The device has a highspeed register which influences the calcualtion of the
divisor. The chip lacks support for some baudrates. When requested, we set the
divisor to the next smaller baudrate and adjust the c_cflag accordingly.
Signed-off-by: Matthias Brugger <matthias....@gmail.com>
---
drivers/tty/serial/8250/8250_mtk.c | 294 ++++++++++++++++++++++++++++++++++++
drivers/tty/serial/8250/Kconfig | 7 +
drivers/tty/serial/8250/Makefile | 1 +
3 files changed, 302 insertions(+)
create mode 100644 drivers/tty/serial/8250/8250_mtk.c
diff --git a/drivers/tty/serial/8250/8250_mtk.c
b/drivers/tty/serial/8250/8250_mtk.c
new file mode 100644
index 0000000..1c4b4bf
--- /dev/null
+++ b/drivers/tty/serial/8250/8250_mtk.c
@@ -0,0 +1,294 @@
+/*
+ * Mediatek 8250 driver.
+ *
+ * Copyright (c) 2014 MundoReader S.L.
+ * Author: Matthias Brugger <matthias....@gmail.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_irq.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+#include <linux/pm_runtime.h>
+#include <linux/serial_8250.h>
+#include <linux/serial_reg.h>
+
+#include "8250.h"
+
+#define UART_MTK_HIGHS 0x09 /* Highspeed register */
+#define UART_MTK_SAMPLE_COUNT 0x0a /* Sample count register */
+#define UART_MTK_SAMPLE_POINT 0x0b /* Sample point register */
+#define MTK_UART_RATE_FIX 0x0d /* UART Rate Fix Register */
+
+struct mtk8250_data {
+ int line;
+ struct clk *clk;
+};
+
+static void
+mtk8250_set_termios(struct uart_port *port, struct ktermios *termios,
+ struct ktermios *old)
+{
+ unsigned long flags;
+ unsigned int baud, quot;
+
+ struct uart_8250_port *up =
+ container_of(port, struct uart_8250_port, port);
+
+ serial8250_do_set_termios(port, termios, old);
+
+ /*
+ * Mediatek UARTs use an extra highspeed register (UART_MTK_HIGHS)
+ *
+ * We need to recalcualte the quot register, as the claculation depends
+ * on the vaule in the highspeed register.
+ *
+ * Some baudrates are not supported by the chip, so we use the next
+ * lower rate supported and update termios c_flag.
+ *
+ * If highspeed register is set to 3, we need to specify sample count
+ * and sample point to increase accuracy. If not, we reset the
+ * registers to their default values.
+ */
+ baud = uart_get_baud_rate(port, termios, old,
+ port->uartclk / 16 / 0xffff,
+ port->uartclk / 16);
+
+ if (baud <= 115200) {
+ serial_port_out(port, UART_MTK_HIGHS, 0x0);
+ quot = uart_get_divisor(port, baud);
+ } else if (baud <= 576000) {
+ serial_port_out(port, UART_MTK_HIGHS, 0x2);
+
+ /* Set to next lower baudrate supported */
+ if ((baud == 500000) || (baud == 576000))
+ baud = 460800;
+ quot = DIV_ROUND_CLOSEST(port->uartclk, 4 * baud);
+ } else {
+ serial_port_out(port, UART_MTK_HIGHS, 0x3);
+
+ /* Set to highest baudrate supported */
+ if (baud >= 1152000)
+ baud = 921600;
+ quot = DIV_ROUND_CLOSEST(port->uartclk, 256 * baud);
+ }
+
+ /*
+ * Ok, we're now changing the port state. Do it with
+ * interrupts disabled.
