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 31struct 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 */ 45static 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 63static 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 75static 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 93static DEVICE_ATTR_RW(lpc_address); 94 95static 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 108static 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 131static DEVICE_ATTR_RW(sirq); 132 133static 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 145static 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 158static 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 175static DEVICE_ATTR_RW(sirq_polarity); 176 177static 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 184static const struct attribute_group aspeed_vuart_attr_group = { 185 .attrs = aspeed_vuart_attrs, 186}; 187 188static 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 200static 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 216static 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 231static 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 241static 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} 251static 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 261static void aspeed_vuart_throttle(struct uart_port *port) 262{ 263 aspeed_vuart_set_throttle(port, true); 264} 265 266static void aspeed_vuart_unthrottle(struct uart_port *port) 267{ 268 aspeed_vuart_set_throttle(port, false); 269} 270 271static 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 */ 296static 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 349static 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 370static 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 port.bugs |= UART_BUG_TXRACE; 407 408 rc = sysfs_create_group(&vuart->dev->kobj, &aspeed_vuart_attr_group); 409 if (rc < 0) 410 return rc; 411 412 if (of_property_read_u32(np, "clock-frequency", &clk)) { 413 vuart->clk = devm_clk_get(&pdev->dev, NULL); 414 if (IS_ERR(vuart->clk)) { 415 dev_warn(&pdev->dev, 416 "clk or clock-frequency not defined\n"); 417 rc = PTR_ERR(vuart->clk); 418 goto err_sysfs_remove; 419 } 420 421 rc = clk_prepare_enable(vuart->clk); 422 if (rc < 0) 423 goto err_sysfs_remove; 424 425 clk = clk_get_rate(vuart->clk); 426 } 427 428 /* If current-speed was set, then try not to change it. */ 429 if (of_property_read_u32(np, "current-speed", &prop) == 0) 430 port.port.custom_divisor = clk / (16 * prop); 431 432 /* Check for shifted address mapping */ 433 if (of_property_read_u32(np, "reg-offset", &prop) == 0) 434 port.port.mapbase += prop; 435 436 /* Check for registers offset within the devices address range */ 437 if (of_property_read_u32(np, "reg-shift", &prop) == 0) 438 port.port.regshift = prop; 439 440 /* Check for fifo size */ 441 if (of_property_read_u32(np, "fifo-size", &prop) == 0) 442 port.port.fifosize = prop; 443 444 /* Check for a fixed line number */ 445 rc = of_alias_get_id(np, "serial"); 446 if (rc >= 0) 447 port.port.line = rc; 448 449 port.port.irq = irq_of_parse_and_map(np, 0); 450 port.port.handle_irq = aspeed_vuart_handle_irq; 451 port.port.iotype = UPIO_MEM; 452 port.port.type = PORT_16550A; 453 port.port.uartclk = clk; 454 port.port.flags = UPF_SHARE_IRQ | UPF_BOOT_AUTOCONF 455 | UPF_FIXED_PORT | UPF_FIXED_TYPE | UPF_NO_THRE_TEST; 456 457 if (of_property_read_bool(np, "no-loopback-test")) 458 port.port.flags |= UPF_SKIP_TEST; 459 460 if (port.port.fifosize) 461 port.capabilities = UART_CAP_FIFO; 462 463 if (of_property_read_bool(np, "auto-flow-control")) 464 port.capabilities |= UART_CAP_AFE; 465 466 rc = serial8250_register_8250_port(&port); 467 if (rc < 0) 468 goto err_clk_disable; 469 470 vuart->line = rc; 471 472 rc = of_parse_phandle_with_fixed_args( 473 np, "aspeed,sirq-polarity-sense", 2, 0, 474 &sirq_polarity_sense_args); 475 if (rc < 0) { 476 dev_dbg(&pdev->dev, 477 "aspeed,sirq-polarity-sense property not found\n"); 478 } else { 479 aspeed_vuart_auto_configure_sirq_polarity( 480 vuart, sirq_polarity_sense_args.np, 481 sirq_polarity_sense_args.args[0], 482 BIT(sirq_polarity_sense_args.args[1])); 483 of_node_put(sirq_polarity_sense_args.np); 484 } 485 486 aspeed_vuart_set_enabled(vuart, true); 487 aspeed_vuart_set_host_tx_discard(vuart, true); 488 platform_set_drvdata(pdev, vuart); 489 490 return 0; 491 492err_clk_disable: 493 clk_disable_unprepare(vuart->clk); 494 irq_dispose_mapping(port.port.irq); 495err_sysfs_remove: 496 sysfs_remove_group(&vuart->dev->kobj, &aspeed_vuart_attr_group); 497 return rc; 498} 499 500static int aspeed_vuart_remove(struct platform_device *pdev) 501{ 502 struct aspeed_vuart *vuart = platform_get_drvdata(pdev); 503 504 del_timer_sync(&vuart->unthrottle_timer); 505 aspeed_vuart_set_enabled(vuart, false); 506 serial8250_unregister_port(vuart->line); 507 sysfs_remove_group(&vuart->dev->kobj, &aspeed_vuart_attr_group); 508 clk_disable_unprepare(vuart->clk); 509 510 return 0; 511} 512 513static const struct of_device_id aspeed_vuart_table[] = { 514 { .compatible = "aspeed,ast2400-vuart" }, 515 { .compatible = "aspeed,ast2500-vuart" }, 516 { }, 517}; 518 519static struct platform_driver aspeed_vuart_driver = { 520 .driver = { 521 .name = "aspeed-vuart", 522 .of_match_table = aspeed_vuart_table, 523 }, 524 .probe = aspeed_vuart_probe, 525 .remove = aspeed_vuart_remove, 526}; 527 528module_platform_driver(aspeed_vuart_driver); 529 530MODULE_AUTHOR("Jeremy Kerr <jk@ozlabs.org>"); 531MODULE_LICENSE("GPL"); 532MODULE_DESCRIPTION("Driver for Aspeed VUART device"); 533