serial: 8250_uniphier: add UniPhier serial driver

Add the driver for on-chip UART used on UniPhier SoCs.

This hardware is similar to 8250, but the register mapping is
slightly different:
  - The offset to FCR, MCR is different.
  - The divisor latch access bit does not exist.  Instead, the
    divisor latch register is available at offset 9.

This driver overrides serial_{in,out}, dl_{read,write} callbacks,
but wants to borrow most of code from 8250_core.c.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/8250/8250_uniphier.c

+/*
+ * Copyright (C) 2015 Masahiro Yamada <yamada.masahiro@socionext.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/clk.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+
+#include "8250.h"
+
+/* Most (but not all) of UniPhier UART devices have 64-depth FIFO. */
+#define UNIPHIER_UART_DEFAULT_FIFO_SIZE	64
+
+#define UNIPHIER_UART_CHAR_FCR	3	/* Character / FIFO Control Register */
+#define UNIPHIER_UART_LCR_MCR	4	/* Line/Modem Control Register */
+#define   UNIPHIER_UART_LCR_SHIFT	8
+#define UNIPHIER_UART_DLR	9	/* Divisor Latch Register */
+
+struct uniphier8250_priv {
+	int line;
+	struct clk *clk;
+	spinlock_t atomic_write_lock;
+};
+
+/*
+ * The register map is slightly different from that of 8250.
+ * IO callbacks must be overridden for correct access to FCR, LCR, and MCR.
+ */
+static unsigned int uniphier_serial_in(struct uart_port *p, int offset)
+{
+	unsigned int valshift = 0;
+
+	switch (offset) {
+	case UART_LCR:
+		valshift = UNIPHIER_UART_LCR_SHIFT;
+		/* fall through */
+	case UART_MCR:
+		offset = UNIPHIER_UART_LCR_MCR;
+		break;
+	default:
+		break;
+	}
+
+	offset <<= p->regshift;
+
+	/*
+	 * The return value must be masked with 0xff because LCR and MCR reside
+	 * in the same register that must be accessed by 32-bit write/read.
+	 * 8 or 16 bit access to this hardware result in unexpected behavior.
+	 */
+	return (readl(p->membase + offset) >> valshift) & 0xff;
+}
+
+static void uniphier_serial_out(struct uart_port *p, int offset, int value)
+{
+	unsigned int valshift = 0;
+	bool normal = false;
+
+	switch (offset) {
+	case UART_FCR:
+		offset = UNIPHIER_UART_CHAR_FCR;
+		break;
+	case UART_LCR:
+		valshift = UNIPHIER_UART_LCR_SHIFT;
+		/* Divisor latch access bit does not exist. */
+		value &= ~(UART_LCR_DLAB << valshift);
+		/* fall through */
+	case UART_MCR:
+		offset = UNIPHIER_UART_LCR_MCR;
+		break;
+	default:
+		normal = true;
+		break;
+	}
+
+	offset <<= p->regshift;
+
+	if (normal) {
+		writel(value, p->membase + offset);
+	} else {
+		/*
+		 * Special case: two registers share the same address that
+		 * must be 32-bit accessed.  As this is not longer atomic safe,
+		 * take a lock just in case.
+		 */
+		struct uniphier8250_priv *priv = p->private_data;
+		unsigned long flags;
+		u32 tmp;
+
+		spin_lock_irqsave(&priv->atomic_write_lock, flags);
+		tmp = readl(p->membase + offset);
+		tmp &= ~(0xff << valshift);
+		tmp |= value << valshift;
+		writel(tmp, p->membase + offset);
+		spin_unlock_irqrestore(&priv->atomic_write_lock, flags);
+	}
+}
+
+/*
+ * This hardware does not have the divisor latch access bit.
+ * The divisor latch register exists at different address.
+ * Override dl_read/write callbacks.
+ */
+static int uniphier_serial_dl_read(struct uart_8250_port *up)
+{
+	return readl(up->port.membase + UNIPHIER_UART_DLR);
+}
+
+static void uniphier_serial_dl_write(struct uart_8250_port *up, int value)
+{
+	writel(value, up->port.membase + UNIPHIER_UART_DLR);
+}
+
+static int uniphier_of_serial_setup(struct device *dev, struct uart_port *port,
+				    struct uniphier8250_priv *priv)
+{
+	int ret;
+	u32 prop;
+	struct device_node *np = dev->of_node;
+
+	ret = of_alias_get_id(np, "serial");
