drivers/serial: Add driver for Aspeed virtual UART

What:		/sys/bus/platform/drivers/aspeed-vuart/*/lpc_address

Date:		April 2017

Contact:	Jeremy Kerr <jk@ozlabs.org>

Description:	Configures which IO port the host side of the UART

		will appear on the host <-> BMC LPC bus.

Users:		OpenBMC.  Proposed changes should be mailed to

		openbmc@lists.ozlabs.org

What:		/sys/bus/platform/drivers/aspeed-vuart*/sirq

Date:		April 2017

Contact:	Jeremy Kerr <jk@ozlabs.org>

Description:	Configures which interrupt number the host side of

		the UART will appear on the host <-> BMC LPC bus.

Users:		OpenBMC.  Proposed changes should be mailed to

		openbmc@lists.ozlabs.org

	- "fsl,16550-FIFO64"

	- "fsl,ns16550"

	- "ti,da830-uart"

	- "aspeed,ast2400-vuart"

	- "aspeed,ast2500-vuart"

	- "serial" if the port type is unknown.

- reg : offset and length of the register set for the device.

- interrupts : should contain uart interrupt.

/*

 *  Serial Port driver for Aspeed VUART device

 *

 *    Copyright (C) 2016 Jeremy Kerr <jk@ozlabs.org>, IBM Corp.

 *    Copyright (C) 2006 Arnd Bergmann <arnd@arndb.de>, IBM Corp.

 *

 *  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.

 */

#include <linux/device.h>

#include <linux/module.h>

#include <linux/of_address.h>

#include <linux/of_irq.h>

#include <linux/of_platform.h>

#include <linux/clk.h>

#include "8250.h"

#define ASPEED_VUART_GCRA		0x20

#define ASPEED_VUART_GCRA_VUART_EN		BIT(0)

#define ASPEED_VUART_GCRA_DISABLE_HOST_TX_DISCARD BIT(5)

#define ASPEED_VUART_GCRB		0x24

#define ASPEED_VUART_GCRB_HOST_SIRQ_MASK	GENMASK(7, 4)

#define ASPEED_VUART_GCRB_HOST_SIRQ_SHIFT	4

#define ASPEED_VUART_ADDRL		0x28

#define ASPEED_VUART_ADDRH		0x2c

struct aspeed_vuart {

	struct device		*dev;

	void __iomem		*regs;

	struct clk		*clk;

	int			line;

};

/*

 * The VUART is basically two UART 'front ends' connected by their FIFO

 * (no actual serial line in between). One is on the BMC side (management

 * controller) and one is on the host CPU side.

 *

 * It allows the BMC to provide to the host a "UART" that pipes into

 * the BMC itself and can then be turned by the BMC into a network console

 * of some sort for example.

 *

 * This driver is for the BMC side. The sysfs files allow the BMC

 * userspace which owns the system configuration policy, to specify

 * at what IO port and interrupt number the host side will appear

 * to the host on the Host <-> BMC LPC bus. It could be different on a

 * different system (though most of them use 3f8/4).

 */

static ssize_t lpc_address_show(struct device *dev,

				struct device_attribute *attr, char *buf)

{

	struct aspeed_vuart *vuart = dev_get_drvdata(dev);

	u16 addr;

	addr = (readb(vuart->regs + ASPEED_VUART_ADDRH) << 8) |

		(readb(vuart->regs + ASPEED_VUART_ADDRL));

	return snprintf(buf, PAGE_SIZE - 1, "0x%x\n", addr);

}

static ssize_t lpc_address_store(struct device *dev,

				 struct device_attribute *attr,

				 const char *buf, size_t count)

{

	struct aspeed_vuart *vuart = dev_get_drvdata(dev);

	unsigned long val;

	int err;

	err = kstrtoul(buf, 0, &val);

	if (err)

		return err;

	writeb(val >> 8, vuart->regs + ASPEED_VUART_ADDRH);

	writeb(val >> 0, vuart->regs + ASPEED_VUART_ADDRL);

	return count;

}

static DEVICE_ATTR_RW(lpc_address);

static ssize_t sirq_show(struct device *dev,

			 struct device_attribute *attr, char *buf)

{

	struct aspeed_vuart *vuart = dev_get_drvdata(dev);

	u8 reg;

	reg = readb(vuart->regs + ASPEED_VUART_GCRB);

	reg &= ASPEED_VUART_GCRB_HOST_SIRQ_MASK;

	reg >>= ASPEED_VUART_GCRB_HOST_SIRQ_SHIFT;

	return snprintf(buf, PAGE_SIZE - 1, "%u\n", reg);

