arch/powerpc/kernel/legacy_serial.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/kernel.h>
   3 #include <linux/serial.h>
   4 #include <linux/serial_8250.h>
   5 #include <linux/serial_core.h>
   6 #include <linux/console.h>
   7 #include <linux/pci.h>
   8 #include <linux/of_address.h>
   9 #include <linux/of_device.h>
  10 #include <linux/serial_reg.h>
  11 #include <asm/io.h>
  12 #include <asm/mmu.h>
  13 #include <asm/prom.h>
  14 #include <asm/serial.h>
  15 #include <asm/udbg.h>
  16 #include <asm/pci-bridge.h>
  17 #include <asm/ppc-pci.h>
  18
  19 #undef DEBUG
  20
  21 #ifdef DEBUG
  22 #define DBG(fmt...) do { printk(fmt); } while(0)
  23 #else
  24 #define DBG(fmt...) do { } while(0)
  25 #endif
  26
  27 #define MAX_LEGACY_SERIAL_PORTS 8
  28
  29 static struct plat_serial8250_port
  30 legacy_serial_ports[MAX_LEGACY_SERIAL_PORTS+1];
  31 static struct legacy_serial_info {
  32         struct device_node              *np;
  33         unsigned int                    speed;
  34         unsigned int                    clock;
  35         int                             irq_check_parent;
  36         phys_addr_t                     taddr;
  37 } legacy_serial_infos[MAX_LEGACY_SERIAL_PORTS];
  38
  39 static const struct of_device_id legacy_serial_parents[] __initconst = {
  40         {.type = "soc",},
  41         {.type = "tsi-bridge",},
  42         {.type = "opb", },
  43         {.compatible = "ibm,opb",},
  44         {.compatible = "simple-bus",},
  45         {.compatible = "wrs,epld-localbus",},
  46         {},
  47 };
  48
  49 static unsigned int legacy_serial_count;
  50 static int legacy_serial_console = -1;
  51
  52 static const upf_t legacy_port_flags = UPF_BOOT_AUTOCONF | UPF_SKIP_TEST |
  53         UPF_SHARE_IRQ | UPF_FIXED_PORT;
  54
  55 static unsigned int tsi_serial_in(struct uart_port *p, int offset)
  56 {
  57         unsigned int tmp;
  58         offset = offset << p->regshift;
  59         if (offset == UART_IIR) {
  60                 tmp = readl(p->membase + (UART_IIR & ~3));
  61                 return (tmp >> 16) & 0xff; /* UART_IIR % 4 == 2 */
  62         } else
  63                 return readb(p->membase + offset);
  64 }
  65
  66 static void tsi_serial_out(struct uart_port *p, int offset, int value)
  67 {
  68         offset = offset << p->regshift;
  69         if (!((offset == UART_IER) && (value & UART_IER_UUE)))
  70                 writeb(value, p->membase + offset);
  71 }
  72
  73 static int __init add_legacy_port(struct device_node *np, int want_index,
  74                                   int iotype, phys_addr_t base,
  75                                   phys_addr_t taddr, unsigned long irq,
  76                                   upf_t flags, int irq_check_parent)
  77 {
  78         const __be32 *clk, *spd, *rs;
  79         u32 clock = BASE_BAUD * 16;
  80         u32 shift = 0;
  81         int index;
  82
  83         /* get clock freq. if present */
  84         clk = of_get_property(np, "clock-frequency", NULL);
  85         if (clk && *clk)
  86                 clock = be32_to_cpup(clk);
  87
  88         /* get default speed if present */
  89         spd = of_get_property(np, "current-speed", NULL);
  90
  91         /* get register shift if present */
  92         rs = of_get_property(np, "reg-shift", NULL);
  93         if (rs && *rs)
  94                 shift = be32_to_cpup(rs);
  95
  96         /* If we have a location index, then try to use it */
  97         if (want_index >= 0 && want_index < MAX_LEGACY_SERIAL_PORTS)
  98                 index = want_index;
  99         else
 100                 index = legacy_serial_count;
 101
 102         /* if our index is still out of range, that mean that
 103          * array is full, we could scan for a free slot but that
 104          * make little sense to bother, just skip the port
 105          */
 106         if (index >= MAX_LEGACY_SERIAL_PORTS)
 107                 return -1;
 108         if (index >= legacy_serial_count)
 109                 legacy_serial_count = index + 1;
 110
 111         /* Check if there is a port who already claimed our slot */
 112         if (legacy_serial_infos[index].np != NULL) {
 113                 /* if we still have some room, move it, else override */
 114                 if (legacy_serial_count < MAX_LEGACY_SERIAL_PORTS) {
 115                         printk(KERN_DEBUG "Moved legacy port %d -> %d\n",
 116                                index, legacy_serial_count);
