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 #define ASPEED_VUART_DEFAULT_LPC_ADDR 0x3f8 32 #define ASPEED_VUART_DEFAULT_SIRQ 4 33 #define ASPEED_VUART_DEFAULT_SIRQ_POLARITY IRQ_TYPE_LEVEL_LOW 34 35 struct aspeed_vuart { 36 struct device *dev; 37 int line; 38 struct timer_list unthrottle_timer; 39 struct uart_8250_port *port; 40 }; 41 42 /* 43 * If we fill the tty flip buffers, we throttle the data ready interrupt 44 * to prevent dropped characters. This timeout defines how long we wait 45 * to (conditionally, depending on buffer state) unthrottle. 46 */ 47 static const int unthrottle_timeout = HZ/10; 48 49 /* 50 * The VUART is basically two UART 'front ends' connected by their FIFO 51 * (no actual serial line in between). One is on the BMC side (management 52 * controller) and one is on the host CPU side. 53 * 54 * It allows the BMC to provide to the host a "UART" that pipes into 55 * the BMC itself and can then be turned by the BMC into a network console 56 * of some sort for example. 57 * 58 * This driver is for the BMC side. The sysfs files allow the BMC 59 * userspace which owns the system configuration policy, to specify 60 * at what IO port and interrupt number the host side will appear 61 * to the host on the Host <-> BMC LPC bus. It could be different on a 62 * different system (though most of them use 3f8/4). 63 */ 64 65 static inline u8 aspeed_vuart_readb(struct aspeed_vuart *vuart, u8 reg) 66 { 67 return readb(vuart->port->port.membase + reg); 68 } 69 70 static inline void aspeed_vuart_writeb(struct aspeed_vuart *vuart, u8 val, u8 reg) 71 { 72 writeb(val, vuart->port->port.membase + reg); 73 } 74 75 static ssize_t lpc_address_show(struct device *dev, 76 struct device_attribute *attr, char *buf) 77 { 78 struct aspeed_vuart *vuart = dev_get_drvdata(dev); 79 u16 addr; 80 81 addr = (aspeed_vuart_readb(vuart, ASPEED_VUART_ADDRH) << 8) | 82 (aspeed_vuart_readb(vuart, ASPEED_VUART_ADDRL)); 83 84 return sysfs_emit(buf, "0x%x\n", addr); 85 } 86 87 static int aspeed_vuart_set_lpc_address(struct aspeed_vuart *vuart, u32 addr) 88 { 89 if (addr > U16_MAX) 90 return -EINVAL; 91 92 aspeed_vuart_writeb(vuart, addr >> 8, ASPEED_VUART_ADDRH); 93 aspeed_vuart_writeb(vuart, addr >> 0, ASPEED_VUART_ADDRL); 94 95 return 0; 96 } 97 98 static ssize_t lpc_address_store(struct device *dev, 99 struct device_attribute *attr, 100 const char *buf, size_t count) 101 { 102 struct aspeed_vuart *vuart = dev_get_drvdata(dev); 103 u32 val; 104 int err; 105 106 err = kstrtou32(buf, 0, &val); 107 if (err) 108 return err; 109 110 err = aspeed_vuart_set_lpc_address(vuart, val); 111 return err ? : count; 112 } 113 114 static DEVICE_ATTR_RW(lpc_address); 115 116 static ssize_t sirq_show(struct device *dev, 117 struct device_attribute *attr, char *buf) 118 { 119 struct aspeed_vuart *vuart = dev_get_drvdata(dev); 120 u8 reg; 121 122 reg = aspeed_vuart_readb(vuart, ASPEED_VUART_GCRB); 123 reg &= ASPEED_VUART_GCRB_HOST_SIRQ_MASK; 124 reg >>= ASPEED_VUART_GCRB_HOST_SIRQ_SHIFT; 125 126 return sysfs_emit(buf, "%u\n", reg); 127 } 128 129 static int aspeed_vuart_set_sirq(struct aspeed_vuart *vuart, u32 sirq) 130 { 131 u8 reg; 132 133 if (sirq > (ASPEED_VUART_GCRB_HOST_SIRQ_MASK >> ASPEED_VUART_GCRB_HOST_SIRQ_SHIFT)) 134 return -EINVAL; 135 136 sirq <<= ASPEED_VUART_GCRB_HOST_SIRQ_SHIFT; 137 sirq &= ASPEED_VUART_GCRB_HOST_SIRQ_MASK; 138 139 reg = aspeed_vuart_readb(vuart, ASPEED_VUART_GCRB); 140 reg &= ~ASPEED_VUART_GCRB_HOST_SIRQ_MASK; 141 reg |= sirq; 142 aspeed_vuart_writeb(vuart, reg, ASPEED_VUART_GCRB); 143 144 return 0; 145 } 146 147 static ssize_t sirq_store(struct device *dev, struct device_attribute *attr, 148 const char *buf, size_t count) 149 { 150 struct aspeed_vuart *vuart = dev_get_drvdata(dev); 151 unsigned long val; 152 int err; 153 154 err = kstrtoul(buf, 0, &val); 155 if (err) 156 return err; 157 158 err = aspeed_vuart_set_sirq(vuart, val); 159 return err ? : count; 160 } 161 162 static DEVICE_ATTR_RW(sirq); 163 164 static ssize_t sirq_polarity_show(struct device *dev, 165 struct device_attribute *attr, char *buf) 166 { 167 struct aspeed_vuart *vuart = dev_get_drvdata(dev); 168 u8 reg; 169 170 reg = aspeed_vuart_readb(vuart, ASPEED_VUART_GCRA); 171 reg &= ASPEED_VUART_GCRA_HOST_SIRQ_POLARITY; 172 173 return sysfs_emit(buf, "%u\n", reg ? 1 : 0); 174 } 175 176 static void aspeed_vuart_set_sirq_polarity(struct aspeed_vuart *vuart, 177 bool polarity) 178 { 179 u8 reg = aspeed_vuart_readb(vuart, ASPEED_VUART_GCRA); 180 181 if (polarity) 182 reg |= ASPEED_VUART_GCRA_HOST_SIRQ_POLARITY; 183 else 184 reg &= ~ASPEED_VUART_GCRA_HOST_SIRQ_POLARITY; 185 186 aspeed_vuart_writeb(vuart, reg, ASPEED_VUART_GCRA); 187 } 188 189 static ssize_t sirq_polarity_store(struct device *dev, 190 struct device_attribute *attr, 191 const char *buf, size_t count) 192 { 193 struct aspeed_vuart *vuart = dev_get_drvdata(dev); 194 unsigned long val; 195 int err; 196 197 err = kstrtoul(buf, 0, &val); 198 if (err) 199 return err; 200 201 aspeed_vuart_set_sirq_polarity(vuart, val != 0); 202 203 return count; 204 } 205 206 static DEVICE_ATTR_RW(sirq_polarity); 207 208 static struct attribute *aspeed_vuart_attrs[] = { 209 &dev_attr_sirq.attr, 210 &dev_attr_sirq_polarity.attr, 211 &dev_attr_lpc_address.attr, 212 NULL, 213 }; 214 215 static const struct attribute_group aspeed_vuart_attr_group = { 216 .attrs = aspeed_vuart_attrs, 217 }; 218 219 static void aspeed_vuart_set_enabled(struct aspeed_vuart *vuart, bool enabled) 220 { 221 u8 reg = aspeed_vuart_readb(vuart, ASPEED_VUART_GCRA); 222 223 if (enabled) 224 reg |= ASPEED_VUART_GCRA_VUART_EN; 225 else 226 reg &= ~ASPEED_VUART_GCRA_VUART_EN; 227 228 aspeed_vuart_writeb(vuart, reg, ASPEED_VUART_GCRA); 229 } 230 231 static void aspeed_vuart_set_host_tx_discard(struct aspeed_vuart *vuart, 232 bool discard) 233 { 234 u8 reg; 235 236 reg = aspeed_vuart_readb(vuart, ASPEED_VUART_GCRA); 237 238 /* If the DISABLE_HOST_TX_DISCARD bit is set, discard is disabled */ 239 if (!discard) 240 reg |= ASPEED_VUART_GCRA_DISABLE_HOST_TX_DISCARD; 241 else 242 reg &= ~ASPEED_VUART_GCRA_DISABLE_HOST_TX_DISCARD; 243 244 aspeed_vuart_writeb(vuart, reg, ASPEED_VUART_GCRA); 245 } 246 247 static int aspeed_vuart_startup(struct uart_port *uart_port) 248 { 249 struct uart_8250_port *uart_8250_port = up_to_u8250p(uart_port); 250 struct aspeed_vuart *vuart = uart_8250_port->port.private_data; 251 int rc; 252 253 rc = serial8250_do_startup(uart_port); 