}

static ssize_t sirq_store(struct device *dev, struct device_attribute *attr,

			  const char *buf, size_t count)

{

	struct aspeed_vuart *vuart = dev_get_drvdata(dev);

	unsigned long val;

	int err;

	u8 reg;

	err = kstrtoul(buf, 0, &val);

	if (err)

		return err;

	val <<= ASPEED_VUART_GCRB_HOST_SIRQ_SHIFT;

	val &= ASPEED_VUART_GCRB_HOST_SIRQ_MASK;

	reg = readb(vuart->regs + ASPEED_VUART_GCRB);

	reg &= ~ASPEED_VUART_GCRB_HOST_SIRQ_MASK;

	reg |= val;

	writeb(reg, vuart->regs + ASPEED_VUART_GCRB);

	return count;

}

static DEVICE_ATTR_RW(sirq);

static struct attribute *aspeed_vuart_attrs[] = {

	&dev_attr_sirq.attr,

	&dev_attr_lpc_address.attr,

	NULL,

};

static const struct attribute_group aspeed_vuart_attr_group = {

	.attrs = aspeed_vuart_attrs,

};

static void aspeed_vuart_set_enabled(struct aspeed_vuart *vuart, bool enabled)

{

	u8 reg = readb(vuart->regs + ASPEED_VUART_GCRA);

	if (enabled)

		reg |= ASPEED_VUART_GCRA_VUART_EN;

	else

		reg &= ~ASPEED_VUART_GCRA_VUART_EN;

	writeb(reg, vuart->regs + ASPEED_VUART_GCRA);

}

static void aspeed_vuart_set_host_tx_discard(struct aspeed_vuart *vuart,

					     bool discard)

{

	u8 reg;

	reg = readb(vuart->regs + ASPEED_VUART_GCRA);

	/* If the DISABLE_HOST_TX_DISCARD bit is set, discard is disabled */

	if (!discard)

		reg |= ASPEED_VUART_GCRA_DISABLE_HOST_TX_DISCARD;

	else

		reg &= ~ASPEED_VUART_GCRA_DISABLE_HOST_TX_DISCARD;

	writeb(reg, vuart->regs + ASPEED_VUART_GCRA);

}

static int aspeed_vuart_startup(struct uart_port *uart_port)

{

	struct uart_8250_port *uart_8250_port = up_to_u8250p(uart_port);

	struct aspeed_vuart *vuart = uart_8250_port->port.private_data;

	int rc;

	rc = serial8250_do_startup(uart_port);

	if (rc)

		return rc;

	aspeed_vuart_set_host_tx_discard(vuart, false);

	return 0;

}

static void aspeed_vuart_shutdown(struct uart_port *uart_port)

{

	struct uart_8250_port *uart_8250_port = up_to_u8250p(uart_port);

	struct aspeed_vuart *vuart = uart_8250_port->port.private_data;

	aspeed_vuart_set_host_tx_discard(vuart, true);

	serial8250_do_shutdown(uart_port);

}

static int aspeed_vuart_probe(struct platform_device *pdev)

{

	struct uart_8250_port port;

	struct aspeed_vuart *vuart;

	struct device_node *np;

	struct resource *res;

	u32 clk, prop;

	int rc;

	np = pdev->dev.of_node;

	vuart = devm_kzalloc(&pdev->dev, sizeof(*vuart), GFP_KERNEL);

	if (!vuart)

		return -ENOMEM;

	vuart->dev = &pdev->dev;

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);

	vuart->regs = devm_ioremap_resource(&pdev->dev, res);

	if (IS_ERR(vuart->regs))

		return PTR_ERR(vuart->regs);

	memset(&port, 0, sizeof(port));

	port.port.private_data = vuart;

	port.port.membase = vuart->regs;

	port.port.mapbase = res->start;

	port.port.mapsize = resource_size(res);

	port.port.startup = aspeed_vuart_startup;

	port.port.shutdown = aspeed_vuart_shutdown;

	port.port.dev = &pdev->dev;

	rc = sysfs_create_group(&vuart->dev->kobj, &aspeed_vuart_attr_group);

	if (rc < 0)

		return rc;

	if (of_property_read_u32(np, "clock-frequency", &clk)) {

		vuart->clk = devm_clk_get(&pdev->dev, NULL);

		if (IS_ERR(vuart->clk)) {

			dev_warn(&pdev->dev,

				"clk or clock-frequency not defined\n");

			return PTR_ERR(vuart->clk);

