[PATCH v2 0/2] tty: serial: Add mediatek UART driver

[PATCH v2 0/2] tty: serial: Add mediatek UART driver

[Matthias Brugger]

This patch set adds support for the UART found in Mediatek SoCs.
The chip is a changed version of a 8250 controller.
Especially it introduces a new register called highspeed. The value
in this register has to be set depending on the baudrate. The value
in the register influences the way the divisor has to be calculated.

The patch series is build against v3.16-rc1 and tested on mt6589. Should
work as well on mt6577 and mt6582.

Thanks,
Matthias

Changes for v2:
- drop 8250_core capability extension for the chip
- encapsulate set_termios in the driver method

Matthias Brugger (2):
  tty: serial: 8250: Add Mediatek UART driver
  DTS: serial: Add bindings documention for the Mediatek UARTs

 .../devicetree/bindings/serial/mtk-uart.txt        |   19 ++
 drivers/tty/serial/8250/8250_mtk.c                 |  302 ++++++++++++++++++++
 drivers/tty/serial/8250/Kconfig                    |    7 +
 drivers/tty/serial/8250/Makefile                   |    1 +
 4 files changed, 329 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/serial/mtk-uart.txt
 create mode 100644 drivers/tty/serial/8250/8250_mtk.c

-- 
1.7.9.5

[PATCH v2 1/2] tty: serial: 8250: Add Mediatek UART driver

[Matthias Brugger]

This patch adds support for the UART block found on Mediatek SoCs.
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.bgg@gmail.com>
---
 drivers/tty/serial/8250/8250_mtk.c |  302 ++++++++++++++++++++++++++++++++++++
 drivers/tty/serial/8250/Kconfig    |    7 +
 drivers/tty/serial/8250/Makefile   |    1 +
 3 files changed, 310 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..038d7e2
--- /dev/null
+++ b/drivers/tty/serial/8250/8250_mtk.c
@@ -0,0 +1,302 @@
+/*
+ * Mediatek 8250 driver.
+ *
+ * Copyright (c) 2014 MundoReader S.L.
+ * Author: Matthias Brugger <matthias.bgg@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 */
+
+#define SET_CFLAG_BAUD(flag, baud) { \
+		(flag) &= ~CBAUD; \
+		(flag) |= (baud); \
+	}
+
+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;
+			SET_CFLAG_BAUD(termios->c_cflag, B460800);
+		}
+		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;
+			SET_CFLAG_BAUD(termios->c_cflag, B921600);
+		}
+		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);
+}
+
+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 uart_port *p,
+			   struct mtk8250_data *data)
+{
+	int err;
+	struct device_node	*np = p->dev->of_node;
+
+	data->clk = of_clk_get(np, 0);
+	if (IS_ERR(data->clk)) {
+		pr_warn("Can't get timer clock");
+		return PTR_ERR(data->clk);
+	}
+
+	err = clk_prepare_enable(data->clk);
+	if (err) {
+		pr_warn("Can't prepare clock");
+		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;
+	}
+
+	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.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;
+
+	uart.port.iotype = UPIO_MEM32;
+	uart.port.regshift = 2;
+	uart.port.private_data = data;
+	uart.port.set_termios = mtk8250_set_termios;
+
+	if (pdev->dev.of_node) {
+		err = mtk8250_probe_of(&uart.port, data);
+		if (err)
+			return err;
+	} else
+		return -ENODEV;
+
+	/* 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",
+		.owner		= THIS_MODULE,
+		.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

[PATCH v2 2/2] DTS: serial: Add bindings documention for the Mediatek UARTs

[Matthias Brugger]

This patch adds the devicetree documentation for the Mediatek UART.

