serial: Add Actions Semi OWL UART support

This commit adds Actions Semi OWL family UART support. This driver
relies on baudrate configured by primary bootloaders.

Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Reviewed-by: Simon Glass <sjg@chromium.org>

drivers/serial/Kconfig

@@ -625,6 +625,14 @@ config MSM_SERIAL
 	  for example APQ8016 and MSM8916.
 	  Single baudrate is supported in current implementation (115200).
 
+config OWL_SERIAL
+	bool "Actions Semi OWL UART"
+	depends on DM_SERIAL && ARCH_OWL
+	help
+	  If you have a Actions Semi OWL based board and want to use the on-chip
+	  serial port, say Y to this option. If unsure, say N.
+	  Single baudrate is supported in current implementation (115200).
+
 config PXA_SERIAL
 	bool "PXA serial port support"
 	help

drivers/serial/Makefile

@@ -64,6 +64,7 @@ obj-$(CONFIG_MSM_SERIAL) += serial_msm.o
 obj-$(CONFIG_MVEBU_A3700_UART) += serial_mvebu_a3700.o
 obj-$(CONFIG_MPC8XX_CONS) += serial_mpc8xx.o
 obj-$(CONFIG_NULLDEV_SERIAL) += serial_nulldev.o
+obj-$(CONFIG_OWL_SERIAL) += serial_owl.o
 
 ifndef CONFIG_SPL_BUILD
 obj-$(CONFIG_USB_TTY) += usbtty.o

drivers/serial/serial_owl.c

@@ -0,0 +1,136 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Actions Semi OWL SoCs UART driver
+ *
+ * Copyright (C) 2015 Actions Semi Co., Ltd.
+ * Copyright (C) 2018 Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
+ */
+
+#include <common.h>
+#include <clk.h>
+#include <dm.h>
+#include <errno.h>
+#include <fdtdec.h>
+#include <serial.h>
+#include <asm/io.h>
+#include <asm/types.h>
+
+/* UART Registers */
+#define	OWL_UART_CTL			(0x0000)
+#define	OWL_UART_RXDAT			(0x0004)
+#define	OWL_UART_TXDAT			(0x0008)
+#define	OWL_UART_STAT			(0x000C)
+
+/* UART_CTL Register Definitions */
+#define	OWL_UART_CTL_PRS_NONE		GENMASK(6, 4)
+#define	OWL_UART_CTL_STPS		BIT(2)
+#define	OWL_UART_CTL_DWLS		3
+
+/* UART_STAT Register Definitions */
+#define	OWL_UART_STAT_TFES		BIT(10)	/* TX FIFO Empty Status	*/
+#define	OWL_UART_STAT_RFFS		BIT(9)	/* RX FIFO full	Status */
+#define	OWL_UART_STAT_TFFU		BIT(6)	/* TX FIFO full	Status */
+#define	OWL_UART_STAT_RFEM		BIT(5)	/* RX FIFO Empty Status	*/
+
+struct owl_serial_priv {
+	phys_addr_t base;
+};
+
+int owl_serial_setbrg(struct udevice *dev, int baudrate)
+{
+	/* Driver supports only fixed baudrate */
+	return 0;
+}
+
+static int owl_serial_getc(struct udevice *dev)
+{
+	struct owl_serial_priv *priv = dev_get_priv(dev);
+
+	if (readl(priv->base + OWL_UART_STAT) & OWL_UART_STAT_RFEM)
+		return -EAGAIN;
+
+	return (int)(readl(priv->base +	OWL_UART_RXDAT));
+}
+
+static int owl_serial_putc(struct udevice *dev,	const char ch)
+{
+	struct owl_serial_priv *priv = dev_get_priv(dev);
+
+	if (readl(priv->base + OWL_UART_STAT) & OWL_UART_STAT_TFFU)
+		return -EAGAIN;
+
+	writel(ch, priv->base +	OWL_UART_TXDAT);
+
+	return 0;
+}
+
+static int owl_serial_pending(struct udevice *dev, bool	input)
+{
+	struct owl_serial_priv *priv = dev_get_priv(dev);
+	unsigned int stat = readl(priv->base + OWL_UART_STAT);
+
+	if (input)
+		return !(stat &	OWL_UART_STAT_RFEM);
+	else
+		return !(stat &	OWL_UART_STAT_TFES);
+}
+
+static int owl_serial_probe(struct udevice *dev)
+{
+	struct owl_serial_priv *priv = dev_get_priv(dev);
+	struct clk clk;
+	u32 uart_ctl;
+	int ret;
+
+	/* Set data, parity and stop bits */
+	uart_ctl = readl(priv->base + OWL_UART_CTL);
+	uart_ctl &= ~(OWL_UART_CTL_PRS_NONE);
+	uart_ctl &= ~(OWL_UART_CTL_STPS);
+	uart_ctl |= OWL_UART_CTL_DWLS;
+	writel(uart_ctl, priv->base + OWL_UART_CTL);
+
+	/* Enable UART clock */
+	ret = clk_get_by_index(dev, 0, &clk);
+	if (ret < 0)
+		return ret;
+
+	ret = clk_enable(&clk);
+	if (ret < 0)
+		return ret;
+
+	return 0;
+}
+
+static int owl_serial_ofdata_to_platdata(struct	udevice	*dev)
+{
+	struct owl_serial_priv *priv = dev_get_priv(dev);
+
+	priv->base = dev_read_addr(dev);
+	if (priv->base == FDT_ADDR_T_NONE)
+		return -EINVAL;
+
+	return 0;
+}
+
+static const struct dm_serial_ops owl_serial_ops = {
+	.putc =	owl_serial_putc,
+	.pending = owl_serial_pending,
+	.getc =	owl_serial_getc,
+	.setbrg	= owl_serial_setbrg,
+};
+
+static const struct udevice_id owl_serial_ids[] = {
+	{ .compatible =	"actions,s900-serial" },
+	{ }
+};
+
+U_BOOT_DRIVER(serial_owl) = {
+	.name = "serial_owl",
+	.id = UCLASS_SERIAL,
+	.of_match = owl_serial_ids,
+	.ofdata_to_platdata = owl_serial_ofdata_to_platdata,
+	.priv_auto_alloc_size =	sizeof(struct owl_serial_priv),
+	.probe = owl_serial_probe,
+	.ops = &owl_serial_ops,
+	.flags = DM_FLAG_PRE_RELOC,
+};