254 if (rc) 255 return rc; 256 257 aspeed_vuart_set_host_tx_discard(vuart, false); 258 259 return 0; 260 } 261 262 static void aspeed_vuart_shutdown(struct uart_port *uart_port) 263 { 264 struct uart_8250_port *uart_8250_port = up_to_u8250p(uart_port); 265 struct aspeed_vuart *vuart = uart_8250_port->port.private_data; 266 267 aspeed_vuart_set_host_tx_discard(vuart, true); 268 269 serial8250_do_shutdown(uart_port); 270 } 271 272 static void __aspeed_vuart_set_throttle(struct uart_8250_port *up, 273 bool throttle) 274 { 275 unsigned char irqs = UART_IER_RLSI | UART_IER_RDI; 276 277 /* Port locked to synchronize UART_IER access against the console. */ 278 lockdep_assert_held_once(&up->port.lock); 279 280 up->ier &= ~irqs; 281 if (!throttle) 282 up->ier |= irqs; 283 serial_out(up, UART_IER, up->ier); 284 } 285 static void aspeed_vuart_set_throttle(struct uart_port *port, bool throttle) 286 { 287 struct uart_8250_port *up = up_to_u8250p(port); 288 unsigned long flags; 289 290 uart_port_lock_irqsave(port, &flags); 291 __aspeed_vuart_set_throttle(up, throttle); 292 uart_port_unlock_irqrestore(port, flags); 293 } 294 295 static void aspeed_vuart_throttle(struct uart_port *port) 296 { 297 aspeed_vuart_set_throttle(port, true); 298 } 299 300 static void aspeed_vuart_unthrottle(struct uart_port *port) 301 { 302 aspeed_vuart_set_throttle(port, false); 303 } 304 305 static void aspeed_vuart_unthrottle_exp(struct timer_list *timer) 306 { 307 struct aspeed_vuart *vuart = timer_container_of(vuart, timer, 308 unthrottle_timer); 309 struct uart_8250_port *up = vuart->port; 310 311 if (!tty_buffer_space_avail(&up->port.state->port)) { 312 mod_timer(&vuart->unthrottle_timer, 313 jiffies + unthrottle_timeout); 314 return; 315 } 316 317 aspeed_vuart_unthrottle(&up->port); 318 } 319 320 /* 321 * Custom interrupt handler to manage finer-grained flow control. Although we 322 * have throttle/unthrottle callbacks, we've seen that the VUART device can 323 * deliver characters faster than the ldisc has a chance to check buffer space 324 * against the throttle threshold. This results in dropped characters before 325 * the throttle. 326 * 327 * We do this by checking for flip buffer space before RX. If we have no space, 328 * throttle now and schedule an unthrottle for later, once the ldisc has had 329 * a chance to drain the buffers. 330 */ 331 static int aspeed_vuart_handle_irq(struct uart_port *port) 332 { 333 struct uart_8250_port *up = up_to_u8250p(port); 334 unsigned int iir, lsr; 335 unsigned long flags; 336 unsigned int space, count; 337 338 iir = serial_port_in(port, UART_IIR); 339 340 if (iir & UART_IIR_NO_INT) 341 return 0; 342 343 uart_port_lock_irqsave(port, &flags); 344 345 lsr = serial_port_in(port, UART_LSR); 346 347 if (lsr & (UART_LSR_DR | UART_LSR_BI)) { 348 space = tty_buffer_space_avail(&port->state->port); 349 350 if (!space) { 351 /* throttle and schedule an unthrottle later */ 352 struct aspeed_vuart *vuart = port->private_data; 353 __aspeed_vuart_set_throttle(up, true); 354 355 if (!timer_pending(&vuart->unthrottle_timer)) 356 mod_timer(&vuart->unthrottle_timer, 357 jiffies + unthrottle_timeout); 358 359 } else { 360 count = min(space, 256U); 