
 static int cdns_uart_startup(struct uart_port *port)
 {
+	struct cdns_uart *cdns_uart = port->private_data;
+	bool is_brk_support;
 	int ret;
 	unsigned long flags;
 	unsigned int status = 0;
 
+	is_brk_support = cdns_uart->quirks & CDNS_UART_RXBS_SUPPORT;
+
 	spin_lock_irqsave(&port->lock, flags);
 
 	/* Disable the TX and RX */
@@ -794,6 +839,10 @@ static int cdns_uart_startup(struct uart_port *port)
 	}
 
 	/* Set the Interrupt Registers with desired interrupts */
+	if (is_brk_support)
+		writel(CDNS_UART_RX_IRQS | CDNS_UART_IXR_BRK,
+					port->membase + CDNS_UART_IER);
+	else
 		writel(CDNS_UART_RX_IRQS, port->membase + CDNS_UART_IER);
 
 	return 0;
@@ -1328,6 +1377,18 @@ static int cdns_uart_resume(struct device *device)
 static SIMPLE_DEV_PM_OPS(cdns_uart_dev_pm_ops, cdns_uart_suspend,
 		cdns_uart_resume);
 
+static const struct cdns_platform_data zynqmp_uart_def = {
+				.quirks = CDNS_UART_RXBS_SUPPORT, };
+
+/* Match table for of_platform binding */
+static const struct of_device_id cdns_uart_of_match[] = {
+	{ .compatible = "xlnx,xuartps", },
+	{ .compatible = "cdns,uart-r1p8", },
+	{ .compatible = "cdns,uart-r1p12", .data = &zynqmp_uart_def },
+	{}
+};
+MODULE_DEVICE_TABLE(of, cdns_uart_of_match);
+
 /**
  * cdns_uart_probe - Platform driver probe
  * @pdev: Pointer to the platform device structure
@@ -1340,12 +1401,20 @@ static int cdns_uart_probe(struct platform_device *pdev)
 	struct uart_port *port;
 	struct resource *res;
 	struct cdns_uart *cdns_uart_data;
+	const struct of_device_id *match;
 
 	cdns_uart_data = devm_kzalloc(&pdev->dev, sizeof(*cdns_uart_data),
 			GFP_KERNEL);
 	if (!cdns_uart_data)
 		return -ENOMEM;
 
+	match = of_match_node(cdns_uart_of_match, pdev->dev.of_node);
+	if (match && match->data) {
+		const struct cdns_platform_data *data = match->data;
+
+		cdns_uart_data->quirks = data->quirks;
+	}
+
 	cdns_uart_data->pclk = devm_clk_get(&pdev->dev, "pclk");
 	if (IS_ERR(cdns_uart_data->pclk)) {
 		cdns_uart_data->pclk = devm_clk_get(&pdev->dev, "aper_clk");
@@ -1471,14 +1540,6 @@ static int cdns_uart_remove(struct platform_device *pdev)
 	return rc;
 }
 
-/* Match table for of_platform binding */
-static const struct of_device_id cdns_uart_of_match[] = {
-	{ .compatible = "xlnx,xuartps", },
-	{ .compatible = "cdns,uart-r1p8", },
-	{}
-};
-MODULE_DEVICE_TABLE(of, cdns_uart_of_match);
-
 static struct platform_driver cdns_uart_platform_driver = {
 	.probe   = cdns_uart_probe,
 	.remove  = cdns_uart_remove,