arch/powerpc/kernel/legacy_serial.c

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