+ */
+ spin_lock_irqsave(&port->lock, flags);
+
+ /* set DLAB we have cval saved in up->lcr from the call to the core */
+ serial_port_out(port, UART_LCR, up->lcr | UART_LCR_DLAB);
+ serial_dl_write(up, quot);
+
+ /* reset DLAB */
+ serial_port_out(port, UART_LCR, up->lcr);
+
+ if (baud > 460800) {
+ unsigned int tmp;
+
+ tmp = DIV_ROUND_CLOSEST(port->uartclk, quot * baud);
+ serial_port_out(port, UART_MTK_SAMPLE_COUNT, tmp - 1);
+ serial_port_out(port, UART_MTK_SAMPLE_POINT,
+ (tmp - 2) >> 1);
+ } else {
+ serial_port_out(port, UART_MTK_SAMPLE_COUNT, 0x00);
+ serial_port_out(port, UART_MTK_SAMPLE_POINT, 0xff);
+ }
+
+ spin_unlock_irqrestore(&port->lock, flags);
+ /* Don't rewrite B0 */
+ if (tty_termios_baud_rate(termios))
+ tty_termios_encode_baud_rate(termios, baud, baud);
+}
+
+static void
+mtk8250_do_pm(struct uart_port *port, unsigned int state, unsigned int old)
+{
+ if (!state)
+ pm_runtime_get_sync(port->dev);
+
+ serial8250_do_pm(port, state, old);
+
+ if (state)
+ pm_runtime_put_sync_suspend(port->dev);
+}
+
+static int mtk8250_probe_of(struct platform_device *pdev, struct uart_port *p,
+ struct mtk8250_data *data)
+{
+ int err;
+ struct device_node *np = pdev->dev.of_node;
+
+ data->clk = of_clk_get(np, 0);
+ if (IS_ERR(data->clk)) {
+ dev_warn(&pdev->dev, "Can't get timer clock\n");
+ return PTR_ERR(data->clk);
+ }
+
+ err = clk_prepare_enable(data->clk);
+ if (err) {
+ dev_warn(&pdev->dev, "Can't prepare clock\n");
+ clk_put(data->clk);
+ return err;
+ }
+ p->uartclk = clk_get_rate(data->clk);
+
+ return 0;
+}
+
+static int mtk8250_probe(struct platform_device *pdev)
+{
+ struct uart_8250_port uart = {};
+ struct resource *regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ struct resource *irq = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
+ struct mtk8250_data *data;
+ int err;
+
+ if (!regs || !irq) {
+ dev_err(&pdev->dev, "no registers/irq defined\n");
+ return -EINVAL;
+ }
+
+ uart.port.membase = devm_ioremap(&pdev->dev, regs->start,
+ resource_size(regs));
+ if (!uart.port.membase)
+ return -ENOMEM;
+
+ data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
+ if (!data)
+ return -ENOMEM;
+
+ if (pdev->dev.of_node) {
+ err = mtk8250_probe_of(pdev, &uart.port, data);
+ if (err)
+ return err;
+ } else
+ return -ENODEV;
+
+ spin_lock_init(&uart.port.lock);
+ uart.port.mapbase = regs->start;
+ uart.port.irq = irq->start;
+ uart.port.pm = mtk8250_do_pm;
+ uart.port.type = PORT_16550;
+ uart.port.flags = UPF_BOOT_AUTOCONF | UPF_FIXED_PORT;
+ uart.port.dev = &pdev->dev;
+ uart.port.iotype = UPIO_MEM32;
+ uart.port.regshift = 2;
+ uart.port.private_data = data;
+ uart.port.set_termios = mtk8250_set_termios;
+
+ /* Disable Rate Fix function */
+ writel(0x0, uart.port.membase +
+ (MTK_UART_RATE_FIX << uart.port.regshift));
+
+ data->line = serial8250_register_8250_port(&uart);
+ if (data->line < 0)
+ return data->line;
+
+ platform_set_drvdata(pdev, data);
+
+ pm_runtime_set_active(&pdev->dev);
+ pm_runtime_enable(&pdev->dev);
+
+ return 0;
+}
+
+static int mtk8250_remove(struct platform_device *pdev)
