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Haowei ZhengKexyBiscuit
Haowei Zheng
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KexyBiscuit
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FROMLIST: tty: serial: 8250: Add loongson uart driver support
Due to certain hardware design challenges, we have opted to utilize a dedicated UART driver to probe the UART interface. Signed-off-by: Haowei Zheng <[email protected]> Link: https://lore.kernel.org/all/[email protected]/ Signed-off-by: Kexy Biscuit <[email protected]> [Mingcong Bai: Resolved minor conflicts in MAINTAINERS, and drivers/tty/serial/8250/Kconfig.] Signed-off-by: Mingcong Bai <[email protected]>
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‎MAINTAINERS

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@@ -14155,6 +14155,13 @@ S: Maintained
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F: Documentation/devicetree/bindings/pwm/loongson,ls7a-pwm.yaml
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F: drivers/pwm/pwm-loongson.c
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LOONGSON UART DRIVER
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M: Haowei Zheng <[email protected]>
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L: [email protected]
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S: Maintained
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F: Documentation/devicetree/bindings/serial/loongson,uart.yaml
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F: drivers/tty/serial/8250/8250_loongson.c
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LOONGSON-2 SOC SERIES CLOCK DRIVER
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M: Yinbo Zhu <[email protected]>
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L: [email protected]

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

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// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* Copyright (C) 2020-2024 Loongson Technology Corporation Limited
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*/
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#include <linux/console.h>
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#include <linux/delay.h>
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#include <linux/io.h>
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#include <linux/module.h>
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#include <linux/reset.h>
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#include "8250.h"
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/* Flags */
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#define LOONGSON_UART_FRAC BIT(0)
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/* Quirks */
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#define LOONGSON_UART_QUIRK_MCR BIT(0)
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#define LOONGSON_UART_QUIRK_MSR BIT(1)
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struct loongson_uart_config {
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unsigned int flags;
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unsigned int quirks;
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};
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struct loongson_uart_data {
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struct reset_control *rst;
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int line;
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int mcr_invert;
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int msr_invert;
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const struct loongson_uart_config *config;
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};
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static const struct loongson_uart_config ls3a5000_uart_config = {
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.flags = 0,
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.quirks = LOONGSON_UART_QUIRK_MCR
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};
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static const struct loongson_uart_config ls7a_uart_config = {
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.flags = 0,
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.quirks = LOONGSON_UART_QUIRK_MCR | LOONGSON_UART_QUIRK_MSR
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};
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static const struct loongson_uart_config ls2k2000_uart_config = {
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.flags = LOONGSON_UART_FRAC,
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.quirks = LOONGSON_UART_QUIRK_MCR
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};
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static unsigned int serial_fixup(struct uart_port *p, unsigned int offset, unsigned int val)
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{
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struct loongson_uart_data *data = p->private_data;
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if (offset == UART_MCR)
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val ^= data->mcr_invert;
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if (offset == UART_MSR)
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val ^= data->msr_invert;
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return val;
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}
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static unsigned int loongson_serial_in(struct uart_port *p, int offset)
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{
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unsigned int val, offset0 = offset;
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offset = offset << p->regshift;
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val = readb(p->membase + offset);
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return serial_fixup(p, offset0, val);
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}
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static void loongson_serial_out(struct uart_port *p, int offset, int value)
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{
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offset = offset << p->regshift;
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writeb(serial_fixup(p, offset, value), p->membase + offset);
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}
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static unsigned int loongson_frac_get_divisor(struct uart_port *port,
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unsigned int baud,
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unsigned int *frac)
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{
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unsigned int quot;
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quot = DIV_ROUND_CLOSEST((port->uartclk << 4), baud);
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*frac = quot & 0xff;
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return quot >> 8;
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}
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static void loongson_frac_set_divisor(struct uart_port *port, unsigned int baud,
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unsigned int quot, unsigned int quot_frac)
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{
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struct uart_8250_port *up = up_to_u8250p(port);
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serial_port_out(port, UART_LCR, up->lcr | UART_LCR_DLAB);
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serial_dl_write(up, quot);
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serial_port_out(port, 0x2, quot_frac);
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}
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static int loongson_uart_probe(struct platform_device *pdev)
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{
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struct uart_8250_port uart = {};
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struct loongson_uart_data *data;
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struct uart_port *port;
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struct resource *res;
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int ret;
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port = &uart.port;
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spin_lock_init(&port->lock);
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res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
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if (!res)
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return -ENODEV;
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port->flags = UPF_SHARE_IRQ | UPF_FIXED_PORT | UPF_FIXED_TYPE | UPF_IOREMAP;
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port->iotype = UPIO_MEM;
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port->regshift = 0;
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port->dev = &pdev->dev;
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port->type = PORT_LOONGSON;
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port->mapbase = res->start;
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port->mapsize = resource_size(res);
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port->serial_in = loongson_serial_in;
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port->serial_out = loongson_serial_out;
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port->irq = platform_get_irq(pdev, 0);
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if (port->irq < 0)
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return -EINVAL;
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data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
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if (!data)
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return -ENOMEM;
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data->config = device_get_match_data(&pdev->dev);
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port->private_data = data;
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if (data->config->flags & LOONGSON_UART_FRAC) {
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port->get_divisor = loongson_frac_get_divisor;
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port->set_divisor = loongson_frac_set_divisor;
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}
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if (data->config->quirks & LOONGSON_UART_QUIRK_MCR)
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data->mcr_invert |= (UART_MCR_RTS | UART_MCR_DTR);
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if (data->config->quirks & LOONGSON_UART_QUIRK_MSR)
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data->msr_invert |= (UART_MSR_CTS | UART_MSR_DSR);
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data->rst = devm_reset_control_get_optional_shared(&pdev->dev, NULL);
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if (IS_ERR(data->rst))
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return PTR_ERR(data->rst);
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device_property_read_u32(&pdev->dev, "clock-frequency", &port->uartclk);
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ret = reset_control_deassert(data->rst);
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if (ret)
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goto err_unprepare;
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ret = serial8250_register_8250_port(&uart);
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if (ret < 0)
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goto err_unprepare;
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platform_set_drvdata(pdev, data);
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data->line = ret;
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return 0;
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err_unprepare:
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reset_control_assert(data->rst);
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return ret;
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}
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static void loongson_uart_remove(struct platform_device *pdev)
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{
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struct loongson_uart_data *data = platform_get_drvdata(pdev);
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serial8250_unregister_port(data->line);
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reset_control_assert(data->rst);
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}
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#ifdef CONFIG_PM_SLEEP
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static int loongson_uart_suspend(struct device *dev)
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{
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struct loongson_uart_data *data = dev_get_drvdata(dev);
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serial8250_suspend_port(data->line);
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return 0;
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}
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static int loongson_uart_resume(struct device *dev)
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{
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struct loongson_uart_data *data = dev_get_drvdata(dev);
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serial8250_resume_port(data->line);
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return 0;
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}
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#endif
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static const struct dev_pm_ops loongson_uart_pm_ops = {
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SET_SYSTEM_SLEEP_PM_OPS(loongson_uart_suspend, loongson_uart_resume)
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};
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static const struct of_device_id of_platform_serial_table[] = {
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{.compatible = "loongson,ls7a-uart", .data = &ls7a_uart_config},
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{.compatible = "loongson,ls3a5000-uart", .data = &ls3a5000_uart_config},
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{.compatible = "loongson,ls2k2000-uart", .data = &ls2k2000_uart_config},
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{},
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};
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MODULE_DEVICE_TABLE(of, of_platform_serial_table);
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static struct platform_driver loongson_uart_driver = {
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.probe = loongson_uart_probe,
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.remove = loongson_uart_remove,
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.driver = {
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.name = "loongson-uart",
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.pm = &loongson_uart_pm_ops,
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.of_match_table = of_platform_serial_table,
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},
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};
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module_platform_driver(loongson_uart_driver);
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MODULE_DESCRIPTION("LOONGSON 8250 Driver");
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MODULE_AUTHOR("Haowei Zheng <[email protected]>");
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MODULE_LICENSE("GPL");

