drivers: serial: add driver for Microchip PIC32 UART controller.

This adds PIC32 UART controller support based on driver model.

Signed-off-by: Paul Thacker <paul.thacker@microchip.com>
Signed-off-by: Purna Chandra Mandal <purna.mandal@microchip.com>
Reviewed-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

doc/device-tree-bindings/serial/microchip,pic32-uart.txt

@@ -0,0 +1,5 @@
+* Microchip PIC32 serial UART
+
+Required properties:
+- compatible: must be "microchip,pic32mzda-uart".
+- reg: exactly one register range.

drivers/serial/Kconfig

@@ -150,6 +150,14 @@ config DEBUG_UART_PL011
 	  work. The driver will be available until the real driver model
 	  serial is running.
 
+config DEBUG_UART_PIC32
+	bool "Microchip PIC32"
+	depends on PIC32_SERIAL
+	help
+	  Select this to enable a debug UART using the serial_pic32 driver. You
+	  will need to provide parameters to make this work. The driver will
+	  be available until the real driver model serial is running.
+
 endchoice
 
 config DEBUG_UART_BASE
@@ -241,6 +249,13 @@ config FSL_LPUART
 	  Select this to enable a Low Power UART for Freescale VF610 and
 	  QorIQ Layerscape devices.
 
+config PIC32_SERIAL
+	bool "Support for Microchip PIC32 on-chip UART"
+	depends on DM_SERIAL && MACH_PIC32
+	default y
+	help
+	  Support for the UART found on Microchip PIC32 SoC's.
+
 config SYS_NS16550
 	bool "NS16550 UART or compatible"
 	help

drivers/serial/Makefile

@@ -41,6 +41,7 @@ obj-$(CONFIG_MXS_AUART) += mxs_auart.o
 obj-$(CONFIG_ARC_SERIAL) += serial_arc.o
 obj-$(CONFIG_UNIPHIER_SERIAL) += serial_uniphier.o
 obj-$(CONFIG_STM32_SERIAL) += serial_stm32.o
+obj-$(CONFIG_PIC32_SERIAL) += serial_pic32.o
 
