8250_loongson.c

  1// SPDX-License-Identifier: GPL-2.0-or-later
  2/*
  3 * Serial Port driver for Loongson family chips
  4 *
  5 * Copyright (C) 2020-2025 Loongson Technology Corporation Limited
  6 */
  7
  8#include <linux/bitfield.h>
  9#include <linux/bits.h>
 10#include <linux/clk.h>
 11#include <linux/console.h>
 12#include <linux/module.h>
 13#include <linux/io.h>
 14#include <linux/property.h>
 15#include <linux/math.h>
 16#include <linux/mod_devicetable.h>
 17#include <linux/pm.h>
 18#include <linux/reset.h>
 19
 20#include "8250.h"
 21
 22/* Divisor Latch Fraction Register */
 23#define LOONGSON_UART_DLF		0x2
 24
 25#define LOONGSON_QUOT_FRAC_MASK		GENMASK(7, 0)
 26#define LOONGSON_QUOT_DIV_MASK		GENMASK(15, 8)
 27
 28struct loongson_uart_ddata {
 29	bool has_frac;
 30	u8 mcr_invert;
 31	u8 msr_invert;
 32};
 33
 34static const struct loongson_uart_ddata ls2k0500_uart_data = {
 35	.has_frac = false,
 36	.mcr_invert = UART_MCR_RTS | UART_MCR_DTR,
 37	.msr_invert = UART_MSR_CTS | UART_MSR_DSR,
 38};
 39
 40static const struct loongson_uart_ddata ls2k1500_uart_data = {
 41	.has_frac = true,
 42	.mcr_invert = UART_MCR_RTS | UART_MCR_DTR,
 43	.msr_invert = 0,
 44};
 45
 46struct loongson_uart_priv {
 47	int line;
 48	struct clk *clk;
 49	struct resource *res;
 50	struct reset_control *rst;
 51	const struct loongson_uart_ddata *ddata;
 52};
 53
 54static u8 serial_fixup(struct uart_port *p, unsigned int offset, u8 val)
 55{
 56	struct loongson_uart_priv *priv = p->private_data;
 57
 58	switch (offset) {
 59	case UART_MCR:
 60		return val ^ priv->ddata->mcr_invert;
 61	case UART_MSR:
 62		return val ^ priv->ddata->msr_invert;
 63	default:
 64		return val;
 65	}
 66}
 67
 68static u32 loongson_serial_in(struct uart_port *p, unsigned int offset)
 69{
 70	u8 val;
 71
 72	val = readb(p->membase + (offset << p->regshift));
 73
 74	return serial_fixup(p, offset, val);
 75}
 76
 77static void loongson_serial_out(struct uart_port *p, unsigned int offset, unsigned int value)
 78{
 79	u8 val;
 80
 81	offset <<= p->regshift;
 82	val = serial_fixup(p, offset, value);
 83	writeb(val, p->membase + offset);
 84}
 85
 86static unsigned int loongson_frac_get_divisor(struct uart_port *port, unsigned int baud,
 87					      unsigned int *frac)
 88{
 89	unsigned int quot;
 90
 91	quot = DIV_ROUND_CLOSEST((port->uartclk << 4), baud);
 92	*frac = FIELD_GET(LOONGSON_QUOT_FRAC_MASK, quot);
 93
 94	return FIELD_GET(LOONGSON_QUOT_DIV_MASK, quot);
 95}
 96
 97static void loongson_frac_set_divisor(struct uart_port *port, unsigned int baud,
 98				      unsigned int quot, unsigned int quot_frac)
 99{
100	struct uart_8250_port *up = up_to_u8250p(port);
101
102	serial_port_out(port, UART_LCR, up->lcr | UART_LCR_DLAB);
103	serial_dl_write(up, quot);
104	serial_port_out(port, LOONGSON_UART_DLF, quot_frac);
105}
106
107static int loongson_uart_probe(struct platform_device *pdev)
108{
109	struct device *dev = &pdev->dev;
110	struct uart_8250_port uart = {};
111	struct loongson_uart_priv *priv;
112	struct uart_port *port;
113	int ret;
114
115	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
116	if (!priv)
117		return -ENOMEM;
118
119	priv->ddata = device_get_match_data(dev);
120
121	port = &uart.port;
122	spin_lock_init(&port->lock);
