1 // SPDX-License-Identifier: GPL-2.0+ 2 /* 3 * Serial Port driver for Aspeed VUART device 4 * 5 * Copyright (C) 2016 Jeremy Kerr <jk@ozlabs.org>, IBM Corp. 6 * Copyright (C) 2006 Arnd Bergmann <arnd@arndb.de>, IBM Corp. 7 */ 8 #include <linux/device.h> 9 #include <linux/module.h> 10 #include <linux/of_address.h> 11 #include <linux/of_irq.h> 12 #include <linux/of_platform.h> 13 #include <linux/regmap.h> 14 #include <linux/mfd/syscon.h> 15 #include <linux/tty.h> 16 #include <linux/tty_flip.h> 17 #include <linux/clk.h> 18 19 #include "8250.h" 20 21 #define ASPEED_VUART_GCRA 0x20 22 #define ASPEED_VUART_GCRA_VUART_EN BIT(0) 23 #define ASPEED_VUART_GCRA_HOST_SIRQ_POLARITY BIT(1) 24 #define ASPEED_VUART_GCRA_DISABLE_HOST_TX_DISCARD BIT(5) 25 #define ASPEED_VUART_GCRB 0x24 26 #define ASPEED_VUART_GCRB_HOST_SIRQ_MASK GENMASK(7, 4) 27 #define ASPEED_VUART_GCRB_HOST_SIRQ_SHIFT 4 28 #define ASPEED_VUART_ADDRL 0x28 29 #define ASPEED_VUART_ADDRH 0x2c 30 31 struct aspeed_vuart { 32 struct device *dev; 33 void __iomem *regs; 34 struct clk *clk; 35 int line; 36 struct timer_list unthrottle_timer; 37 struct uart_8250_port *port; 38 }; 39 40 /* 41 * If we fill the tty flip buffers, we throttle the data ready interrupt 42 * to prevent dropped characters. This timeout defines how long we wait 43 * to (conditionally, depending on buffer state) unthrottle. 44 */ 45 static const int unthrottle_timeout = HZ/10; 46 47 /* 48 * The VUART is basically two UART 'front ends' connected by their FIFO 49 * (no actual serial line in between). One is on the BMC side (management 50 * controller) and one is on the host CPU side. 51 * 52 * It allows the BMC to provide to the host a "UART" that pipes into 53 * the BMC itself and can then be turned by the BMC into a network console 54 * of some sort for example. 55 * 56 * This driver is for the BMC side. The sysfs files allow the BMC 57 * userspace which owns the system configuration policy, to specify 58 * at what IO port and interrupt number the host side will appear 59 * to the host on the Host <-> BMC LPC bus. It could be different on a 60 * different system (though most of them use 3f8/4). 61 */ 62 63 static ssize_t lpc_address_show(struct device *dev, 64 struct device_attribute *attr, char *buf) 65 { 66 struct aspeed_vuart *vuart = dev_get_drvdata(dev); 67 u16 addr; 68 69 addr = (readb(vuart->regs + ASPEED_VUART_ADDRH) << 8) | 70 (readb(vuart->regs + ASPEED_VUART_ADDRL)); 71 72 return snprintf(buf, PAGE_SIZE - 1, "0x%x\n", addr); 73 } 74 75 static ssize_t lpc_address_store(struct device *dev, 76 struct device_attribute *attr, 77 const char *buf, size_t count) 78 { 79 struct aspeed_vuart *vuart = dev_get_drvdata(dev); 80 unsigned long val; 81 int err; 82 83 err = kstrtoul(buf, 0, &val); 84 if (err) 85 return err; 86 87 writeb(val >> 8, vuart->regs + ASPEED_VUART_ADDRH); 88 writeb(val >> 0, vuart->regs + ASPEED_VUART_ADDRL); 89 90 return count; 91 } 92 93 static DEVICE_ATTR_RW(lpc_address); 94 95 static ssize_t sirq_show(struct device *dev, 96 struct device_attribute *attr, char *buf) 97 { 98 struct aspeed_vuart *vuart = dev_get_drvdata(dev); 99 u8 reg; 100 101 reg = readb(vuart->regs + ASPEED_VUART_GCRB); 102 reg &= ASPEED_VUART_GCRB_HOST_SIRQ_MASK; 103 reg >>= ASPEED_VUART_GCRB_HOST_SIRQ_SHIFT; 104 105 return snprintf(buf, PAGE_SIZE - 1, "%u\n", reg); 106 } 107 108 static ssize_t sirq_store(struct device *dev, struct device_attribute *attr, 109 const char *buf, size_t count) 110 { 111 struct aspeed_vuart *vuart = dev_get_drvdata(dev); 112 unsigned long val; 113 int err; 114 u8 reg; 115 116 err = kstrtoul(buf, 0, &val); 117 if (err) 118 return err; 119 120 val <<= ASPEED_VUART_GCRB_HOST_SIRQ_SHIFT; 121 val &= ASPEED_VUART_GCRB_HOST_SIRQ_MASK; 122 123 reg = readb(vuart->regs + ASPEED_VUART_GCRB); 124 reg &= ~ASPEED_VUART_GCRB_HOST_SIRQ_MASK; 125 reg |= val; 126 writeb(reg, vuart->regs + ASPEED_VUART_GCRB); 127 128 return count; 129 } 130 131 static DEVICE_ATTR_RW(sirq); 132 133 static ssize_t sirq_polarity_show(struct device *dev, 134 struct device_attribute *attr, char *buf) 135 { 136 struct aspeed_vuart *vuart = dev_get_drvdata(dev); 137 u8 reg; 138 139 reg = readb(vuart->regs + ASPEED_VUART_GCRA); 140 reg &= ASPEED_VUART_GCRA_HOST_SIRQ_POLARITY; 141 142 return snprintf(buf, PAGE_SIZE - 1, "%u\n", reg ? 1 : 0); 143 } 144 145 static void aspeed_vuart_set_sirq_polarity(struct aspeed_vuart *vuart, 146 bool polarity) 147 { 148 u8 reg = readb(vuart->regs + ASPEED_VUART_GCRA); 149 150 if (polarity) 151 reg |= ASPEED_VUART_GCRA_HOST_SIRQ_POLARITY; 152 else 153 reg &= ~ASPEED_VUART_GCRA_HOST_SIRQ_POLARITY; 154 155 writeb(reg, vuart->regs + ASPEED_VUART_GCRA); 156 } 157 158 static ssize_t sirq_polarity_store(struct device *dev, 159 struct device_attribute *attr, 160 const char *buf, size_t count) 161 { 162 struct aspeed_vuart *vuart = dev_get_drvdata(dev); 163 unsigned long val; 164 int err; 165 166 err = kstrtoul(buf, 0, &val); 167 if (err) 168 return err; 169 170 aspeed_vuart_set_sirq_polarity(vuart, val != 0); 171 172 return count; 173 } 174 175 static DEVICE_ATTR_RW(sirq_polarity); 176 177 static struct attribute *aspeed_vuart_attrs[] = { 178 &dev_attr_sirq.attr, 179 &dev_attr_sirq_polarity.attr, 180 &dev_attr_lpc_address.attr, 181 NULL, 182 }; 183 184 static const struct attribute_group aspeed_vuart_attr_group = { 185 .attrs = aspeed_vuart_attrs, 186 }; 187 188 static void aspeed_vuart_set_enabled(struct aspeed_vuart *vuart, bool enabled) 189 { 190 u8 reg = readb(vuart->regs + ASPEED_VUART_GCRA); 191 192 if (enabled) 193 reg |= ASPEED_VUART_GCRA_VUART_EN; 194 else 195 reg &= ~ASPEED_VUART_GCRA_VUART_EN; 196 197 writeb(reg, vuart->regs + ASPEED_VUART_GCRA); 198 } 199 200 static void aspeed_vuart_set_host_tx_discard(struct aspeed_vuart *vuart, 201 bool discard) 202 { 203 u8 reg; 204 205 reg = readb(vuart->regs + ASPEED_VUART_GCRA); 206 207 /* If the DISABLE_HOST_TX_DISCARD bit is set, discard is disabled */ 208 if (!discard) 209 reg |= ASPEED_VUART_GCRA_DISABLE_HOST_TX_DISCARD; 210 else 211 reg &= ~ASPEED_VUART_GCRA_DISABLE_HOST_TX_DISCARD; 212 213 writeb(reg, vuart->regs + ASPEED_VUART_GCRA); 214 } 215 216 static int aspeed_vuart_startup(struct uart_port *uart_port) 