361 362 do { 363 serial8250_read_char(up, lsr); 364 lsr = serial_in(up, UART_LSR); 365 if (--count == 0) 366 break; 367 } while (lsr & (UART_LSR_DR | UART_LSR_BI)); 368 369 tty_flip_buffer_push(&port->state->port); 370 } 371 } 372 373 serial8250_modem_status(up); 374 if (lsr & UART_LSR_THRE) 375 serial8250_tx_chars(up); 376 377 uart_unlock_and_check_sysrq_irqrestore(port, flags); 378 379 return 1; 380 } 381 382 static void aspeed_vuart_auto_configure_sirq_polarity( 383 struct aspeed_vuart *vuart, struct device_node *syscon_np, 384 u32 reg_offset, u32 reg_mask) 385 { 386 struct regmap *regmap; 387 u32 value; 388 389 regmap = syscon_node_to_regmap(syscon_np); 390 if (IS_ERR(regmap)) { 391 dev_warn(vuart->dev, 392 "could not get regmap for aspeed,sirq-polarity-sense\n"); 393 return; 394 } 395 if (regmap_read(regmap, reg_offset, &value)) { 396 dev_warn(vuart->dev, "could not read hw strap table\n"); 397 return; 398 } 399 400 aspeed_vuart_set_sirq_polarity(vuart, (value & reg_mask) == 0); 401 } 402 403 static int aspeed_vuart_map_irq_polarity(u32 dt) 404 { 405 switch (dt) { 406 case IRQ_TYPE_LEVEL_LOW: 407 return 0; 408 case IRQ_TYPE_LEVEL_HIGH: 409 return 1; 410 default: 411 return -EINVAL; 412 } 413 } 414 415 static int aspeed_vuart_probe(struct platform_device *pdev) 416 { 417 struct of_phandle_args sirq_polarity_sense_args; 418 struct device *dev = &pdev->dev; 419 struct uart_8250_port port; 420 struct aspeed_vuart *vuart; 421 struct device_node *np; 422 struct resource *res; 423 int rc, sirq_polarity; 424 u32 prop, sirq[2]; 425 struct clk *vclk; 426 427 np = pdev->dev.of_node; 428 429 vuart = devm_kzalloc(&pdev->dev, sizeof(*vuart), GFP_KERNEL); 430 if (!vuart) 431 return -ENOMEM; 432 433 vuart->dev = &pdev->dev; 434 timer_setup(&vuart->unthrottle_timer, aspeed_vuart_unthrottle_exp, 0); 435 436 res = platform_get_resource(pdev, IORESOURCE_MEM, 0); 437 if (!res) 438 return -EINVAL; 439 440 memset(&port, 0, sizeof(port)); 441 port.port.private_data = vuart; 442 port.port.mapbase = res->start; 443 port.port.mapsize = resource_size(res); 444 port.port.startup = aspeed_vuart_startup; 445 port.port.shutdown = aspeed_vuart_shutdown; 446 port.port.throttle = aspeed_vuart_throttle; 447 port.port.unthrottle = aspeed_vuart_unthrottle; 448 port.port.status = UPSTAT_SYNC_FIFO; 449 port.port.dev = &pdev->dev; 450 port.port.has_sysrq = IS_ENABLED(CONFIG_SERIAL_8250_CONSOLE); 451 port.port.flags = UPF_BOOT_AUTOCONF | UPF_IOREMAP | UPF_FIXED_PORT | UPF_FIXED_TYPE | 452 UPF_NO_THRE_TEST; 453 port.bugs |= UART_BUG_TXRACE; 454 455 rc = sysfs_create_group(&vuart->dev->kobj, &aspeed_vuart_attr_group); 456 if (rc < 0) 457 return rc; 458 459 rc = uart_read_port_properties(&port.port); 460 if (rc) 461 goto err_sysfs_remove; 462 463 /* Get clk rate through clk driver if present */ 464 if (!port.port.uartclk) { 465 vclk = devm_clk_get_enabled(dev, NULL); 466 if (IS_ERR(vclk)) { 467 rc = dev_err_probe(dev, PTR_ERR(vclk), "clk or clock-frequency not defined\n"); 468 goto err_sysfs_remove; 469 } 470 471 port.port.uartclk = clk_get_rate(vclk); 472 } 473 474 /* If current-speed was set, then try not to change it. */ 475 if (of_property_read_u32(np, "current-speed", &prop) == 0) 476 