1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Serial port driver for BCM2835AUX UART 4 * 5 * Copyright (C) 2016 Martin Sperl <kernel@martin.sperl.org> 6 * 7 * Based on 8250_lpc18xx.c: 8 * Copyright (C) 2015 Joachim Eastwood <manabian@gmail.com> 9 * 10 * The bcm2835aux is capable of RTS auto flow-control, but this driver doesn't 11 * take advantage of it yet. When adding support, be sure not to enable it 12 * simultaneously to rs485. 13 */ 14 15 #include <linux/clk.h> 16 #include <linux/io.h> 17 #include <linux/module.h> 18 #include <linux/of.h> 19 #include <linux/platform_device.h> 20 #include <linux/property.h> 21 22 #include "8250.h" 23 24 #define BCM2835_AUX_UART_CNTL 8 25 #define BCM2835_AUX_UART_CNTL_RXEN 0x01 /* Receiver enable */ 26 #define BCM2835_AUX_UART_CNTL_TXEN 0x02 /* Transmitter enable */ 27 #define BCM2835_AUX_UART_CNTL_AUTORTS 0x04 /* RTS set by RX fill level */ 28 #define BCM2835_AUX_UART_CNTL_AUTOCTS 0x08 /* CTS stops transmitter */ 29 #define BCM2835_AUX_UART_CNTL_RTS3 0x00 /* RTS set until 3 chars left */ 30 #define BCM2835_AUX_UART_CNTL_RTS2 0x10 /* RTS set until 2 chars left */ 31 #define BCM2835_AUX_UART_CNTL_RTS1 0x20 /* RTS set until 1 chars left */ 32 #define BCM2835_AUX_UART_CNTL_RTS4 0x30 /* RTS set until 4 chars left */ 33 #define BCM2835_AUX_UART_CNTL_RTSINV 0x40 /* Invert auto RTS polarity */ 34 #define BCM2835_AUX_UART_CNTL_CTSINV 0x80 /* Invert auto CTS polarity */ 35 36 /** 37 * struct bcm2835aux_data - driver private data of BCM2835 auxiliary UART 38 * @clk: clock producer of the port's uartclk 39 * @line: index of the port's serial8250_ports[] entry 40 * @cntl: cached copy of CNTL register 41 */ 42 struct bcm2835aux_data { 43 struct clk *clk; 44 int line; 45 u32 cntl; 46 }; 47 48 struct bcm2835_aux_serial_driver_data { 49 resource_size_t offset; 50 }; 51 52 static void bcm2835aux_rs485_start_tx(struct uart_8250_port *up) 53 { 54 if (!(up->port.rs485.flags & SER_RS485_RX_DURING_TX)) { 55 struct bcm2835aux_data *data = dev_get_drvdata(up->port.dev); 56 57 data->cntl &= ~BCM2835_AUX_UART_CNTL_RXEN; 58 serial_out(up, BCM2835_AUX_UART_CNTL, data->cntl); 59 } 60 61 /* 62 * On the bcm2835aux, the MCR register contains no other 63 * flags besides RTS. So no need for a read-modify-write. 64 */ 65 if (up->port.rs485.flags & SER_RS485_RTS_ON_SEND) 66 serial8250_out_MCR(up, 0); 67 else 68 serial8250_out_MCR(up, UART_MCR_RTS); 69 } 70 71 static void bcm2835aux_rs485_stop_tx(struct uart_8250_port *up) 72 { 73 if (up->port.rs485.flags & SER_RS485_RTS_AFTER_SEND) 74 serial8250_out_MCR(up, 0); 75 else 76 serial8250_out_MCR(up, UART_MCR_RTS); 77 78 if (!(up->port.rs485.flags & SER_RS485_RX_DURING_TX)) { 79 struct bcm2835aux_data *data = dev_get_drvdata(up->port.dev); 80 81 data->cntl |= BCM2835_AUX_UART_CNTL_RXEN; 82 serial_out(up, BCM2835_AUX_UART_CNTL, data->cntl); 83 } 84 } 85 86 static int bcm2835aux_serial_probe(struct platform_device *pdev) 87 { 88 const struct bcm2835_aux_serial_driver_data *bcm_data; 89 struct uart_8250_port up = { }; 90 struct bcm2835aux_data *data; 91 resource_size_t offset = 0; 92 struct resource *res; 93 unsigned int uartclk; 94 int ret; 95 96 /* allocate the custom structure */ 97 data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL); 98 if (!data) 99 return -ENOMEM; 100 101 /* initialize data */ 102 up.capabilities = UART_CAP_FIFO | UART_CAP_MINI; 103 up.port.dev = &pdev->dev; 104 up.port.regshift = 2; 105 up.port.type = PORT_16550; 106 up.port.iotype = UPIO_MEM; 107 up.port.fifosize = 8; 108 up.port.flags = UPF_SHARE_IRQ | UPF_FIXED_PORT | UPF_FIXED_TYPE | 109 UPF_SKIP_TEST | UPF_IOREMAP; 110 up.port.rs485_config = serial8250_em485_config; 111 up.port.rs485_supported = serial8250_em485_supported; 112 up.rs485_start_tx = bcm2835aux_rs485_start_tx; 113 up.rs485_stop_tx = bcm2835aux_rs485_stop_tx; 114 115 /* initialize cached copy with power-on reset value */ 116 data->cntl = BCM2835_AUX_UART_CNTL_RXEN | BCM2835_AUX_UART_CNTL_TXEN; 117 