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    SubjectRe: Kernel > 2.6.30: PCI issue causes Kernel freeze at booting
    On Wed, May 18, 2011 at 1:44 AM, Hornung, Michael <mhornung@init-ka.de> wrote:
    >>> There is an UART (FPGA IP Core) in that system located at address 1900h using interrupt 3. In order to get Kernel messages at boot time,
    >>> I changed file arch/x86/include/asm/serial.h as follows:
    >>>
    >>> -        { 0, BASE_BAUD, 0x3F8, 4, STD_COM_FLAGS },      /* ttyS0 */     \
    >>> +        { 0, BASE_BAUD, 0x1900, 3, STD_COM_FLAGS },     /* ttyS0 */    \
    >>>
    >>> that is the only change I made to the kernel sources.
    >
    >> Is this UART connected via PCI?  I don't think so, because I don't see
    >> any I/O BARs that include 0x1900.
    >
    > The UART is connected via LPC bus.

    Makes sense; that's a common way for attaching UARTs, and they are
    normally described via ACPI. When you do that, I think it will show
    up as ttyS4 (be sure you build with CONFIG_SERIAL_8250_PNP=y), so
    you'll have to use "console=ttyS4" when you boot. ttyS0-ttyS3 are
    taken by the hard-coded ports in serial.h, even though they may not
    exist on your platform.

    Bjorn
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