217 { 218 struct uart_8250_port *uart_8250_port = up_to_u8250p(uart_port); 219 struct aspeed_vuart *vuart = uart_8250_port->port.private_data; 220 int rc; 221 222 rc = serial8250_do_startup(uart_port); 223 if (rc) 224 return rc; 225 226 aspeed_vuart_set_host_tx_discard(vuart, false); 227 228 return 0; 229 } 230 231 static void aspeed_vuart_shutdown(struct uart_port *uart_port) 232 { 233 struct uart_8250_port *uart_8250_port = up_to_u8250p(uart_port); 234 struct aspeed_vuart *vuart = uart_8250_port->port.private_data; 235 236 aspeed_vuart_set_host_tx_discard(vuart, true); 237 238 serial8250_do_shutdown(uart_port); 239 } 240 241 static void __aspeed_vuart_set_throttle(struct uart_8250_port *up, 242 bool throttle) 243 { 244 unsigned char irqs = UART_IER_RLSI | UART_IER_RDI; 245 246 up->ier &= ~irqs; 247 if (!throttle) 248 up->ier |= irqs; 249 serial_out(up, UART_IER, up->ier); 250 } 251 static void aspeed_vuart_set_throttle(struct uart_port *port, bool throttle) 252 { 253 struct uart_8250_port *up = up_to_u8250p(port); 254 unsigned long flags; 255 256 spin_lock_irqsave(&port->lock, flags); 257 __aspeed_vuart_set_throttle(up, throttle); 258 spin_unlock_irqrestore(&port->lock, flags); 259 } 260 261 static void aspeed_vuart_throttle(struct uart_port *port) 262 { 263 aspeed_vuart_set_throttle(port, true); 264 } 265 266 static void aspeed_vuart_unthrottle(struct uart_port *port) 267 { 268 aspeed_vuart_set_throttle(port, false); 269 } 270 271 static void aspeed_vuart_unthrottle_exp(struct timer_list *timer) 272 { 273 struct aspeed_vuart *vuart = from_timer(vuart, timer, unthrottle_timer); 274 struct uart_8250_port *up = vuart->port; 275 276 if (!tty_buffer_space_avail(&up->port.state->port)) { 277 mod_timer(&vuart->unthrottle_timer, 278 jiffies + unthrottle_timeout); 279 return; 280 } 281 282 aspeed_vuart_unthrottle(&up->port); 283 } 284 285 /* 286 * Custom interrupt handler to manage finer-grained flow control. Although we 287 * have throttle/unthrottle callbacks, we've seen that the VUART device can 288 * deliver characters faster than the ldisc has a chance to check buffer space 289 * against the throttle threshold. This results in dropped characters before 290 * the throttle. 291 * 292 * We do this by checking for flip buffer space before RX. If we have no space, 293 * throttle now and schedule an unthrottle for later, once the ldisc has had 294 * a chance to drain the buffers. 295 */ 296 static int aspeed_vuart_handle_irq(struct uart_port *port) 297 { 298 struct uart_8250_port *up = up_to_u8250p(port); 299 unsigned int iir, lsr; 300 unsigned long flags; 301 int space, count; 302 303 iir = serial_port_in(port, UART_IIR); 304 305 if (iir & UART_IIR_NO_INT) 306 return 0; 307 308 spin_lock_irqsave(&port->lock, flags); 309 310 lsr = serial_port_in(port, UART_LSR); 311 312 if (lsr & (UART_LSR_DR | UART_LSR_BI)) { 313 space = tty_buffer_space_avail(&port->state->port); 314 315 if (!space) { 316 /* throttle and schedule an unthrottle later */ 317 struct aspeed_vuart *vuart = port->private_data; 318 __aspeed_vuart_set_throttle(up, true); 319 320 if (!timer_pending(&vuart->unthrottle_timer)) { 321 vuart->port = up; 322 mod_timer(&vuart->unthrottle_timer, 323 jiffies + unthrottle_timeout); 324 } 325 326 } else { 327 count = min(space, 256); 328 329 do { 330 serial8250_read_char(up, lsr); 331 lsr = serial_in(up, UART_LSR); 332 if (--count == 0) 333 break; 334 } while (lsr & (UART_LSR_DR | UART_LSR_BI)); 335 336 tty_flip_buffer_push(&port->state->port); 337 } 338 } 339 340 serial8250_modem_status(up); 341 if (lsr & UART_LSR_THRE) 342 serial8250_tx_chars(up); 343 344 uart_unlock_and_check_sysrq(port, flags); 345 346 return 1; 347 } 348 349 static void aspeed_vuart_auto_configure_sirq_polarity( 350 struct aspeed_vuart *vuart, struct device_node *syscon_np, 351 u32 reg_offset, u32 reg_mask) 352 { 353 struct regmap *regmap; 354 u32 value; 355 356 regmap = syscon_node_to_regmap(syscon_np); 357 if (IS_ERR(regmap)) { 358 dev_warn(vuart->dev, 359 "could not get regmap for aspeed,sirq-polarity-sense\n"); 360 return; 361 } 362 if (regmap_read(regmap, reg_offset, &value)) { 363 dev_warn(vuart->dev, "could not read hw strap table\n"); 364 return; 365 } 366 367 aspeed_vuart_set_sirq_polarity(vuart, (value & reg_mask) == 0); 368 } 369 370 static int aspeed_vuart_probe(struct platform_device *pdev) 371 { 372 struct of_phandle_args sirq_polarity_sense_args; 373 struct uart_8250_port port; 374 struct aspeed_vuart *vuart; 375 struct device_node *np; 376 struct resource *res; 377 u32 clk, prop; 378 int rc; 379 380 np = pdev->dev.of_node; 381 382 vuart = devm_kzalloc(&pdev->dev, sizeof(*vuart), GFP_KERNEL); 383 if (!vuart) 384 return -ENOMEM; 385 386 vuart->dev = &pdev->dev; 387 timer_setup(&vuart->unthrottle_timer, aspeed_vuart_unthrottle_exp, 0); 388 389 res = platform_get_resource(pdev, IORESOURCE_MEM, 0); 390 vuart->regs = devm_ioremap_resource(&pdev->dev, res); 391 if (IS_ERR(vuart->regs)) 392 return PTR_ERR(vuart->regs); 393 394 memset(&port, 0, sizeof(port)); 395 port.port.private_data = vuart; 396 port.port.membase = vuart->regs; 397 port.port.mapbase = res->start; 398 port.port.mapsize = resource_size(res); 399 port.port.startup = aspeed_vuart_startup; 400 port.port.shutdown = aspeed_vuart_shutdown; 401 port.port.throttle = aspeed_vuart_throttle; 402 port.port.unthrottle = aspeed_vuart_unthrottle; 403 port.port.status = UPSTAT_SYNC_FIFO; 404 port.port.dev = &pdev->dev; 405 port.port.has_sysrq = IS_ENABLED(CONFIG_SERIAL_8250_CONSOLE); 406 407 rc = sysfs_create_group(&vuart->dev->kobj, &aspeed_vuart_attr_group); 408 if (rc < 0) 409 return rc; 410 411 if (of_property_read_u32(np, "clock-frequency", &clk)) { 412 vuart->clk = devm_clk_get(&pdev->dev, NULL); 413 if (IS_ERR(vuart->clk)) { 414 dev_warn(&pdev->dev, 415 "clk or clock-frequency not defined\n"); 416 rc = PTR_ERR(vuart->clk); 417 goto err_sysfs_remove; 418 } 419 420 rc = clk_prepare_enable(vuart->clk); 421 if (rc < 0) 422 goto err_sysfs_remove; 423 424 clk = clk_get_rate(vuart->clk); 425 } 426 427 /* If current-speed was set, then try not to change it. */ 428 if (of_property_read_u32(np, "current-speed", &prop) == 0) 429 port.port.custom_divisor = clk / (16 * prop); 430 431 /* Check for shifted address mapping */ 432 if (of_property_read_u32(np, "reg-offset", &prop) == 0) 433 port.port.mapbase += prop; 434 435 /* Check for registers offset within the devices address range */ 436 if (of_property_read_u32(np, "reg-shift", &prop) == 0) 437 port.port.regshift = prop; 438 439 /* Check for fifo size */ 440 if (of_property_read_u32(np, "fifo-size", &prop) == 0) 441 port.port.fifosize = prop; 442 443 /* Check for a fixed line number */ 444 rc = of_alias_get_id(np, "serial"); 445 if (rc >= 0) 446 port.port.line = rc; 447 448 port.port.irq = irq_of_parse_and_map(np, 0); 449 port.port.handle_irq = aspeed_vuart_handle_irq; 450 port.port.iotype = UPIO_MEM; 451 port.port.type = PORT_16550A; 452 port.port.uartclk = clk; 453 port.port.flags = UPF_SHARE_IRQ | UPF_BOOT_AUTOCONF 454 | UPF_FIXED_PORT | UPF_FIXED_TYPE | UPF_NO_THRE_TEST; 455 456 if (of_property_read_bool(np, "no-loopback-test")) 457 port.port.flags |= UPF_SKIP_TEST; 458 459 if (port.port.fifosize) 460 port.capabilities = UART_CAP_FIFO; 461 462 if (of_property_read_bool(np, "auto-flow-control")) 463 port.capabilities |= UART_CAP_AFE; 464 465 rc = serial8250_register_8250_port(&port); 466 if (rc < 0) 467 goto err_clk_disable; 468 469 vuart->line = rc; 470 471 rc = of_parse_phandle_with_fixed_args( 472 np, "aspeed,sirq-polarity-sense", 2, 0, 473 &sirq_polarity_sense_args); 474 if (rc < 0) { 475 dev_dbg(&pdev->dev, 476 "aspeed,sirq-polarity-sense property not found\n"); 477 } else { 478 aspeed_vuart_auto_configure_sirq_polarity( 479 vuart, sirq_polarity_sense_args.np, 480 sirq_polarity_sense_args.args[0], 481 BIT(sirq_polarity_sense_args.args[1])); 482 of_node_put(sirq_polarity_sense_args.np); 483 } 484 485 aspeed_vuart_set_enabled(vuart, true); 486 aspeed_vuart_set_host_tx_discard(vuart, true); 487 platform_set_drvdata(pdev, vuart); 488 489 return 0; 490 491 err_clk_disable: 492 clk_disable_unprepare(vuart->clk); 493 irq_dispose_mapping(port.port.irq); 494 err_sysfs_remove: 495 sysfs_remove_group(&vuart->dev->kobj, &aspeed_vuart_attr_group); 496 return rc; 497 } 498 499 static int aspeed_vuart_remove(struct platform_device *pdev) 500 { 501 struct aspeed_vuart *vuart = platform_get_drvdata(pdev); 502 503 del_timer_sync(&vuart->unthrottle_timer); 504 aspeed_vuart_set_enabled(vuart, false); 505 serial8250_unregister_port(vuart->line); 506 sysfs_remove_group(&vuart->dev->kobj, &aspeed_vuart_attr_group); 507 clk_disable_unprepare(vuart->clk); 508 509 return 0; 510 } 511 512 static const struct of_device_id aspeed_vuart_table[] = { 513 { .compatible = "aspeed,ast2400-vuart" }, 514 { .compatible = "aspeed,ast2500-vuart" }, 515 { }, 516 }; 517 518 static struct platform_driver aspeed_vuart_driver = { 519 .driver = { 520 .name = "aspeed-vuart", 521 .of_match_table = aspeed_vuart_table, 522 }, 523 .probe = aspeed_vuart_probe, 524 .remove = aspeed_vuart_remove, 525 }; 526 527 module_platform_driver(aspeed_vuart_driver); 528 529 MODULE_AUTHOR("Jeremy Kerr <jk@ozlabs.org>"); 530 MODULE_LICENSE("GPL"); 531 MODULE_DESCRIPTION("Driver for Aspeed VUART device"); 532