Message-ID: <1432545245.8736.5.camel@intel.com>
Date:	Mon, 25 May 2015 09:14:06 +0000
From:	"Shevchenko, Andriy" <andriy.shevchenko@...el.com>
To:	"yamada.masahiro@...ionext.com" <yamada.masahiro@...ionext.com>
CC:	"manabian@...il.com" <manabian@...il.com>,
	"bigeasy@...utronix.de" <bigeasy@...utronix.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"alan@...rguk.ukuu.org.uk" <alan@...rguk.ukuu.org.uk>,
	"ricardo.ribalda@...il.com" <ricardo.ribalda@...il.com>,
	"alan@...ux.intel.com" <alan@...ux.intel.com>,
	"blogic@...nwrt.org" <blogic@...nwrt.org>,
	"linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"jslaby@...e.cz" <jslaby@...e.cz>,
	"matthias.bgg@...il.com" <matthias.bgg@...il.com>,
	"peter@...leysoftware.com" <peter@...leysoftware.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v6] serial: 8250_uniphier: add UniPhier serial driver

On Mon, 2015-05-25 at 12:44 +0900, Masahiro Yamada wrote:
> 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.

Do not send series too often, let people to review what you did.

More comments below.

> 
> Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>
> Reviewed-by: Matthias Brugger <matthias.bgg@...il.com>
> ---
> 
> Changes in v6:
>   - Drop unnecessary #include <linux/serial_8250.h>
>     (it is covered by #include "8250.h")
> 
> 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 | 257 ++++++++++++++++++++++++++++++++
>  drivers/tty/serial/8250/Kconfig         |   7 +
>  drivers/tty/serial/8250/Makefile        |   1 +
>  3 files changed, 265 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..6f1e997
> --- /dev/null
> +++ b/drivers/tty/serial/8250/8250_uniphier.c
> @@ -0,0 +1,257 @@
> +/*
> + * Copyright (C) 2015 Masahiro Yamada <yamada.masahiro@...ionext.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

Indentation problem, needs to be fixed.

> +#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;

Perhaps unsigned int?

> +
> +	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;

Ditto.

> +	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);

Perhaps put this in place where normal == true and use return instead of
break?

> +	} 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@...ionext.com>");
> +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


-- 
Andy Shevchenko <andriy.shevchenko@...el.com>
Intel Finland Oy
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