port.port.custom_divisor = port.port.uartclk / (16 * prop); 477 478 port.port.handle_irq = aspeed_vuart_handle_irq; 479 port.port.type = PORT_ASPEED_VUART; 480 481 if (port.port.fifosize) 482 port.capabilities = UART_CAP_FIFO; 483 484 if (of_property_read_bool(np, "auto-flow-control")) 485 port.capabilities |= UART_CAP_AFE; 486 487 rc = serial8250_register_8250_port(&port); 488 if (rc < 0) 489 goto err_sysfs_remove; 490 491 vuart->line = rc; 492 vuart->port = serial8250_get_port(vuart->line); 493 494 rc = of_parse_phandle_with_fixed_args( 495 np, "aspeed,sirq-polarity-sense", 2, 0, 496 &sirq_polarity_sense_args); 497 if (rc < 0) { 498 dev_dbg(&pdev->dev, 499 "aspeed,sirq-polarity-sense property not found\n"); 500 } else { 501 aspeed_vuart_auto_configure_sirq_polarity( 502 vuart, sirq_polarity_sense_args.np, 503 sirq_polarity_sense_args.args[0], 504 BIT(sirq_polarity_sense_args.args[1])); 505 of_node_put(sirq_polarity_sense_args.np); 506 } 507 508 rc = of_property_read_u32(np, "aspeed,lpc-io-reg", &prop); 509 if (rc < 0) 510 prop = ASPEED_VUART_DEFAULT_LPC_ADDR; 511 512 rc = aspeed_vuart_set_lpc_address(vuart, prop); 513 if (rc < 0) { 514 dev_err_probe(dev, rc, "invalid value in aspeed,lpc-io-reg property\n"); 515 goto err_sysfs_remove; 516 } 517 518 rc = of_property_read_u32_array(np, "aspeed,lpc-interrupts", sirq, 2); 519 if (rc < 0) { 520 sirq[0] = ASPEED_VUART_DEFAULT_SIRQ; 521 sirq[1] = ASPEED_VUART_DEFAULT_SIRQ_POLARITY; 522 } 523 524 rc = aspeed_vuart_set_sirq(vuart, sirq[0]); 525 if (rc < 0) { 526 dev_err_probe(dev, rc, "invalid sirq number in aspeed,lpc-interrupts property\n"); 527 goto err_sysfs_remove; 528 } 529 530 sirq_polarity = aspeed_vuart_map_irq_polarity(sirq[1]); 531 if (sirq_polarity < 0) { 532 rc = dev_err_probe(dev, sirq_polarity, 533 "invalid sirq polarity in aspeed,lpc-interrupts property\n"); 534 goto err_sysfs_remove; 535 } 536 537 aspeed_vuart_set_sirq_polarity(vuart, sirq_polarity); 538 539 aspeed_vuart_set_enabled(vuart, true); 540 aspeed_vuart_set_host_tx_discard(vuart, true); 541 platform_set_drvdata(pdev, vuart); 542 543 return 0; 544 545 err_sysfs_remove: 546 sysfs_remove_group(&vuart->dev->kobj, &aspeed_vuart_attr_group); 547 return rc; 548 } 549 550 static void aspeed_vuart_remove(struct platform_device *pdev) 551 { 552 struct aspeed_vuart *vuart = platform_get_drvdata(pdev); 553 554 timer_delete_sync(&vuart->unthrottle_timer); 555 aspeed_vuart_set_enabled(vuart, false); 556 serial8250_unregister_port(vuart->line); 557 sysfs_remove_group(&vuart->dev->kobj, &aspeed_vuart_attr_group); 558 } 559 560 static const struct of_device_id aspeed_vuart_table[] = { 561 { .compatible = "aspeed,ast2400-vuart" }, 562 { .compatible = "aspeed,ast2500-vuart" }, 563 { }, 564 }; 565 MODULE_DEVICE_TABLE(of, aspeed_vuart_table); 566 567 static struct platform_driver aspeed_vuart_driver = { 568 .driver = { 569 .name = "aspeed-vuart", 570 .of_match_table = aspeed_vuart_table, 571 }, 572 .probe = aspeed_vuart_probe, 573 .remove = aspeed_vuart_remove, 574 }; 575 576 module_platform_driver(aspeed_vuart_driver); 577 578 MODULE_AUTHOR("Jeremy Kerr <jk@ozlabs.org>"); 579 MODULE_LICENSE("GPL"); 580 MODULE_DESCRIPTION("Driver for Aspeed VUART device"); 581