PNPACPI probes serial twice, messes up serial console

[Keith Owens]

Dell SC1425 x86_64 running in i386 mode (the problem also occurs in
x86_64 mode).  Kernel 2.6.21-rc4, gcc 4.1.0.  Config extract at end.

Booting with 'console=tty console=ttyS0,9600'.  The serial console on
ttyS0 (0x3f8, irq 4) is probed twice, once from serial8250_init() and
again from serial_pnp_probe().  The serial console output is correct
until the second probe (from PNP) gets to these lines in
serial8250_config_port()

	if (flags & UART_CONFIG_TYPE)
		autoconfig(up, probeflags);

After the call to autoconfig(), the serial console starts printing NUL
characters instead of the console output.  The number of NUL characters
corresponds closely with the number of characters written to the VT
console, IOW it outputs each serial character as NUL instead of the
correct character.  When the kernel boots /sbin/init, the console
resets to printing normal characters.

AFAICT, the second probe of the UART is doing something nasty to the
hardware.  This is not a recent problem, I can reproduce the problem on
2.6.16.  Booting with pnpacpi=off removes the problem, but that
supresses all the PNPACPI code, not just the second probe of the serial
devices.

Should pnpacpi probe and setup the serial devices even when thay have
already been setup?  Or this is something strange about the UART in
this particular box?

FWIW, the serial console is plugged into a serial to USB converter
(pl2303), my laptop has no serial ports.  That should not make a
difference, but just in case it does ...

Config extract:

