// SPDX-License-Identifier: GPL-2.0 /* * Serial port driver for BCM2835AUX UART * * Copyright (C) 2016 Martin Sperl * * Based on 8250_lpc18xx.c: * Copyright (C) 2015 Joachim Eastwood * * The bcm2835aux is capable of RTS auto flow-control, but this driver doesn't * take advantage of it yet. When adding support, be sure not to enable it * simultaneously to rs485. */ #include #include #include #include #include #include #include "8250.h" #define BCM2835_AUX_UART_CNTL 8 #define BCM2835_AUX_UART_CNTL_RXEN 0x01 /* Receiver enable */ #define BCM2835_AUX_UART_CNTL_TXEN 0x02 /* Transmitter enable */ #define BCM2835_AUX_UART_CNTL_AUTORTS 0x04 /* RTS set by RX fill level */ #define BCM2835_AUX_UART_CNTL_AUTOCTS 0x08 /* CTS stops transmitter */ #define BCM2835_AUX_UART_CNTL_RTS3 0x00 /* RTS set until 3 chars left */ #define BCM2835_AUX_UART_CNTL_RTS2 0x10 /* RTS set until 2 chars left */ #define BCM2835_AUX_UART_CNTL_RTS1 0x20 /* RTS set until 1 chars left */ #define BCM2835_AUX_UART_CNTL_RTS4 0x30 /* RTS set until 4 chars left */ #define BCM2835_AUX_UART_CNTL_RTSINV 0x40 /* Invert auto RTS polarity */ #define BCM2835_AUX_UART_CNTL_CTSINV 0x80 /* Invert auto CTS polarity */ /** * struct bcm2835aux_data - driver private data of BCM2835 auxiliary UART * @clk: clock producer of the port's uartclk * @line: index of the port's serial8250_ports[] entry * @cntl: cached copy of CNTL register */ struct bcm2835aux_data { struct clk *clk; int line; u32 cntl; }; struct bcm2835_aux_serial_driver_data { resource_size_t offset; }; static void bcm2835aux_rs485_start_tx(struct uart_8250_port *up) { if (!(up->port.rs485.flags & SER_RS485_RX_DURING_TX)) { struct bcm2835aux_data *data = dev_get_drvdata(up->port.dev); data->cntl &= ~BCM2835_AUX_UART_CNTL_RXEN; serial_out(up, BCM2835_AUX_UART_CNTL, data->cntl); } /* * On the bcm2835aux, the MCR register contains no other * flags besides RTS. So no need for a read-modify-write. */ if (up->port.rs485.flags & SER_RS485_RTS_ON_SEND) serial8250_out_MCR(up, 0); else serial8250_out_MCR(up, UART_MCR_RTS); } static void bcm2835aux_rs485_stop_tx(struct uart_8250_port *up) { if (up->port.rs485.flags & SER_RS485_RTS_AFTER_SEND) serial8250_out_MCR(up, 0); else serial8250_out_MCR(up, UART_MCR_RTS); if (!(up->port.rs485.flags & SER_RS485_RX_DURING_TX)) { struct bcm2835aux_data *data = dev_get_drvdata(up->port.dev); data->cntl |= BCM2835_AUX_UART_CNTL_RXEN; serial_out(up, BCM2835_AUX_UART_CNTL, data->cntl); } } static int bcm2835aux_serial_probe(struct platform_device *pdev) { const struct bcm2835_aux_serial_driver_data *bcm_data; struct uart_8250_port up = { }; struct bcm2835aux_data *data; resource_size_t offset = 0; struct resource *res; unsigned int uartclk; int ret; /* allocate the custom structure */ data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL); if (!data) return -ENOMEM; /* initialize data */ up.capabilities = UART_CAP_FIFO | UART_CAP_MINI; up.port.dev = &pdev->dev; up.port.regshift = 2; up.port.type = PORT_16550; up.port.iotype = UPIO_MEM; up.port.fifosize = 8; up.port.flags = UPF_SHARE_IRQ | UPF_FIXED_PORT | UPF_FIXED_TYPE | UPF_SKIP_TEST | UPF_IOREMAP; up.port.rs485_config = serial8250_em485_config; up.port.rs485_supported = serial8250_em485_supported; up.rs485_start_tx = bcm2835aux_rs485_start_tx; up.rs485_stop_tx = bcm2835aux_rs485_stop_tx; /* initialize cached copy with power-on reset value */ data->cntl = BCM2835_AUX_UART_CNTL_RXEN | BCM2835_AUX_UART_CNTL_TXEN; platform_set_drvdata(pdev, data); /* get the clock - this also enables the HW */ data->clk = devm_clk_get_optional(&pdev->dev, NULL); /* get the interrupt */ ret = platform_get_irq(pdev, 0); if (ret < 0) return ret; up.port.irq = ret; /* map the main registers */ res = platform_get_resource(pdev, IORESOURCE_MEM, 0); if (!res) { dev_err(&pdev->dev, "memory resource not found"); return -EINVAL; } bcm_data = device_get_match_data(&pdev->dev); /* Some UEFI implementations (e.g. tianocore/edk2 for the Raspberry Pi) * describe the miniuart with a base address that encompasses the auxiliary * registers shared between the miniuart and spi. * * This is due to historical reasons, see discussion here : * https://edk2.groups.io/g/devel/topic/87501357#84349 * * We need to add the offset between the miniuart and auxiliary * registers to get the real miniuart base address. */ if (bcm_data) offset = bcm_data->offset; up.port.mapbase = res->start + offset; up.port.mapsize = resource_size(res) - offset; /* Check for a fixed line number */ ret = of_alias_get_id(pdev->dev.of_node, "serial"); if (ret >= 0) up.port.line = ret; /* enable the clock as a last step */ ret = clk_prepare_enable(data->clk); if (ret) { dev_err(&pdev->dev, "unable to enable uart clock - %d\n", ret); return ret; } uartclk = clk_get_rate(data->clk); if (!uartclk) { ret = device_property_read_u32(&pdev->dev, "clock-frequency", &uartclk); if (ret) { dev_err_probe(&pdev->dev, ret, "could not get clk rate\n"); goto dis_clk; } } /* the HW-clock divider for bcm2835aux is 8, * but 8250 expects a divider of 16, * so we have to multiply the actual clock by 2 * to get identical baudrates. */ up.port.uartclk = uartclk * 2; /* register the port */ ret = serial8250_register_8250_port(&up); if (ret < 0) { dev_err_probe(&pdev->dev, ret, "unable to register 8250 port\n"); goto dis_clk; } data->line = ret; return 0; dis_clk: clk_disable_unprepare(data->clk); return ret; } static void bcm2835aux_serial_remove(struct platform_device *pdev) { struct bcm2835aux_data *data = platform_get_drvdata(pdev); serial8250_unregister_port(data->line); clk_disable_unprepare(data->clk); } static const struct bcm2835_aux_serial_driver_data bcm2835_acpi_data = { .offset = 0x40, }; static const struct of_device_id bcm2835aux_serial_match[] = { { .compatible = "brcm,bcm2835-aux-uart" }, { }, }; MODULE_DEVICE_TABLE(of, bcm2835aux_serial_match); static const struct acpi_device_id bcm2835aux_serial_acpi_match[] = { { "BCM2836", (kernel_ulong_t)&bcm2835_acpi_data }, { } }; MODULE_DEVICE_TABLE(acpi, bcm2835aux_serial_acpi_match); static struct platform_driver bcm2835aux_serial_driver = { .driver = { .name = "bcm2835-aux-uart", .of_match_table = bcm2835aux_serial_match, .acpi_match_table = bcm2835aux_serial_acpi_match, }, .probe = bcm2835aux_serial_probe, .remove_new = bcm2835aux_serial_remove, }; module_platform_driver(bcm2835aux_serial_driver); #ifdef CONFIG_SERIAL_8250_CONSOLE static int __init early_bcm2835aux_setup(struct earlycon_device *device, const char *options) { if (!device->port.membase) return -ENODEV; device->port.iotype = UPIO_MEM32; device->port.regshift = 2; return early_serial8250_setup(device, NULL); } OF_EARLYCON_DECLARE(bcm2835aux, "brcm,bcm2835-aux-uart", early_bcm2835aux_setup); #endif MODULE_DESCRIPTION("BCM2835 auxiliar UART driver"); MODULE_AUTHOR("Martin Sperl "); MODULE_LICENSE("GPL v2");