+{
+ struct mtk8250_data *data = platform_get_drvdata(pdev);
+
+ pm_runtime_get_sync(&pdev->dev);
+
+ serial8250_unregister_port(data->line);
+ if (!IS_ERR(data->clk)) {
+ clk_disable_unprepare(data->clk);
+ clk_put(data->clk);
+ }
+
+ pm_runtime_disable(&pdev->dev);
+ pm_runtime_put_noidle(&pdev->dev);
+ return 0;
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int mtk8250_suspend(struct device *dev)
+{
+ struct mtk8250_data *data = dev_get_drvdata(dev);
+
+ serial8250_suspend_port(data->line);
+
+ return 0;
+}
+
+static int mtk8250_resume(struct device *dev)
+{
+ struct mtk8250_data *data = dev_get_drvdata(dev);
+
+ serial8250_resume_port(data->line);
+
+ return 0;
+}
+#endif /* CONFIG_PM_SLEEP */
+
+#ifdef CONFIG_PM_RUNTIME
+static int mtk8250_runtime_suspend(struct device *dev)
+{
+ struct mtk8250_data *data = dev_get_drvdata(dev);
+
+ if (!IS_ERR(data->clk))
+ clk_disable_unprepare(data->clk);
+
+ return 0;
+}
+
+static int mtk8250_runtime_resume(struct device *dev)
+{
+ struct mtk8250_data *data = dev_get_drvdata(dev);
+
+ if (!IS_ERR(data->clk))
+ clk_prepare_enable(data->clk);
+
+ return 0;
+}
+#endif
+
+static const struct dev_pm_ops mtk8250_pm_ops = {
+ SET_SYSTEM_SLEEP_PM_OPS(mtk8250_suspend, mtk8250_resume)
+ SET_RUNTIME_PM_OPS(mtk8250_runtime_suspend, mtk8250_runtime_resume,
+ NULL)
+};
+
+static const struct of_device_id mtk8250_of_match[] = {
+ { .compatible = "mediatek,mt6577-uart" },
+ { /* Sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, mtk8250_of_match);
+
+static struct platform_driver mtk8250_platform_driver = {
+ .driver = {
+ .name = "mt6577-uart",
+ .pm = &mtk8250_pm_ops,
+ .of_match_table = mtk8250_of_match,
+ },
+ .probe = mtk8250_probe,
+ .remove = mtk8250_remove,
+};
+module_platform_driver(mtk8250_platform_driver);
+
+MODULE_AUTHOR("Matthias Brugger");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Mediatek 8250 serial port driver");
diff --git a/drivers/tty/serial/8250/Kconfig b/drivers/tty/serial/8250/Kconfig
index 349ee59..fac34aa 100644
--- a/drivers/tty/serial/8250/Kconfig
+++ b/drivers/tty/serial/8250/Kconfig
@@ -298,3 +298,10 @@ config SERIAL_8250_RT288X
If you have a Ralink RT288x/RT305x SoC based board and want to use the
serial port, say Y to this option. The driver can handle up to 2
serial
ports. If unsure, say N.
+
+config SERIAL_8250_MT6577
+ bool "Mediatek serial port support"
+ depends on SERIAL_8250 && ARCH_MEDIATEK
+ help
+ If you have a Mediatek based board and want to use the
+ serial port, say Y to this option. If unsure, say N.
diff --git a/drivers/tty/serial/8250/Makefile b/drivers/tty/serial/8250/Makefile
index 36d68d0..6dcb46b 100644
--- a/drivers/tty/serial/8250/Makefile
+++ b/drivers/tty/serial/8250/Makefile
@@ -20,3 +20,4 @@ obj-$(CONFIG_SERIAL_8250_HUB6) += 8250_hub6.o
obj-$(CONFIG_SERIAL_8250_FSL) += 8250_fsl.o
obj-$(CONFIG_SERIAL_8250_DW) += 8250_dw.o
obj-$(CONFIG_SERIAL_8250_EM) += 8250_em.o
+obj-$(CONFIG_SERIAL_8250_MT6577) += 8250_mtk.o
--
1.7.9.5
--
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