 117                         legacy_serial_ports[legacy_serial_count] =
 118                                 legacy_serial_ports[index];
 119                         legacy_serial_infos[legacy_serial_count] =
 120                                 legacy_serial_infos[index];
 121                         legacy_serial_count++;
 122                 } else {
 123                         printk(KERN_DEBUG "Replacing legacy port %d\n", index);
 124                 }
 125         }
 126
 127         /* Now fill the entry */
 128         memset(&legacy_serial_ports[index], 0,
 129                sizeof(struct plat_serial8250_port));
 130         if (iotype == UPIO_PORT)
 131                 legacy_serial_ports[index].iobase = base;
 132         else
 133                 legacy_serial_ports[index].mapbase = base;
 134
 135         legacy_serial_ports[index].iotype = iotype;
 136         legacy_serial_ports[index].uartclk = clock;
 137         legacy_serial_ports[index].irq = irq;
 138         legacy_serial_ports[index].flags = flags;
 139         legacy_serial_ports[index].regshift = shift;
 140         legacy_serial_infos[index].taddr = taddr;
 141         legacy_serial_infos[index].np = of_node_get(np);
 142         legacy_serial_infos[index].clock = clock;
 143         legacy_serial_infos[index].speed = spd ? be32_to_cpup(spd) : 0;
 144         legacy_serial_infos[index].irq_check_parent = irq_check_parent;
 145
 146         if (iotype == UPIO_TSI) {
 147                 legacy_serial_ports[index].serial_in = tsi_serial_in;
 148                 legacy_serial_ports[index].serial_out = tsi_serial_out;
 149         }
 150
 151         printk(KERN_DEBUG "Found legacy serial port %d for %pOF\n",
 152                index, np);
 153         printk(KERN_DEBUG "  %s=%llx, taddr=%llx, irq=%lx, clk=%d, speed=%d\n",
 154                (iotype == UPIO_PORT) ? "port" : "mem",
 155                (unsigned long long)base, (unsigned long long)taddr, irq,
 156                legacy_serial_ports[index].uartclk,
 157                legacy_serial_infos[index].speed);
 158
 159         return index;
 160 }
 161
 162 static int __init add_legacy_soc_port(struct device_node *np,
 163                                       struct device_node *soc_dev)
 164 {
 165         u64 addr;
 166         const __be32 *addrp;
 167         struct device_node *tsi = of_get_parent(np);
 168
 169         /* We only support ports that have a clock frequency properly
 170          * encoded in the device-tree.
 171          */
 172         if (of_get_property(np, "clock-frequency", NULL) == NULL)
 173                 return -1;
 174
 175         /* if reg-offset don't try to use it */
 176         if ((of_get_property(np, "reg-offset", NULL) != NULL))
 177                 return -1;
 178
 179         /* if rtas uses this device, don't try to use it as well */
 180         if (of_get_property(np, "used-by-rtas", NULL) != NULL)
 181                 return -1;
 182
 183         /* Get the address */
 184         addrp = of_get_address(soc_dev, 0, NULL, NULL);
 185         if (addrp == NULL)
 186                 return -1;
 187
 188         addr = of_translate_address(soc_dev, addrp);
 189         if (addr == OF_BAD_ADDR)
 190                 return -1;
 191
 192         /* Add port, irq will be dealt with later. We passed a translated
 193          * IO port value. It will be fixed up later along with the irq
 194          */
 195         if (of_node_is_type(tsi, "tsi-bridge"))
 196                 return add_legacy_port(np, -1, UPIO_TSI, addr, addr,
 197                                        0, legacy_port_flags, 0);
 198         else
 199                 return add_legacy_port(np, -1, UPIO_MEM, addr, addr,
 200                                        0, legacy_port_flags, 0);
 201 }
 202
 203 static int __init add_legacy_isa_port(struct device_node *np,
 204                                       struct device_node *isa_brg)
 205 {
 206         const __be32 *reg;
 207         const char *typep;
 208         int index = -1;
 209         u64 taddr;
 210
 211         DBG(" -> add_legacy_isa_port(%pOF)\n", np);
 212
 213         /* Get the ISA port number */
 214         reg = of_get_property(np, "reg", NULL);
 215         if (reg == NULL)
 216                 return -1;
 217
 218         /* Verify it's an IO port, we don't support anything else */
 219         if (!(be32_to_cpu(reg[0]) & 0x00000001))
 220                 return -1;
 221
 222         /* Now look for an "ibm,aix-loc" property that gives us ordering
 223          * if any...
