Commit 25e95d76 authored by Binbin Zhou's avatar Binbin Zhou Committed by Greg Kroah-Hartman
Browse files

serial: 8250: Add Loongson uart driver support 



Add the driver for on-chip UART used on Loongson family chips.

The hardware is similar to NS16550A, but there are the following
differences:
 - Some chips (such as Loongson-2K2000) have added a fractional division
   register to obtain the required baud rate accurately, so the
   {get,set}_divisor callback is overridden.
 - Due to hardware defects, quirk handling is required for
   UART_MCR/UART_MSR.

Co-developed-by: default avatarHaowei Zheng <zhenghaowei@loongson.cn>
Signed-off-by: default avatarHaowei Zheng <zhenghaowei@loongson.cn>
Signed-off-by: default avatarBinbin Zhou <zhoubinbin@loongson.cn>
Reviewed-by: default avatarHuacai Chen <chenhuacai@loongson.cn>
Link: https://patch.msgid.link/2c2a01a276b9250efea0c7aa190efecdfd6fdf5a.1760166651.git.zhoubinbin@loongson.cn


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 7cf86b66

drivers/tty/serial/8250/8250_loongson.c

0 → 100644
+238 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0-or-later

/*

 * Serial Port driver for Loongson family chips

 *

 * Copyright (C) 2020-2025 Loongson Technology Corporation Limited

 */



#include <linux/bitfield.h>

#include <linux/bits.h>

#include <linux/clk.h>

#include <linux/console.h>

#include <linux/module.h>

#include <linux/io.h>

#include <linux/property.h>

#include <linux/math.h>

#include <linux/mod_devicetable.h>

#include <linux/pm.h>

#include <linux/reset.h>



#include "8250.h"



/* Divisor Latch Fraction Register */

#define LOONGSON_UART_DLF		0x2



#define LOONGSON_QUOT_FRAC_MASK		GENMASK(7, 0)

#define LOONGSON_QUOT_DIV_MASK		GENMASK(15, 8)



struct loongson_uart_ddata {

	bool has_frac;

	u8 mcr_invert;

	u8 msr_invert;

};



static const struct loongson_uart_ddata ls2k0500_uart_data = {

	.has_frac = false,

	.mcr_invert = UART_MCR_RTS | UART_MCR_DTR,

	.msr_invert = UART_MSR_CTS | UART_MSR_DSR,

};



static const struct loongson_uart_ddata ls2k1500_uart_data = {

	.has_frac = true,

	.mcr_invert = UART_MCR_RTS | UART_MCR_DTR,

	.msr_invert = 0,

};



struct loongson_uart_priv {

	int line;

	struct clk *clk;

	struct resource *res;

	struct reset_control *rst;

	const struct loongson_uart_ddata *ddata;

};



static u8 serial_fixup(struct uart_port *p, unsigned int offset, u8 val)

{

	struct loongson_uart_priv *priv = p->private_data;



	switch (offset) {

	case UART_MCR:

		return val ^ priv->ddata->mcr_invert;

	case UART_MSR:

		return val ^ priv->ddata->msr_invert;

	default:

		return val;

	}

}



static u32 loongson_serial_in(struct uart_port *p, unsigned int offset)

{

	u8 val;



	val = readb(p->membase + (offset << p->regshift));



	return serial_fixup(p, offset, val);

}



static void loongson_serial_out(struct uart_port *p, unsigned int offset, unsigned int value)

{

	u8 val;



	offset <<= p->regshift;

	val = serial_fixup(p, offset, value);

	writeb(val, p->membase + offset);

}



static unsigned int loongson_frac_get_divisor(struct uart_port *port, unsigned int baud,

					      unsigned int *frac)

{

	unsigned int quot;



	quot = DIV_ROUND_CLOSEST((port->uartclk << 4), baud);

	*frac = FIELD_GET(LOONGSON_QUOT_FRAC_MASK, quot);



	return FIELD_GET(LOONGSON_QUOT_DIV_MASK, quot);

}



static void loongson_frac_set_divisor(struct uart_port *port, unsigned int baud,

				      unsigned int quot, unsigned int quot_frac)

{

	struct uart_8250_port *up = up_to_u8250p(port);



	serial_port_out(port, UART_LCR, up->lcr | UART_LCR_DLAB);

	serial_dl_write(up, quot);

	serial_port_out(port, LOONGSON_UART_DLF, quot_frac);

}



static int loongson_uart_probe(struct platform_device *pdev)

{

	struct device *dev = &pdev->dev;

	struct uart_8250_port uart = {};

	struct loongson_uart_priv *priv;

	struct uart_port *port;

	int ret;



	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);

	if (!priv)

		return -ENOMEM;



	priv->ddata = device_get_match_data(dev);



	port = &uart.port;

	spin_lock_init(&port->lock);

	port->flags = UPF_SHARE_IRQ | UPF_FIXED_PORT | UPF_FIXED_TYPE | UPF_IOREMAP;

	port->iotype = UPIO_MEM;

	port->regshift = 0;

	port->dev = dev;

	port->type = PORT_16550A;

	port->private_data = priv;



	port->membase = devm_platform_get_and_ioremap_resource(pdev, 0, &priv->res);

	if (!port->membase)

		return -ENOMEM;



	port->mapbase = priv->res->start;

	port->mapsize = resource_size(priv->res);

	port->serial_in = loongson_serial_in;

	port->serial_out = loongson_serial_out;



	if (priv->ddata->has_frac) {

		port->get_divisor = loongson_frac_get_divisor;

		port->set_divisor = loongson_frac_set_divisor;

