Re: Kernel > 2.6.30: PCI issue causes Kernel freeze at booting

From: Bjorn Helgaas
Date: Mon May 23 2011 - 12:30:45 EST

On Wed, May 18, 2011 at 7:56 AM, Bjorn Helgaas <bhelgaas@xxxxxxxxxx> wrote:
> On Wed, May 18, 2011 at 1:44 AM, Hornung, Michael <mhornung@xxxxxxxxxx> 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.

Hi Michael,

Any update on this problem? Did it make any difference to put the
UART in the ACPI namespace?

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