 224          */
 225         typep = of_get_property(np, "ibm,aix-loc", NULL);
 226
 227         /* If we have a location index, then use it */
 228         if (typep && *typep == 'S')
 229                 index = simple_strtol(typep+1, NULL, 0) - 1;
 230
 231         /* Translate ISA address. If it fails, we still register the port
 232          * with no translated address so that it can be picked up as an IO
 233          * port later by the serial driver
 234          *
 235          * Note: Don't even try on P8 lpc, we know it's not directly mapped
 236          */
 237         if (!of_device_is_compatible(isa_brg, "ibm,power8-lpc") ||
 238             of_get_property(isa_brg, "ranges", NULL)) {
 239                 taddr = of_translate_address(np, reg);
 240                 if (taddr == OF_BAD_ADDR)
 241                         taddr = 0;
 242         } else
 243                 taddr = 0;
 244
 245         /* Add port, irq will be dealt with later */
 246         return add_legacy_port(np, index, UPIO_PORT, be32_to_cpu(reg[1]),
 247                                taddr, 0, legacy_port_flags, 0);
 248
 249 }
 250
 251 #ifdef CONFIG_PCI
 252 static int __init add_legacy_pci_port(struct device_node *np,
 253                                       struct device_node *pci_dev)
 254 {
 255         u64 addr, base;
 256         const __be32 *addrp;
 257         unsigned int flags;
 258         int iotype, index = -1, lindex = 0;
 259
 260         DBG(" -> add_legacy_pci_port(%pOF)\n", np);
 261
 262         /* We only support ports that have a clock frequency properly
 263          * encoded in the device-tree (that is have an fcode). Anything
 264          * else can't be used that early and will be normally probed by
 265          * the generic 8250_pci driver later on. The reason is that 8250
 266          * compatible UARTs on PCI need all sort of quirks (port offsets
 267          * etc...) that this code doesn't know about
 268          */
 269         if (of_get_property(np, "clock-frequency", NULL) == NULL)
 270                 return -1;
 271
 272         /* Get the PCI address. Assume BAR 0 */
 273         addrp = of_get_pci_address(pci_dev, 0, NULL, &flags);
 274         if (addrp == NULL)
 275                 return -1;
 276
 277         /* We only support BAR 0 for now */
 278         iotype = (flags & IORESOURCE_MEM) ? UPIO_MEM : UPIO_PORT;
 279         addr = of_translate_address(pci_dev, addrp);
 280         if (addr == OF_BAD_ADDR)
 281                 return -1;
 282
 283         /* Set the IO base to the same as the translated address for MMIO,
 284          * or to the domain local IO base for PIO (it will be fixed up later)
 285          */
 286         if (iotype == UPIO_MEM)
 287                 base = addr;
 288         else
 289                 base = of_read_number(&addrp[2], 1);
 290
 291         /* Try to guess an index... If we have subdevices of the pci dev,
 292          * we get to their "reg" property
 293          */
 294         if (np != pci_dev) {
 295                 const __be32 *reg = of_get_property(np, "reg", NULL);
 296                 if (reg && (be32_to_cpup(reg) < 4))
 297                         index = lindex = be32_to_cpup(reg);
 298         }
 299
 300         /* Local index means it's the Nth port in the PCI chip. Unfortunately
 301          * the offset to add here is device specific. We know about those
 302          * EXAR ports and we default to the most common case. If your UART
 303          * doesn't work for these settings, you'll have to add your own special
 304          * cases here
 305          */
 306         if (of_device_is_compatible(pci_dev, "pci13a8,152") ||
 307             of_device_is_compatible(pci_dev, "pci13a8,154") ||
 308             of_device_is_compatible(pci_dev, "pci13a8,158")) {
 309                 addr += 0x200 * lindex;
 310                 base += 0x200 * lindex;
 311         } else {
 312                 addr += 8 * lindex;
 313                 base += 8 * lindex;
 314         }
 315
 316         /* Add port, irq will be dealt with later. We passed a translated
 317          * IO port value. It will be fixed up later along with the irq
 318          */
 319         return add_legacy_port(np, index, iotype, base, addr, 0,
 320                                legacy_port_flags, np != pci_dev);
 321 }
 322 #endif
 323
 324 static void __init setup_legacy_serial_console(int console)