‎drivers/tty/serial/8250/8250_port.c

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@@ -319,6 +319,14 @@ static const struct serial8250_config uart_config[] = {
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.rxtrig_bytes = {1, 8, 16, 30},
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.flags = UART_CAP_FIFO | UART_CAP_AFE,
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},
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[PORT_LOONGSON] = {
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.name = "Loongson",
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.fifo_size = 16,
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.tx_loadsz = 16,
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.fcr = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10,
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.rxtrig_bytes = {1, 4, 8, 14},
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.flags = UART_CAP_FIFO,
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},
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};
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/* Uart divisor latch read */

‎drivers/tty/serial/8250/Kconfig

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@@ -569,6 +569,15 @@ config SERIAL_8250_BCM7271
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including DMA support and high accuracy BAUD rates, say
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Y to this option. If unsure, say N.
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config SERIAL_8250_LOONGSON
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tristate "Loongson 8250 serial port support"
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default SERIAL_8250
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depends on SERIAL_8250
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depends on LOONGARCH
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help
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If you have machine with Loongson and want to use this serial driver,
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say Y to this option. If unsure, say N.
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config SERIAL_8250_NI
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tristate "NI 16550 based serial port"
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depends on SERIAL_8250

‎drivers/tty/serial/8250/Makefile

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@@ -52,5 +52,6 @@ obj-$(CONFIG_SERIAL_8250_RT288X) += 8250_rt288x.o
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obj-$(CONFIG_SERIAL_8250_CS) += serial_cs.o
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obj-$(CONFIG_SERIAL_8250_UNIPHIER) += 8250_uniphier.o
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obj-$(CONFIG_SERIAL_8250_TEGRA) += 8250_tegra.o
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obj-$(CONFIG_SERIAL_8250_LOONGSON) += 8250_loongson.o
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CFLAGS_8250_ingenic.o += -I$(srctree)/scripts/dtc/libfdt

‎include/uapi/linux/serial_core.h

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#define PORT_ALTR_16550_F128 28 /* Altera 16550 UART with 128 FIFOs */
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#define PORT_RT2880 29 /* Ralink RT2880 internal UART */
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#define PORT_16550A_FSL64 30 /* Freescale 16550 UART with 64 FIFOs */
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#define PORT_LOONGSON 31 /* Loongson 16550 UART*/
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/*
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* ARM specific type numbers. These are not currently guaranteed

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