X86_32=y
GENERIC_TIME=y
CLOCKSOURCE_WATCHDOG=y
GENERIC_CLOCKEVENTS=y
GENERIC_CLOCKEVENTS_BROADCAST=y
LOCKDEP_SUPPORT=y
STACKTRACE_SUPPORT=y
SEMAPHORE_SLEEPERS=y
X86=y
MMU=y
ZONE_DMA=y
GENERIC_ISA_DMA=y
GENERIC_IOMAP=y
GENERIC_BUG=y
GENERIC_HWEIGHT=y
ARCH_MAY_HAVE_PC_FDC=y
DMI=y
DEFCONFIG_LIST="/lib/modules/$UNAME_RELEASE/.config"
EXPERIMENTAL=y
LOCK_KERNEL=y
INIT_ENV_ARG_LIMIT=32
LOCALVERSION="-i386-kaos"
LOCALVERSION_AUTO=y
SWAP=y
SYSVIPC=y
SYSVIPC_SYSCTL=y
POSIX_MQUEUE=y
IKCONFIG=y
IKCONFIG_PROC=y
SYSFS_DEPRECATED=y
CC_OPTIMIZE_FOR_SIZE=y
SYSCTL=y
EMBEDDED=y
SYSCTL_SYSCALL=y
KALLSYMS=y
KALLSYMS_ALL=y
HOTPLUG=y
PRINTK=y
BUG=y
ELF_CORE=y
BASE_FULL=y
FUTEX=y
EPOLL=y
SHMEM=y
SLAB=y
VM_EVENT_COUNTERS=y
RT_MUTEXES=y
BASE_SMALL=0
MODULES=y
MODULE_UNLOAD=y
KMOD=y
STOP_MACHINE=y
BLOCK=y
LBD=y
LSF=y
IOSCHED_NOOP=y
IOSCHED_AS=y
IOSCHED_DEADLINE=y
IOSCHED_CFQ=y
DEFAULT_DEADLINE=y
DEFAULT_IOSCHED="deadline"
TICK_ONESHOT=y
HIGH_RES_TIMERS=y
SMP=y
X86_PC=y
MPENTIUM4=y
X86_CMPXCHG=y
X86_L1_CACHE_SHIFT=7
RWSEM_XCHGADD_ALGORITHM=y
GENERIC_CALIBRATE_DELAY=y
X86_WP_WORKS_OK=y
X86_INVLPG=y
X86_BSWAP=y
X86_POPAD_OK=y
X86_CMPXCHG64=y
X86_GOOD_APIC=y
X86_INTEL_USERCOPY=y
X86_USE_PPRO_CHECKSUM=y
X86_TSC=y
HPET_TIMER=y
HPET_EMULATE_RTC=y
NR_CPUS=8
SCHED_SMT=y
PREEMPT_NONE=y
X86_LOCAL_APIC=y
X86_IO_APIC=y
X86_MCE=y
X86_MCE_NONFATAL=y
X86_MCE_P4THERMAL=y
MICROCODE=m
MICROCODE_OLD_INTERFACE=y
X86_MSR=m
X86_CPUID=m
HIGHMEM4G=y
VMSPLIT_3G=y
PAGE_OFFSET=0xC0000000
HIGHMEM=y
ARCH_FLATMEM_ENABLE=y
ARCH_SPARSEMEM_ENABLE=y
ARCH_SELECT_MEMORY_MODEL=y
ARCH_POPULATES_NODE_MAP=y
SELECT_MEMORY_MODEL=y
FLATMEM_MANUAL=y
FLATMEM=y
FLAT_NODE_MEM_MAP=y
SPARSEMEM_STATIC=y
SPLIT_PTLOCK_CPUS=4
ZONE_DMA_FLAG=1
MTRR=y
IRQBALANCE=y
HZ_250=y
HZ=250
PHYSICAL_START=0x100000
PHYSICAL_ALIGN=0x100000
COMPAT_VDSO=y
ARCH_ENABLE_MEMORY_HOTPLUG=y
PM=y
ACPI=y
ACPI_PROCFS=y
ACPI_BUTTON=m
ACPI_FAN=m
ACPI_PROCESSOR=m
ACPI_BLACKLIST_YEAR=0
ACPI_EC=y
ACPI_POWER=y
ACPI_SYSTEM=y
PCI=y
PCI_GOANY=y
PCI_BIOS=y
PCI_DIRECT=y
PCI_MMCONFIG=y
PCIEPORTBUS=y
PCIEAER=y
PCI_MSI=y
HT_IRQ=y
ISA_DMA_API=y
BINFMT_ELF=y
BINFMT_MISC=m
NET=y
PACKET=y
PACKET_MMAP=y
UNIX=y
XFRM=y
INET=y
IP_MULTICAST=y
IP_ADVANCED_ROUTER=y
ASK_IP_FIB_HASH=y
IP_FIB_HASH=y
IP_ROUTE_MULTIPATH=y
IP_ROUTE_VERBOSE=y
SYN_COOKIES=y
INET_XFRM_MODE_BEET=y
INET_DIAG=y
INET_TCP_DIAG=y
TCP_CONG_CUBIC=y
DEFAULT_TCP_CONG="cubic"
NETFILTER=y
NETFILTER_NETLINK=m
NETFILTER_NETLINK_LOG=m
NETFILTER_XTABLES=y
NETFILTER_XT_TARGET_CLASSIFY=m
NETFILTER_XT_TARGET_MARK=m
NETFILTER_XT_MATCH_COMMENT=m
NETFILTER_XT_MATCH_DCCP=m
NETFILTER_XT_MATCH_ESP=m
NETFILTER_XT_MATCH_LENGTH=m
NETFILTER_XT_MATCH_LIMIT=m
NETFILTER_XT_MATCH_MAC=m
NETFILTER_XT_MATCH_MARK=m
NETFILTER_XT_MATCH_MULTIPORT=m
NETFILTER_XT_MATCH_PKTTYPE=m
NETFILTER_XT_MATCH_QUOTA=m
NETFILTER_XT_MATCH_REALM=m
NETFILTER_XT_MATCH_SCTP=m
NETFILTER_XT_MATCH_STATISTIC=m
NETFILTER_XT_MATCH_TCPMSS=m
IP_NF_IPTABLES=y