 325 {
 326         struct legacy_serial_info *info = &legacy_serial_infos[console];
 327         struct plat_serial8250_port *port = &legacy_serial_ports[console];
 328         void __iomem *addr;
 329         unsigned int stride;
 330
 331         stride = 1 << port->regshift;
 332
 333         /* Check if a translated MMIO address has been found */
 334         if (info->taddr) {
 335                 addr = ioremap(info->taddr, 0x1000);
 336                 if (addr == NULL)
 337                         return;
 338                 udbg_uart_init_mmio(addr, stride);
 339         } else {
 340                 /* Check if it's PIO and we support untranslated PIO */
 341                 if (port->iotype == UPIO_PORT && isa_io_special)
 342                         udbg_uart_init_pio(port->iobase, stride);
 343                 else
 344                         return;
 345         }
 346
 347         /* Try to query the current speed */
 348         if (info->speed == 0)
 349                 info->speed = udbg_probe_uart_speed(info->clock);
 350
 351         /* Set it up */
 352         DBG("default console speed = %d\n", info->speed);
 353         udbg_uart_setup(info->speed, info->clock);
 354 }
 355
 356 /*
 357  * This is called very early, as part of setup_system() or eventually
 358  * setup_arch(), basically before anything else in this file. This function
 359  * will try to build a list of all the available 8250-compatible serial ports
 360  * in the machine using the Open Firmware device-tree. It currently only deals
 361  * with ISA and PCI busses but could be extended. It allows a very early boot
 362  * console to be initialized, that list is also used later to provide 8250 with
 363  * the machine non-PCI ports and to properly pick the default console port
 364  */
 365 void __init find_legacy_serial_ports(void)
 366 {
 367         struct device_node *np, *stdout = NULL;
 368         const char *path;
 369         int index;
 370
 371         DBG(" -> find_legacy_serial_port()\n");
 372
 373         /* Now find out if one of these is out firmware console */
 374         path = of_get_property(of_chosen, "linux,stdout-path", NULL);
 375         if (path == NULL)
 376                 path = of_get_property(of_chosen, "stdout-path", NULL);
 377         if (path != NULL) {
 378                 stdout = of_find_node_by_path(path);
 379                 if (stdout)
 380                         DBG("stdout is %pOF\n", stdout);
 381         } else {
 382                 DBG(" no linux,stdout-path !\n");
 383         }
 384
 385         /* Iterate over all the 16550 ports, looking for known parents */
 386         for_each_compatible_node(np, "serial", "ns16550") {
 387                 struct device_node *parent = of_get_parent(np);
 388                 if (!parent)
 389                         continue;
 390                 if (of_match_node(legacy_serial_parents, parent) != NULL) {
 391                         if (of_device_is_available(np)) {
 392                                 index = add_legacy_soc_port(np, np);
 393                                 if (index >= 0 && np == stdout)
 394                                         legacy_serial_console = index;
 395                         }
 396                 }
 397                 of_node_put(parent);
 398         }
 399
 400         /* Next, fill our array with ISA ports */
 401         for_each_node_by_type(np, "serial") {
 402                 struct device_node *isa = of_get_parent(np);
 403                 if (of_node_name_eq(isa, "isa") || of_node_name_eq(isa, "lpc")) {
 404                         if (of_device_is_available(np)) {
 405                                 index = add_legacy_isa_port(np, isa);
 406                                 if (index >= 0 && np == stdout)
 407                                         legacy_serial_console = index;
 408                         }
 409                 }
 410                 of_node_put(isa);
 411         }
 412
 413 #ifdef CONFIG_PCI
 414         /* Next, try to locate PCI ports */
 415         for (np = NULL; (np = of_find_all_nodes(np));) {
 416                 struct device_node *pci, *parent = of_get_parent(np);
 417                 if (of_node_name_eq(parent, "isa")) {
 418                         of_node_put(parent);
 419                         continue;
 420                 }
 421                 if (!of_node_name_eq(np, "serial") &&
