[PATCH v2] serial: uartlite: Add support to work with any endianness

[Michal Simek]

From: T Karthik Reddy <t.karthik.reddy at xilinx.com>

This endinness changes are taken from linux uartlite driver.
Reset TX fifo in control register and check TX fifo empty
flag in lower byte of the status register to detect if it
is a little endian system. Based on this check, program the
registers with le32 or be32 through out the driver.

Signed-off-by: T Karthik Reddy <t.karthik.reddy at xilinx.com>
Signed-off-by: Ashok Reddy Soma <ashok.reddy.soma at xilinx.com>
Signed-off-by: Michal Simek <michal.simek at xilinx.com>
---

Changes in v2:
- Use simple mechanism to support le and be
- Update debug uartlite to support le and be
- Reset RX/TX FIFO for little endian systems

 drivers/serial/serial_xuartlite.c | 64 +++++++++++++++++++++++--------
 1 file changed, 48 insertions(+), 16 deletions(-)

diff --git a/drivers/serial/serial_xuartlite.c b/drivers/serial/serial_xuartlite.c
index 5116d13751de..236ab860ad87 100644
--- a/drivers/serial/serial_xuartlite.c
+++ b/drivers/serial/serial_xuartlite.c
@@ -23,6 +23,8 @@
 #define ULITE_CONTROL_RST_TX	0x01
 #define ULITE_CONTROL_RST_RX	0x02
 
+static bool little_endian;
+
 struct uartlite {
 	unsigned int rx_fifo;
 	unsigned int tx_fifo;
@@ -34,15 +36,31 @@ struct uartlite_platdata {
 	struct uartlite *regs;
 };
 
+static u32 uart_in32(void __iomem *addr)
+{
+	if (little_endian)
+		return in_le32(addr);
+	else
+		return in_be32(addr);
+}
+
+static void uart_out32(void __iomem *addr, u32 val)
+{
+	if (little_endian)
+		out_le32(addr, val);
+	else
+		out_be32(addr, val);
+}
+
 static int uartlite_serial_putc(struct udevice *dev, const char ch)
 {
 	struct uartlite_platdata *plat = dev_get_platdata(dev);
 	struct uartlite *regs = plat->regs;
 
-	if (in_be32(&regs->status) & SR_TX_FIFO_FULL)
+	if (uart_in32(&regs->status) & SR_TX_FIFO_FULL)
 		return -EAGAIN;
 
-	out_be32(&regs->tx_fifo, ch & 0xff);
+	uart_out32(&regs->tx_fifo, ch & 0xff);
 
 	return 0;
 }
@@ -52,10 +70,10 @@ static int uartlite_serial_getc(struct udevice *dev)
 	struct uartlite_platdata *plat = dev_get_platdata(dev);
 	struct uartlite *regs = plat->regs;
 
-	if (!(in_be32(&regs->status) & SR_RX_FIFO_VALID_DATA))
+	if (!(uart_in32(&regs->status) & SR_RX_FIFO_VALID_DATA))
 		return -EAGAIN;
 
-	return in_be32(&regs->rx_fifo) & 0xff;
+	return uart_in32(&regs->rx_fifo) & 0xff;
 }
 
 static int uartlite_serial_pending(struct udevice *dev, bool input)
@@ -64,19 +82,26 @@ static int uartlite_serial_pending(struct udevice *dev, bool input)
 	struct uartlite *regs = plat->regs;
 
 	if (input)
-		return in_be32(&regs->status) & SR_RX_FIFO_VALID_DATA;
+		return uart_in32(&regs->status) & SR_RX_FIFO_VALID_DATA;
 
-	return !(in_be32(&regs->status) & SR_TX_FIFO_EMPTY);
+	return !(uart_in32(&regs->status) & SR_TX_FIFO_EMPTY);
 }
 
 static int uartlite_serial_probe(struct udevice *dev)
 {
 	struct uartlite_platdata *plat = dev_get_platdata(dev);
 	struct uartlite *regs = plat->regs;
-
-	out_be32(&regs->control, 0);
-	out_be32(&regs->control, ULITE_CONTROL_RST_RX | ULITE_CONTROL_RST_TX);
-	in_be32(&regs->control);
+	int ret;
+
+	uart_out32(&regs->control, 0);
+	uart_out32(&regs->control, ULITE_CONTROL_RST_RX | ULITE_CONTROL_RST_TX);
+	ret = uart_in32(&regs->status);
+	/* Endianness detection */
+	if ((ret & SR_TX_FIFO_EMPTY) != SR_TX_FIFO_EMPTY) {
+		little_endian = true;
+		uart_out32(&regs->control, ULITE_CONTROL_RST_RX |
+			   ULITE_CONTROL_RST_TX);
+	}
 
 	return 0;
 }
@@ -119,20 +144,27 @@ U_BOOT_DRIVER(serial_uartlite) = {
 static inline void _debug_uart_init(void)
 {
 	struct uartlite *regs = (struct uartlite *)CONFIG_DEBUG_UART_BASE;
-
-	out_be32(&regs->control, 0);
-	out_be32(&regs->control, ULITE_CONTROL_RST_RX | ULITE_CONTROL_RST_TX);
-	in_be32(&regs->control);
+	int ret;
+
+	uart_out32(&regs->control, 0);
+	uart_out32(&regs->control, ULITE_CONTROL_RST_RX | ULITE_CONTROL_RST_TX);
+	uart_in32(&regs->status);
+	/* Endianness detection */
+	if ((ret & SR_TX_FIFO_EMPTY) != SR_TX_FIFO_EMPTY) {
+		little_endian = true;
+		uart_out32(&regs->control, ULITE_CONTROL_RST_RX |
+			   ULITE_CONTROL_RST_TX);
+	}
 }
 
 static inline void _debug_uart_putc(int ch)
 {
 	struct uartlite *regs = (struct uartlite *)CONFIG_DEBUG_UART_BASE;
 
-	while (in_be32(&regs->status) & SR_TX_FIFO_FULL)
+	while (uart_in32(&regs->status) & SR_TX_FIFO_FULL)
 		;
 
-	out_be32(&regs->tx_fifo, ch & 0xff);
+	uart_out32(&regs->tx_fifo, ch & 0xff);
 }
 
 DEBUG_UART_FUNCS
-- 
2.28.0