IP_NF_MATCH_IPRANGE=m
IP_NF_MATCH_TOS=m
IP_NF_MATCH_RECENT=m
IP_NF_MATCH_ECN=m
IP_NF_MATCH_AH=m
IP_NF_MATCH_TTL=m
IP_NF_MATCH_OWNER=m
IP_NF_MATCH_ADDRTYPE=m
IP_NF_FILTER=y
IP_NF_TARGET_REJECT=y
IP_NF_TARGET_ULOG=y
VLAN_8021Q=y
NET_CLS_ROUTE=y
STANDALONE=y
PREVENT_FIRMWARE_BUILD=y
FW_LOADER=m
CONNECTOR=m
PNP=y
PNP_DEBUG=y
PNPACPI=y
BLK_DEV_FD=m
BLK_DEV_LOOP=m
IDE=m
IDE_MAX_HWIFS=4
BLK_DEV_IDE=m
BLK_DEV_IDEDISK=m
IDEDISK_MULTI_MODE=y
BLK_DEV_IDECD=m
IDE_TASK_IOCTL=y
BLK_DEV_IDEPCI=y
IDEPCI_SHARE_IRQ=y
BLK_DEV_IDEDMA_PCI=y
IDEDMA_PCI_AUTO=y
BLK_DEV_PIIX=m
BLK_DEV_IDEDMA=y
IDEDMA_AUTO=y
RAID_ATTRS=m
SCSI=y
SCSI_PROC_FS=y
BLK_DEV_SD=y
CHR_DEV_SG=y
SCSI_CONSTANTS=y
SCSI_SPI_ATTRS=y
SCSI_3W_9XXX=y
SCSI_SYM53C8XX_2=y
SCSI_SYM53C8XX_DMA_ADDRESSING_MODE=1
SCSI_SYM53C8XX_DEFAULT_TAGS=16
SCSI_SYM53C8XX_MAX_TAGS=64
SCSI_SYM53C8XX_MMIO=y
ATA=y
ATA_PIIX=y
SATA_ACPI=y
MD=y
BLK_DEV_MD=y
MD_RAID1=y
BLK_DEV_DM=y
DM_SNAPSHOT=y
DM_MIRROR=y
NETDEVICES=y
DUMMY=m
BONDING=m
E1000=y
E1000_NAPI=y
SKY2=m
NETCONSOLE=m
NETPOLL=y
NET_POLL_CONTROLLER=y
INPUT=y
INPUT_KEYBOARD=y
KEYBOARD_ATKBD=y
SERIO=y
SERIO_I8042=y
SERIO_LIBPS2=y
SERIO_RAW=m
VT=y
VT_CONSOLE=y
HW_CONSOLE=y
SERIAL_8250=y
SERIAL_8250_CONSOLE=y
SERIAL_8250_PCI=m
SERIAL_8250_PNP=y
SERIAL_8250_NR_UARTS=4
SERIAL_8250_RUNTIME_UARTS=4
SERIAL_CORE=y
SERIAL_CORE_CONSOLE=y
UNIX98_PTYS=y
IPMI_HANDLER=y
IPMI_PANIC_EVENT=y
IPMI_DEVICE_INTERFACE=y
IPMI_SI=y
IPMI_WATCHDOG=y
IPMI_POWEROFF=m
WATCHDOG=y
SOFT_WATCHDOG=m
I8XX_TCO=y
NVRAM=m
RTC=y
HPET=y
HPET_MMAP=y
I2C=y
I2C_CHARDEV=m
I2C_ALGOBIT=m
I2C_I801=y
SENSORS_EEPROM=m
HWMON=y
VGA_CONSOLE=y
DUMMY_CONSOLE=y
HID=y
USB_ARCH_HAS_HCD=y
USB_ARCH_HAS_OHCI=y
USB_ARCH_HAS_EHCI=y
USB=y
USB_DEVICEFS=y
USB_EHCI_HCD=y
USB_STORAGE=m
USB_HID=y
USB_MON=y
USB_SERIAL=m
USB_SERIAL_GENERIC=y
USB_SERIAL_PL2303=m
EDAC=y
EDAC_MM_EDAC=y
EDAC_E752X=y
EDAC_POLL=y
EXT2_FS=m
EXT3_FS=y
JBD=y
XFS_FS=y
INOTIFY=y
INOTIFY_USER=y
ISO9660_FS=m
JOLIET=y
UDF_FS=m
UDF_NLS=y
FAT_FS=m
MSDOS_FS=m
VFAT_FS=m
FAT_DEFAULT_CODEPAGE=850
FAT_DEFAULT_IOCHARSET="iso8859-1"
PROC_FS=y
PROC_KCORE=y
PROC_SYSCTL=y
SYSFS=y
TMPFS=y
RAMFS=y
NFS_FS=y
NFS_V3=y
NFSD=y
NFSD_V3=y
LOCKD=y
LOCKD_V4=y
EXPORTFS=y
NFS_COMMON=y
SUNRPC=y
MSDOS_PARTITION=y
NLS=m
NLS_DEFAULT="iso8859-15"
NLS_CODEPAGE_437=m
NLS_CODEPAGE_850=m
NLS_CODEPAGE_865=m
NLS_ASCII=m
NLS_ISO8859_1=m
NLS_ISO8859_15=m
NLS_UTF8=m
TRACE_IRQFLAGS_SUPPORT=y
ENABLE_MUST_CHECK=y
MAGIC_SYSRQ=y
DEBUG_KERNEL=y
LOG_BUF_SHIFT=16
DETECT_SOFTLOCKUP=y
DEBUG_SPINLOCK=y
DEBUG_MUTEXES=y
DEBUG_BUGVERBOSE=y
FORCED_INLINING=y
DEBUG_STACKOVERFLOW=y
DEBUG_RODATA=y
X86_FIND_SMP_CONFIG=y
X86_MPPARSE=y
DOUBLEFAULT=y
KDB=y
KDB_MODULES=y
KDB_CONTINUE_CATASTROPHIC=0
BITREVERSE=y
CRC32=y
PLIST=y
HAS_IOMEM=y
HAS_IOPORT=y
GENERIC_HARDIRQS=y
GENERIC_IRQ_PROBE=y
GENERIC_PENDING_IRQ=y
X86_SMP=y
X86_HT=y
X86_BIOS_REBOOT=y
X86_TRAMPOLINE=y
KTIME_SCALAR=y

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