Signed-off-by: Matthias Brugger <matthias.bgg-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
---
 .../devicetree/bindings/serial/mtk-uart.txt        |   19 +++++++++++++++++++
 1 file changed, 19 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/serial/mtk-uart.txt

diff --git a/Documentation/devicetree/bindings/serial/mtk-uart.txt b/Documentation/devicetree/bindings/serial/mtk-uart.txt
new file mode 100644
index 0000000..2bf571e
--- /dev/null
+++ b/Documentation/devicetree/bindings/serial/mtk-uart.txt
@@ -0,0 +1,19 @@
+* Mediatek Universal Asynchronous Receiver/Transmitter (UART)
+
+- compatible: "mediatek,mt6577-uart"
+  Compatibility with mt6577, mt6589, mt6582
+
+- reg: The base address of the UART register bank.
+
+- interrupts: A single interrupt specifier.
+
+- clocks: Clock driving the hardware.
+
+Example:
+
+	uart0: serial@11006000 {
+		compatible = "mediatek,mt6577-uart";
+		reg = <0x11006000 0x400>;
+		interrupts = <GIC_SPI 51 IRQ_TYPE_LEVEL_LOW>;
+		clocks = <&uart_clk>;
+	};
-- 
1.7.9.5

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Re: [PATCH v2 1/2] tty: serial: 8250: Add Mediatek UART driver

[Alan Cox]

> +	 * Some baudrates are not supported by the chip, so we use the next
> +	 * lower rate supported and update termios c_flag.

I don't see the termios updating being done now ?

> +	data->clk = of_clk_get(np, 0);
> +	if (IS_ERR(data->clk)) {
> +		pr_warn("Can't get timer clock");
> +		return PTR_ERR(data->clk);
> +	}
> +
> +	err = clk_prepare_enable(data->clk);
> +	if (err) {
> +		pr_warn("Can't prepare clock");

and these do need a newline on them. They are also not very useful as
they don't indicate what device was involved. If you passed pdev from
mtk8250_probe you'd be able to use dev_warn instead

Otherwise looks great and exactly as 8250_core is intended to be used.

Alan


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Re: [PATCH v2 1/2] tty: serial: 8250: Add Mediatek UART driver

[Matthias Brugger]

2014-08-07 15:21 GMT+02:00 Alan Cox <alan@linux.intel.com>:
>
>> +      * Some baudrates are not supported by the chip, so we use the next
>> +      * lower rate supported and update termios c_flag.
>
> I don't see the termios updating being done now ?

Please have a look on the usage of the SET_CFLAG_BAUD macro in the patch.
I'm not sure if it is the way to go though.

>
>> +     data->clk = of_clk_get(np, 0);
>> +     if (IS_ERR(data->clk)) {
>> +             pr_warn("Can't get timer clock");
>> +             return PTR_ERR(data->clk);
>> +     }
>> +
>> +     err = clk_prepare_enable(data->clk);
>> +     if (err) {
>> +             pr_warn("Can't prepare clock");
>
> and these do need a newline on them. They are also not very useful as
> they don't indicate what device was involved. If you passed pdev from
> mtk8250_probe you'd be able to use dev_warn instead
>
> Otherwise looks great and exactly as 8250_core is intended to be used.
>
> Alan
>
>



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Re: [PATCH v2 1/2] tty: serial: 8250: Add Mediatek UART driver

[One Thousand Gnomes]

On Thu, 7 Aug 2014 16:07:41 +0200
Matthias Brugger <matthias.bgg@gmail.com> wrote:

> 2014-08-07 15:21 GMT+02:00 Alan Cox <alan@linux.intel.com>:
> >
> >> +      * Some baudrates are not supported by the chip, so we use the next
> >> +      * lower rate supported and update termios c_flag.
> >
> > I don't see the termios updating being done now ?
> 
> Please have a look on the usage of the SET_CFLAG_BAUD macro in the patch.
> I'm not sure if it is the way to go though.

Ah missed that - no it's not the right way to go. From
8250_core:serial8250_do_set_termios() do

        /* Don't rewrite B0 */
        if (tty_termios_baud_rate(termios))
                tty_termios_encode_baud_rate(termios, baud, baud);


which will encoding the baud rate correctly for all cases, and where
possible encode it in the old style format rather than using BOTHER
(which old old apps cannot handle)

Alan