123	port->flags = UPF_SHARE_IRQ | UPF_FIXED_PORT | UPF_FIXED_TYPE | UPF_IOREMAP;
124	port->iotype = UPIO_MEM;
125	port->regshift = 0;
126	port->dev = dev;
127	port->type = PORT_16550A;
128	port->private_data = priv;
129
130	port->membase = devm_platform_get_and_ioremap_resource(pdev, 0, &priv->res);
131	if (IS_ERR(port->membase))
132		return PTR_ERR(port->membase);
133
134	port->mapbase = priv->res->start;
135	port->mapsize = resource_size(priv->res);
136	port->serial_in = loongson_serial_in;
137	port->serial_out = loongson_serial_out;
138
139	if (priv->ddata->has_frac) {
140		port->get_divisor = loongson_frac_get_divisor;
141		port->set_divisor = loongson_frac_set_divisor;
142	}
143
144	ret = uart_read_port_properties(port);
145	if (ret)
146		return ret;
147
148	if (!port->uartclk) {
149		priv->clk = devm_clk_get_enabled(dev, NULL);
150		if (IS_ERR(priv->clk))
151			return dev_err_probe(dev, PTR_ERR(priv->clk),
152					     "Unable to determine clock frequency!\n");
153		port->uartclk = clk_get_rate(priv->clk);
154	}
155
156	priv->rst = devm_reset_control_get_optional_shared(dev, NULL);
157	if (IS_ERR(priv->rst))
158		return PTR_ERR(priv->rst);
159
160	ret = reset_control_deassert(priv->rst);
161	if (ret)
162		return ret;
163
164	ret = serial8250_register_8250_port(&uart);
165	if (ret < 0) {
166		reset_control_assert(priv->rst);
167		return ret;
168	}
169
170	priv->line = ret;
171	platform_set_drvdata(pdev, priv);
172
173	return 0;
174}
175
176static void loongson_uart_remove(struct platform_device *pdev)
177{
178	struct loongson_uart_priv *priv = platform_get_drvdata(pdev);
179
180	serial8250_unregister_port(priv->line);
181	reset_control_assert(priv->rst);
182}
183
184static int loongson_uart_suspend(struct device *dev)
185{
186	struct loongson_uart_priv *priv = dev_get_drvdata(dev);
187	struct uart_8250_port *up = serial8250_get_port(priv->line);
188
189	serial8250_suspend_port(priv->line);
190
191	if (!uart_console(&up->port) || console_suspend_enabled)
192		clk_disable_unprepare(priv->clk);
193
194	return 0;
195}
196
197static int loongson_uart_resume(struct device *dev)
198{
199	struct loongson_uart_priv *priv = dev_get_drvdata(dev);
200	struct uart_8250_port *up = serial8250_get_port(priv->line);
201	int ret;
202
203	if (!uart_console(&up->port) || console_suspend_enabled) {
204		ret = clk_prepare_enable(priv->clk);
205		if (ret)
206			return ret;
207	}
208
209	serial8250_resume_port(priv->line);
210
211	return 0;
212}
213
214static DEFINE_SIMPLE_DEV_PM_OPS(loongson_uart_pm_ops, loongson_uart_suspend,
215				loongson_uart_resume);
216
217static const struct of_device_id loongson_uart_of_ids[] = {
218	{ .compatible = "loongson,ls2k0500-uart", .data = &ls2k0500_uart_data },
219	{ .compatible = "loongson,ls2k1500-uart", .data = &ls2k1500_uart_data },
220	{ },
221};
222MODULE_DEVICE_TABLE(of, loongson_uart_of_ids);
223
224static struct platform_driver loongson_uart_driver = {
225	.probe = loongson_uart_probe,
226	.remove = loongson_uart_remove,
227	.driver = {
228		.name = "loongson-uart",
229		.pm = pm_ptr(&loongson_uart_pm_ops),
230		.of_match_table = loongson_uart_of_ids,
231	},
232};
233
234module_platform_driver(loongson_uart_driver);
235
236MODULE_DESCRIPTION("Loongson UART driver");
237MODULE_AUTHOR("Loongson Technology Corporation Limited.");
238MODULE_LICENSE("GPL");