[PATCH v5] serial: 8250_uniphier: add UniPhier serial driver

From: Masahiro Yamada
Date: Sun May 24 2015 - 22:39:22 EST

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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@xxxxxxxxxxxxx>
Reviewed-by: Matthias Brugger <matthias.bgg@xxxxxxxxx>
---

Changes in v5:
- Set up.port.mapsize
- Pass NULL rahter than 0 to the second argument of devm_clk_get()

Changes in v4:
- Use spin_lock for read-modify-write register access
- Add /* fall through */ comments where I intentionally
did not add "break";
- Drop unnecessary #include <linux/serial_core.h>
- Drop unnecessary #include <linux/serial_reg.h>
- Add an empty line between #include <> and ""
- Use platform_get_irq() instead of platform_get_resource()

Changes in v3:
- Just add *_SHIFT macro for the special case

Changes in v2:
- Drop unnecessary #include <linux/init.h>
- Sort includes in alphabetical order
- Use devm_clk_get() rather than of_clk_get()
- Delete unneeded clk_put() from uniphier_uart_remove callback
- Delete unneeded IS_ERR_OR_NULL check from uniphier_uart_remove callback
- Use UNIPHIER_UART_*_SHIFT instead of hard-coded shift values
- Change the first argument type of uniphier_of_serial_setup()
from (struct platform_device *) to (struct device *) for code-cleanup.

drivers/tty/serial/8250/8250_uniphier.c | 258 ++++++++++++++++++++++++++++++++
drivers/tty/serial/8250/Kconfig | 7 +
drivers/tty/serial/8250/Makefile | 1 +
3 files changed, 266 insertions(+)
create mode 100644 drivers/tty/serial/8250/8250_uniphier.c

diff --git a/drivers/tty/serial/8250/8250_uniphier.c b/drivers/tty/serial/8250/8250_uniphier.c
new file mode 100644
index 0000000..13cc66b
--- /dev/null
+++ b/drivers/tty/serial/8250/8250_uniphier.c
@@ -0,0 +1,258 @@
+/*
+ * Copyright (C) 2015 Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
+ *
+ * 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 <linux/serial_8250.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)
+{
+ 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)
+{
+ 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@xxxxxxxxxxxxx>");
+MODULE_DESCRIPTION("UniPhier UART driver");
+MODULE_LICENSE("GPL");
diff --git a/drivers/tty/serial/8250/Kconfig b/drivers/tty/serial/8250/Kconfig
index c350703..3e1ae446 100644
--- a/drivers/tty/serial/8250/Kconfig
+++ b/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.
diff --git a/drivers/tty/serial/8250/Makefile b/drivers/tty/serial/8250/Makefile
index 31e7cdc..f7ca8c3 100644
--- a/drivers/tty/serial/8250/Makefile
+++ b/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
--
1.9.1

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Next message: Jisheng Zhang: "Re: [PATCH v2] i2c: designware: Avoid unnecessary resuming during system suspend"
Previous message: Shailendra Verma: "[PATCH] base:cacheinfo - Fix for typos in comment and pr_warn log message"
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