 422                     !of_node_is_type(np, "serial")) {
 423                         of_node_put(parent);
 424                         continue;
 425                 }
 426                 /* Check for known pciclass, and also check whether we have
 427                  * a device with child nodes for ports or not
 428                  */
 429                 if (of_device_is_compatible(np, "pciclass,0700") ||
 430                     of_device_is_compatible(np, "pciclass,070002"))
 431                         pci = np;
 432                 else if (of_device_is_compatible(parent, "pciclass,0700") ||
 433                          of_device_is_compatible(parent, "pciclass,070002"))
 434                         pci = parent;
 435                 else {
 436                         of_node_put(parent);
 437                         continue;
 438                 }
 439                 index = add_legacy_pci_port(np, pci);
 440                 if (index >= 0 && np == stdout)
 441                         legacy_serial_console = index;
 442                 of_node_put(parent);
 443         }
 444 #endif
 445
 446         DBG("legacy_serial_console = %d\n", legacy_serial_console);
 447         if (legacy_serial_console >= 0)
 448                 setup_legacy_serial_console(legacy_serial_console);
 449         DBG(" <- find_legacy_serial_port()\n");
 450 }
 451
 452 static struct platform_device serial_device = {
 453         .name   = "serial8250",
 454         .id     = PLAT8250_DEV_PLATFORM,
 455         .dev    = {
 456                 .platform_data = legacy_serial_ports,
 457         },
 458 };
 459
 460 static void __init fixup_port_irq(int index,
 461                                   struct device_node *np,
 462                                   struct plat_serial8250_port *port)
 463 {
 464         unsigned int virq;
 465
 466         DBG("fixup_port_irq(%d)\n", index);
 467
 468         virq = irq_of_parse_and_map(np, 0);
 469         if (!virq && legacy_serial_infos[index].irq_check_parent) {
 470                 np = of_get_parent(np);
 471                 if (np == NULL)
 472                         return;
 473                 virq = irq_of_parse_and_map(np, 0);
 474                 of_node_put(np);
 475         }
 476         if (!virq)
 477                 return;
 478
 479         port->irq = virq;
 480
 481 #ifdef CONFIG_SERIAL_8250_FSL
 482         if (of_device_is_compatible(np, "fsl,ns16550")) {
 483                 port->handle_irq = fsl8250_handle_irq;
 484                 port->has_sysrq = IS_ENABLED(CONFIG_SERIAL_8250_CONSOLE);
 485         }
 486 #endif
 487 }
 488
 489 static void __init fixup_port_pio(int index,
 490                                   struct device_node *np,
 491                                   struct plat_serial8250_port *port)
 492 {
 493 #ifdef CONFIG_PCI
 494         struct pci_controller *hose;
 495
 496         DBG("fixup_port_pio(%d)\n", index);
 497
 498         hose = pci_find_hose_for_OF_device(np);
 499         if (hose) {
 500                 unsigned long offset = (unsigned long)hose->io_base_virt -
 501 #ifdef CONFIG_PPC64
 502                         pci_io_base;
 503 #else
 504                         isa_io_base;
 505 #endif
 506                 DBG("port %d, IO %lx -> %lx\n",
 507                     index, port->iobase, port->iobase + offset);
 508                 port->iobase += offset;
 509         }
 510 #endif
 511 }
 512
 513 static void __init fixup_port_mmio(int index,
 514                                    struct device_node *np,
 515                                    struct plat_serial8250_port *port)
 516 {
 517         DBG("fixup_port_mmio(%d)\n", index);
 518
 519         port->membase = ioremap(port->mapbase, 0x100);
 520 }
 521
 522 /*
 523  * This is called as an arch initcall, hopefully before the PCI bus is
 524  * probed and/or the 8250 driver loaded since we need to register our
 525  * platform devices before 8250 PCI ones are detected as some of them
 526  * must properly "override" the platform ones.
 527  *
 528  * This function fixes up the interrupt value for platform ports as it
 529  * couldn't be done earlier before interrupt maps have been parsed. It
 530  * also "corrects" the IO address for PIO ports for the same reason,
 531  * since earlier, the PHBs virtual IO space wasn't assigned yet. It then
 532  * registers all those platform ports for use by the 8250 driver when it
 533  * finally loads.