	}



	ret = uart_read_port_properties(port);

	if (ret)

		return ret;



	if (!port->uartclk) {

		priv->clk = devm_clk_get_enabled(dev, NULL);

		if (IS_ERR(priv->clk))

			return dev_err_probe(dev, PTR_ERR(priv->clk),

					     "Unable to determine clock frequency!\n");

		port->uartclk = clk_get_rate(priv->clk);

	}



	priv->rst = devm_reset_control_get_optional_shared(dev, NULL);

	if (IS_ERR(priv->rst))

		return PTR_ERR(priv->rst);



	ret = reset_control_deassert(priv->rst);

	if (ret)

		return ret;



	ret = serial8250_register_8250_port(&uart);

	if (ret < 0) {

		reset_control_assert(priv->rst);

		return ret;

	}



	priv->line = ret;

	platform_set_drvdata(pdev, priv);



	return 0;

}



static void loongson_uart_remove(struct platform_device *pdev)

{

	struct loongson_uart_priv *priv = platform_get_drvdata(pdev);



	serial8250_unregister_port(priv->line);

	reset_control_assert(priv->rst);

}



static int loongson_uart_suspend(struct device *dev)

{

	struct loongson_uart_priv *priv = dev_get_drvdata(dev);

	struct uart_8250_port *up = serial8250_get_port(priv->line);



	serial8250_suspend_port(priv->line);



	if (!uart_console(&up->port) || console_suspend_enabled)

		clk_disable_unprepare(priv->clk);



	return 0;

}



static int loongson_uart_resume(struct device *dev)

{

	struct loongson_uart_priv *priv = dev_get_drvdata(dev);

	struct uart_8250_port *up = serial8250_get_port(priv->line);

	int ret;



	if (!uart_console(&up->port) || console_suspend_enabled) {

		ret = clk_prepare_enable(priv->clk);

		if (ret)

			return ret;

	}



	serial8250_resume_port(priv->line);



	return 0;

}



static DEFINE_SIMPLE_DEV_PM_OPS(loongson_uart_pm_ops, loongson_uart_suspend,

				loongson_uart_resume);



static const struct of_device_id loongson_uart_of_ids[] = {

	{ .compatible = "loongson,ls2k0500-uart", .data = &ls2k0500_uart_data },

	{ .compatible = "loongson,ls2k1500-uart", .data = &ls2k1500_uart_data },

	{ },

};

MODULE_DEVICE_TABLE(of, loongson_uart_of_ids);



static struct platform_driver loongson_uart_driver = {

	.probe = loongson_uart_probe,

	.remove = loongson_uart_remove,

	.driver = {

		.name = "loongson-uart",

		.pm = pm_ptr(&loongson_uart_pm_ops),

		.of_match_table = loongson_uart_of_ids,

	},

};



module_platform_driver(loongson_uart_driver);



MODULE_DESCRIPTION("Loongson UART driver");

MODULE_AUTHOR("Loongson Technology Corporation Limited.");

MODULE_LICENSE("GPL");

drivers/tty/serial/8250/Kconfig

+10 −0
Original line number Diff line number Diff line
@@ -464,6 +464,16 @@ config SERIAL_8250_OMAP_TTYO_FIXUP 
	  not booting kernel because the serial console remains silent in case

	  they forgot to update the command line.



config SERIAL_8250_LOONGSON

	tristate "Loongson 8250 based serial port"

	depends on SERIAL_8250

	depends on LOONGARCH || COMPILE_TEST

	help

	  If you have a machine based on LoongArch CPU you can enable

	  its onboard serial ports by enabling this option. The option

	  is applicable to both devicetree and ACPI, say Y to this option.

	  If unsure, say N.



config SERIAL_8250_LPC18XX

	tristate "NXP LPC18xx/43xx serial port support"

	depends on SERIAL_8250 && OF && (ARCH_LPC18XX || COMPILE_TEST)

drivers/tty/serial/8250/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -39,6 +39,7 @@ obj-$(CONFIG_SERIAL_8250_HUB6) += 8250_hub6.o 
obj-$(CONFIG_SERIAL_8250_INGENIC)	+= 8250_ingenic.o

obj-$(CONFIG_SERIAL_8250_IOC3)		+= 8250_ioc3.o

obj-$(CONFIG_SERIAL_8250_KEBA)		+= 8250_keba.o

obj-$(CONFIG_SERIAL_8250_LOONGSON)	+= 8250_loongson.o

obj-$(CONFIG_SERIAL_8250_LPC18XX)	+= 8250_lpc18xx.o

obj-$(CONFIG_SERIAL_8250_LPSS)		+= 8250_lpss.o

obj-$(CONFIG_SERIAL_8250_MEN_MCB)	+= 8250_men_mcb.o