		}

		rc = clk_prepare_enable(vuart->clk);

		if (rc < 0)

			return rc;

		clk = clk_get_rate(vuart->clk);

	}

	/* If current-speed was set, then try not to change it. */

	if (of_property_read_u32(np, "current-speed", &prop) == 0)

		port.port.custom_divisor = clk / (16 * prop);

	/* Check for shifted address mapping */

	if (of_property_read_u32(np, "reg-offset", &prop) == 0)

		port.port.mapbase += prop;

	/* Check for registers offset within the devices address range */

	if (of_property_read_u32(np, "reg-shift", &prop) == 0)

		port.port.regshift = prop;

	/* Check for fifo size */

	if (of_property_read_u32(np, "fifo-size", &prop) == 0)

		port.port.fifosize = prop;

	/* Check for a fixed line number */

	rc = of_alias_get_id(np, "serial");

	if (rc >= 0)

		port.port.line = rc;

	port.port.irq = irq_of_parse_and_map(np, 0);

	port.port.irqflags = IRQF_SHARED;

	port.port.iotype = UPIO_MEM;

	port.port.type = PORT_16550A;

	port.port.uartclk = clk;

	port.port.flags = UPF_SHARE_IRQ | UPF_BOOT_AUTOCONF

		| UPF_FIXED_PORT | UPF_FIXED_TYPE | UPF_NO_THRE_TEST;

	if (of_property_read_bool(np, "no-loopback-test"))

		port.port.flags |= UPF_SKIP_TEST;

	if (port.port.fifosize)

		port.capabilities = UART_CAP_FIFO;

	if (of_property_read_bool(np, "auto-flow-control"))

		port.capabilities |= UART_CAP_AFE;

	rc = serial8250_register_8250_port(&port);

	if (rc < 0)

		goto err_clk_disable;

	vuart->line = rc;

	aspeed_vuart_set_enabled(vuart, true);

	aspeed_vuart_set_host_tx_discard(vuart, true);

	platform_set_drvdata(pdev, vuart);

	return 0;

err_clk_disable:

	clk_disable_unprepare(vuart->clk);

	irq_dispose_mapping(port.port.irq);

	return rc;

}

static int aspeed_vuart_remove(struct platform_device *pdev)

{

	struct aspeed_vuart *vuart = platform_get_drvdata(pdev);

	aspeed_vuart_set_enabled(vuart, false);

	serial8250_unregister_port(vuart->line);

	sysfs_remove_group(&vuart->dev->kobj, &aspeed_vuart_attr_group);

	clk_disable_unprepare(vuart->clk);

	return 0;

}

static const struct of_device_id aspeed_vuart_table[] = {

	{ .compatible = "aspeed,ast2400-vuart" },

	{ .compatible = "aspeed,ast2500-vuart" },

	{ },

};

static struct platform_driver aspeed_vuart_driver = {

	.driver = {

		.name = "aspeed-vuart",

		.of_match_table = aspeed_vuart_table,

	},

	.probe = aspeed_vuart_probe,

	.remove = aspeed_vuart_remove,

};

module_platform_driver(aspeed_vuart_driver);

MODULE_AUTHOR("Jeremy Kerr <jk@ozlabs.org>");

MODULE_LICENSE("GPL");

MODULE_DESCRIPTION("Driver for Aspeed VUART device");

	  To compile this driver as a module, choose M here: the module

	  will be called 8250_accent.

config SERIAL_8250_ASPEED_VUART

	tristate "Aspeed Virtual UART"

	depends on SERIAL_8250

	depends on OF

	help

	  If you want to use the virtual UART (VUART) device on Aspeed

	  BMC platforms, enable this option. This enables the 16550A-

	  compatible device on the local LPC bus, giving a UART device

	  with no physical RS232 connections.

config SERIAL_8250_BOCA

	tristate "Support Boca cards"

	depends on SERIAL_8250 != n && ISA && SERIAL_8250_MANY_PORTS

obj-$(CONFIG_SERIAL_8250_HP300)		+= 8250_hp300.o

obj-$(CONFIG_SERIAL_8250_CS)		+= serial_cs.o

obj-$(CONFIG_SERIAL_8250_ACORN)		+= 8250_acorn.o

obj-$(CONFIG_SERIAL_8250_ASPEED_VUART)	+= 8250_aspeed_vuart.o

obj-$(CONFIG_SERIAL_8250_BCM2835AUX)	+= 8250_bcm2835aux.o

obj-$(CONFIG_SERIAL_8250_CONSOLE)	+= 8250_early.o

obj-$(CONFIG_SERIAL_8250_FOURPORT)	+= 8250_fourport.o