 ifndef CONFIG_SPL_BUILD
 obj-$(CONFIG_USB_TTY) += usbtty.o

drivers/serial/serial_pic32.c

@@ -0,0 +1,198 @@
+/*
+ * (c) 2015 Paul Thacker <paul.thacker@microchip.com>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ *
+ */
+#include <common.h>
+#include <clk.h>
+#include <dm.h>
+#include <serial.h>
+#include <wait_bit.h>
+#include <mach/pic32.h>
+#include <dt-bindings/clock/microchip,clock.h>
+
+DECLARE_GLOBAL_DATA_PTR;
+
+/* UART Control Registers */
+#define U_MOD		0x00
+#define U_MODCLR	(U_MOD + _CLR_OFFSET)
+#define U_MODSET	(U_MOD + _SET_OFFSET)
+#define U_STA		0x10
+#define U_STACLR	(U_STA + _CLR_OFFSET)
+#define U_STASET	(U_STA + _SET_OFFSET)
+#define U_TXR		0x20
+#define U_RXR		0x30
+#define U_BRG		0x40
+
+/* U_MOD bits */
+#define UART_ENABLE		BIT(15)
+
+/* U_STA bits */
+#define UART_RX_ENABLE		BIT(12)
+#define UART_TX_BRK		BIT(11)
+#define UART_TX_ENABLE		BIT(10)
+#define UART_TX_FULL		BIT(9)
+#define UART_TX_EMPTY		BIT(8)
+#define UART_RX_OVER		BIT(1)
+#define UART_RX_DATA_AVAIL	BIT(0)
+
+struct pic32_uart_priv {
+	void __iomem *base;
+	ulong uartclk;
+};
+
+/*
+ * Initialize the serial port with the given baudrate.
+ * The settings are always 8 data bits, no parity, 1 stop bit, no start bits.
+ */
+static int pic32_serial_init(void __iomem *base, ulong clk, u32 baudrate)
+{
+	u32 div = DIV_ROUND_CLOSEST(clk, baudrate * 16);
+
+	/* wait for TX FIFO to empty */
+	wait_for_bit(__func__, base + U_STA, UART_TX_EMPTY,
+		     true, CONFIG_SYS_HZ, false);
+
+	/* send break */
+	writel(UART_TX_BRK, base + U_STASET);
+
+	/* disable and clear mode */
+	writel(0, base + U_MOD);
+	writel(0, base + U_STA);
+
+	/* set baud rate generator */
+	writel(div - 1, base + U_BRG);
+
+	/* enable the UART for TX and RX */
+	writel(UART_TX_ENABLE | UART_RX_ENABLE, base + U_STASET);
+
+	/* enable the UART */
+	writel(UART_ENABLE, base + U_MODSET);
+	return 0;
+}
+
+/* Check whether any char pending in RX fifo */
+static int pic32_uart_pending_input(void __iomem *base)
+{
+	/* check if rx buffer overrun error has occurred */
+	if (readl(base + U_STA) & UART_RX_OVER) {
+		readl(base + U_RXR);
+
+		/* clear overrun error to keep receiving */
+		writel(UART_RX_OVER, base + U_STACLR);
+	}
+
+	/* In PIC32 there is no way to know number of outstanding
+	 * chars in rx-fifo. Only it can be known whether there is any.
+	 */
+	return readl(base + U_STA) & UART_RX_DATA_AVAIL;
+}
+
+static int pic32_uart_pending(struct udevice *dev, bool input)
+{
+	struct pic32_uart_priv *priv = dev_get_priv(dev);
+
+	if (input)
+		return pic32_uart_pending_input(priv->base);
+
+	return !(readl(priv->base + U_STA) & UART_TX_EMPTY);
+}
+
+static int pic32_uart_setbrg(struct udevice *dev, int baudrate)
+{
+	struct pic32_uart_priv *priv = dev_get_priv(dev);
+
+	return pic32_serial_init(priv->base, priv->uartclk, baudrate);
+}
+
+static int pic32_uart_putc(struct udevice *dev, const char ch)
+{
+	struct pic32_uart_priv *priv = dev_get_priv(dev);
+
+	/* Check if Tx FIFO is full */
+	if (readl(priv->base + U_STA) & UART_TX_FULL)
+		return -EAGAIN;
+
+	/* pump the char to tx buffer */
+	writel(ch, priv->base + U_TXR);
+
+	return 0;
+}
+
+static int pic32_uart_getc(struct udevice *dev)
+{
+	struct pic32_uart_priv *priv = dev_get_priv(dev);
+
+	/* return error if RX fifo is empty */
+	if (!pic32_uart_pending_input(priv->base))
+		return -EAGAIN;
+
+	/* read the character from rx buffer */
+	return readl(priv->base + U_RXR) & 0xff;
+}
+
+static int pic32_uart_probe(struct udevice *dev)
+{
+	struct pic32_uart_priv *priv = dev_get_priv(dev);
+	struct udevice *clkdev;
+	fdt_addr_t addr;
+	fdt_size_t size;
+	int ret;
+
+	/* get address */
+	addr = fdtdec_get_addr_size(gd->fdt_blob, dev->of_offset, "reg", &size);
+	if (addr == FDT_ADDR_T_NONE)
+		return -EINVAL;
+
+	priv->base = ioremap(addr, size);
+
+	/* get clock rate */
+	ret = clk_get_by_index(dev, 0, &clkdev);
+	if (ret < 0)
+		return ret;
+	priv->uartclk = clk_get_periph_rate(clkdev, ret);
+
+	/* initialize serial */
+	return pic32_serial_init(priv->base, priv->uartclk, CONFIG_BAUDRATE);
+}
+
+static const struct dm_serial_ops pic32_uart_ops = {
+	.putc		= pic32_uart_putc,
+	.pending	= pic32_uart_pending,
+	.getc		= pic32_uart_getc,
+	.setbrg		= pic32_uart_setbrg,
+};
+
+static const struct udevice_id pic32_uart_ids[] = {
+	{ .compatible = "microchip,pic32mzda-uart" },
+	{}
+};
+
+U_BOOT_DRIVER(pic32_serial) = {
+	.name		= "pic32-uart",
+	.id		= UCLASS_SERIAL,
+	.of_match	= pic32_uart_ids,
+	.probe		= pic32_uart_probe,
+	.ops		= &pic32_uart_ops,
+	.flags		= DM_FLAG_PRE_RELOC,
+	.priv_auto_alloc_size = sizeof(struct pic32_uart_priv),
+};
+
+#ifdef CONFIG_DEBUG_UART_PIC32
+#include <debug_uart.h>
+
+static inline void _debug_uart_init(void)
+{
+	void __iomem *base = (void __iomem *)CONFIG_DEBUG_UART_BASE;
+
+	pic32_serial_init(base, CONFIG_DEBUG_UART_CLOCK, CONFIG_BAUDRATE);
+}
+
+static inline void _debug_uart_putc(int ch)
+{
+	writel(ch, CONFIG_DEBUG_UART_BASE + U_TXR);
+}
+
+DEBUG_UART_FUNCS
+#endif