118 platform_set_drvdata(pdev, data); 119 120 /* get the clock - this also enables the HW */ 121 data->clk = devm_clk_get_optional(&pdev->dev, NULL); 122 123 /* get the interrupt */ 124 ret = platform_get_irq(pdev, 0); 125 if (ret < 0) 126 return ret; 127 up.port.irq = ret; 128 129 /* map the main registers */ 130 res = platform_get_resource(pdev, IORESOURCE_MEM, 0); 131 if (!res) { 132 dev_err(&pdev->dev, "memory resource not found"); 133 return -EINVAL; 134 } 135 136 bcm_data = device_get_match_data(&pdev->dev); 137 138 /* Some UEFI implementations (e.g. tianocore/edk2 for the Raspberry Pi) 139 * describe the miniuart with a base address that encompasses the auxiliary 140 * registers shared between the miniuart and spi. 141 * 142 * This is due to historical reasons, see discussion here : 143 * https://edk2.groups.io/g/devel/topic/87501357#84349 144 * 145 * We need to add the offset between the miniuart and auxiliary 146 * registers to get the real miniuart base address. 147 */ 148 if (bcm_data) 149 offset = bcm_data->offset; 150 151 up.port.mapbase = res->start + offset; 152 up.port.mapsize = resource_size(res) - offset; 153 154 /* Check for a fixed line number */ 155 ret = of_alias_get_id(pdev->dev.of_node, "serial"); 156 if (ret >= 0) 157 up.port.line = ret; 158 159 /* enable the clock as a last step */ 160 ret = clk_prepare_enable(data->clk); 161 if (ret) { 162 dev_err(&pdev->dev, "unable to enable uart clock - %d\n", 163 ret); 164 return ret; 165 } 166 167 uartclk = clk_get_rate(data->clk); 168 if (!uartclk) { 169 ret = device_property_read_u32(&pdev->dev, "clock-frequency", &uartclk); 170 if (ret) { 171 dev_err_probe(&pdev->dev, ret, "could not get clk rate\n"); 172 goto dis_clk; 173 } 174 } 175 176 /* the HW-clock divider for bcm2835aux is 8, 177 * but 8250 expects a divider of 16, 178 * so we have to multiply the actual clock by 2 179 * to get identical baudrates. 180 */ 181 up.port.uartclk = uartclk * 2; 182 183 /* register the port */ 184 ret = serial8250_register_8250_port(&up); 185 if (ret < 0) { 186 dev_err_probe(&pdev->dev, ret, "unable to register 8250 port\n"); 187 goto dis_clk; 188 } 189 data->line = ret; 190 191 return 0; 192 193 dis_clk: 194 clk_disable_unprepare(data->clk); 195 return ret; 196 } 197 198 static int bcm2835aux_serial_remove(struct platform_device *pdev) 199 { 200 struct bcm2835aux_data *data = platform_get_drvdata(pdev); 201 202 serial8250_unregister_port(data->line); 203 clk_disable_unprepare(data->clk); 204 205 return 0; 206 } 207 208 static const struct bcm2835_aux_serial_driver_data bcm2835_acpi_data = { 209 .offset = 0x40, 210 }; 211 212 static const struct of_device_id bcm2835aux_serial_match[] = { 213 { .compatible = "brcm,bcm2835-aux-uart" }, 214 { }, 215 }; 216 MODULE_DEVICE_TABLE(of, bcm2835aux_serial_match); 217 218 static const struct acpi_device_id bcm2835aux_serial_acpi_match[] = { 219 { "BCM2836", (kernel_ulong_t)&bcm2835_acpi_data }, 220 { } 221 }; 222 MODULE_DEVICE_TABLE(acpi, bcm2835aux_serial_acpi_match); 223 224 static struct platform_driver bcm2835aux_serial_driver = { 225 .driver = { 226 .name = "bcm2835-aux-uart", 227 .of_match_table = bcm2835aux_serial_match, 228 .acpi_match_table = bcm2835aux_serial_acpi_match, 229 }, 230 .probe = bcm2835aux_serial_probe, 231 .remove = bcm2835aux_serial_remove, 232 }; 233 module_platform_driver(bcm2835aux_serial_driver); 234 235 #ifdef CONFIG_SERIAL_8250_CONSOLE 236 237 static int __init early_bcm2835aux_setup(struct earlycon_device *device, 238 const char *options) 239 { 240 if (!device->port.membase) 241 return -ENODEV; 242 243 device->port.iotype = UPIO_MEM32; 244 device->port.regshift = 2; 245 246 return early_serial8250_setup(device, NULL); 247 } 248 249 OF_EARLYCON_DECLARE(bcm2835aux, "brcm,bcm2835-aux-uart", 250 early_bcm2835aux_setup); 251 #endif 252 253 MODULE_DESCRIPTION("BCM2835 auxiliar UART driver"); 254 MODULE_AUTHOR("Martin Sperl <kernel@martin.sperl.org>"); 255 MODULE_LICENSE("GPL v2"); 256