+	if (ret < 0) {
+		dev_err(dev, "failed to get alias id\n");
+		return ret;
+	}
+	port->line = priv->line = ret;
+
+	/* Get clk rate through clk driver */
+	priv->clk = devm_clk_get(dev, NULL);
+	if (IS_ERR(priv->clk)) {
+		dev_err(dev, "failed to get clock\n");
+		return PTR_ERR(priv->clk);
+	}
+
+	ret = clk_prepare_enable(priv->clk);
+	if (ret < 0)
+		return ret;
+
+	port->uartclk = clk_get_rate(priv->clk);
+
+	/* Check for fifo size */
+	if (of_property_read_u32(np, "fifo-size", &prop) == 0)
+		port->fifosize = prop;
+	else
+		port->fifosize = UNIPHIER_UART_DEFAULT_FIFO_SIZE;
+
+	return 0;
+}
+
+static int uniphier_uart_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct uart_8250_port up;
+	struct uniphier8250_priv *priv;
+	struct resource *regs;
+	void __iomem *membase;
+	int irq;
+	int ret;
+
+	regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!regs) {
+		dev_err(dev, "failed to get memory resource");
+		return -EINVAL;
+	}
+
+	membase = devm_ioremap(dev, regs->start, resource_size(regs));
+	if (!membase)
+		return -ENOMEM;
+
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0) {
+		dev_err(dev, "failed to get IRQ number");
+		return irq;
+	}
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	memset(&up, 0, sizeof(up));
+
+	ret = uniphier_of_serial_setup(dev, &up.port, priv);
+	if (ret < 0)
+		return ret;
+
+	spin_lock_init(&priv->atomic_write_lock);
+
+	up.port.dev = dev;
+	up.port.private_data = priv;
+	up.port.mapbase = regs->start;
+	up.port.mapsize = resource_size(regs);
+	up.port.membase = membase;
+	up.port.irq = irq;
+
+	up.port.type = PORT_16550A;
+	up.port.iotype = UPIO_MEM32;
+	up.port.regshift = 2;
+	up.port.flags = UPF_FIXED_PORT | UPF_FIXED_TYPE;
+	up.capabilities = UART_CAP_FIFO;
+
+	up.port.serial_in = uniphier_serial_in;
+	up.port.serial_out = uniphier_serial_out;
+	up.dl_read = uniphier_serial_dl_read;
+	up.dl_write = uniphier_serial_dl_write;
+
+	ret = serial8250_register_8250_port(&up);
+	if (ret < 0) {
+		dev_err(dev, "failed to register 8250 port\n");
+		return ret;
+	}
+
+	platform_set_drvdata(pdev, priv);
+
+	return 0;
+}
+
+static int uniphier_uart_remove(struct platform_device *pdev)
+{
+	struct uniphier8250_priv *priv = platform_get_drvdata(pdev);
+
+	serial8250_unregister_port(priv->line);
+	clk_disable_unprepare(priv->clk);
+
+	return 0;
+}
+
+static const struct of_device_id uniphier_uart_match[] = {
+	{ .compatible = "socionext,uniphier-uart" },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, uniphier_uart_match);
+
+static struct platform_driver uniphier_uart_platform_driver = {
+	.probe		= uniphier_uart_probe,
+	.remove		= uniphier_uart_remove,
+	.driver = {
+		.name	= "uniphier-uart",
+		.of_match_table = uniphier_uart_match,
+	},
+};
+module_platform_driver(uniphier_uart_platform_driver);
+
+MODULE_AUTHOR("Masahiro Yamada <yamada.masahiro@socionext.com>");
+MODULE_DESCRIPTION("UniPhier UART driver");
+MODULE_LICENSE("GPL");

drivers/tty/serial/8250/Kconfig

@@ -342,3 +342,10 @@ config SERIAL_8250_MT6577
 	help
 	  If you have a Mediatek based board and want to use the
 	  serial port, say Y to this option. If unsure, say N.
+
+config SERIAL_8250_UNIPHIER
+	tristate "Support for UniPhier on-chip UART"
+	depends on SERIAL_8250 && ARCH_UNIPHIER
+	help
+	  If you have a UniPhier based board and want to use the on-chip
+	  serial ports, say Y to this option. If unsure, say N.

drivers/tty/serial/8250/Makefile

@@ -23,3 +23,4 @@ obj-$(CONFIG_SERIAL_8250_EM)		+= 8250_em.o
 obj-$(CONFIG_SERIAL_8250_OMAP)		+= 8250_omap.o
 obj-$(CONFIG_SERIAL_8250_FINTEK)	+= 8250_fintek.o
 obj-$(CONFIG_SERIAL_8250_MT6577)	+= 8250_mtk.o
+obj-$(CONFIG_SERIAL_8250_UNIPHIER)	+= 8250_uniphier.o