 534  */
 535 static int __init serial_dev_init(void)
 536 {
 537         int i;
 538
 539         if (legacy_serial_count == 0)
 540                 return -ENODEV;
 541
 542         /*
 543          * Before we register the platform serial devices, we need
 544          * to fixup their interrupts and their IO ports.
 545          */
 546         DBG("Fixing serial ports interrupts and IO ports ...\n");
 547
 548         for (i = 0; i < legacy_serial_count; i++) {
 549                 struct plat_serial8250_port *port = &legacy_serial_ports[i];
 550                 struct device_node *np = legacy_serial_infos[i].np;
 551
 552                 if (!port->irq)
 553                         fixup_port_irq(i, np, port);
 554                 if (port->iotype == UPIO_PORT)
 555                         fixup_port_pio(i, np, port);
 556                 if ((port->iotype == UPIO_MEM) || (port->iotype == UPIO_TSI))
 557                         fixup_port_mmio(i, np, port);
 558         }
 559
 560         DBG("Registering platform serial ports\n");
 561
 562         return platform_device_register(&serial_device);
 563 }
 564 device_initcall(serial_dev_init);
 565
 566
 567 #ifdef CONFIG_SERIAL_8250_CONSOLE
 568 /*
 569  * This is called very early, as part of console_init() (typically just after
 570  * time_init()). This function is respondible for trying to find a good
 571  * default console on serial ports. It tries to match the open firmware
 572  * default output with one of the available serial console drivers that have
 573  * been probed earlier by find_legacy_serial_ports()
 574  */
 575 static int __init check_legacy_serial_console(void)
 576 {
 577         struct device_node *prom_stdout = NULL;
 578         int i, speed = 0, offset = 0;
 579         const char *name;
 580         const __be32 *spd;
 581
 582         DBG(" -> check_legacy_serial_console()\n");
 583
 584         /* The user has requested a console so this is already set up. */
 585         if (strstr(boot_command_line, "console=")) {
 586                 DBG(" console was specified !\n");
 587                 return -EBUSY;
 588         }
 589
 590         if (!of_chosen) {
 591                 DBG(" of_chosen is NULL !\n");
 592                 return -ENODEV;
 593         }
 594
 595         if (legacy_serial_console < 0) {
 596                 DBG(" legacy_serial_console not found !\n");
 597                 return -ENODEV;
 598         }
 599         /* We are getting a weird phandle from OF ... */
 600         /* ... So use the full path instead */
 601         name = of_get_property(of_chosen, "linux,stdout-path", NULL);
 602         if (name == NULL)
 603                 name = of_get_property(of_chosen, "stdout-path", NULL);
 604         if (name == NULL) {
 605                 DBG(" no stdout-path !\n");
 606                 return -ENODEV;
 607         }
 608         prom_stdout = of_find_node_by_path(name);
 609         if (!prom_stdout) {
 610                 DBG(" can't find stdout package %s !\n", name);
 611                 return -ENODEV;
 612         }
 613         DBG("stdout is %pOF\n", prom_stdout);
 614
 615         name = of_get_property(prom_stdout, "name", NULL);
 616         if (!name) {
 617                 DBG(" stdout package has no name !\n");
 618                 goto not_found;
 619         }
 620         spd = of_get_property(prom_stdout, "current-speed", NULL);
 621         if (spd)
 622                 speed = be32_to_cpup(spd);
 623
 624         if (strcmp(name, "serial") != 0)
 625                 goto not_found;
 626
 627         /* Look for it in probed array */
 628         for (i = 0; i < legacy_serial_count; i++) {
 629                 if (prom_stdout != legacy_serial_infos[i].np)
 630                         continue;
 631                 offset = i;
 632                 speed = legacy_serial_infos[i].speed;
 633                 break;
 634         }
 635         if (i >= legacy_serial_count)
 636                 goto not_found;
 637
 638         of_node_put(prom_stdout);
 639
 640         DBG("Found serial console at ttyS%d\n", offset);
 641
 642         if (speed) {
 643                 static char __initdata opt[16];
 644                 sprintf(opt, "%d", speed);
 645                 return add_preferred_console("ttyS", offset, opt);
 646         } else
 647                 return add_preferred_console("ttyS", offset, NULL);
 648
 649  not_found:
 650         DBG("No preferred console found !\n");
 651         of_node_put(prom_stdout);
 652         return -ENODEV;
 653 }
 654 console_initcall(check_legacy_serial_console);
 655
 656 #endif /* CONFIG_SERIAL_8250_CONSOLE */