Re: [PATCH 1/2] PCI: leave MEM and IO decoding disabled during 64-bit BAR sizing, too

Hi,

On Thu, Aug 23, 2012 at 11:02 AM, Bjorn Helgaas [off-list ref] wrote:

On Thu, Aug 23, 2012 at 12:28:23AM -0700, Olof Johansson wrote:

quoted

Hi,

On Mon, Jul 9, 2012 at 11:20 AM, Bjorn Helgaas [off-list ref] wrote:

quoted

After 253d2e5498, we disable MEM and IO decoding for most devices while we
size 32-bit BARs.  However, we restore the original COMMAND register before
we size the upper 32 bits of 64-bit BARs, so we can still cause a conflict.

This patch waits to restore the original COMMAND register until we're
completely finished sizing the BAR.

Reference: https://lkml.org/lkml/2007/8/25/154
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

This patch causes boot lockup on PA Semi hardware, since it disables
the bar on the UART that is used for console, and it has printks
between the old and the new re-enable location. If I boot with 'debug'
level for printk, I hit this. If I boot with just regular console
args, I don't.

I'm guessing any other platform that uses MMIO-based UART on PCI for
console will have similar issues. I can verify on Chrome OS x86
hardware tomorrow if legacy powerpc isn't important enough to care
about. :-)

I have no proposal for a fix for this. Can you please consider
reverting for 3.6 unless someone has a better idea?

Thanks a lot for finding and debugging this!

Can you try the patch below?


commit cfc29ece86d648e63fb46de81b2bf8e3e107672c
Author: Bjorn Helgaas [off-list ref]
Date:   Thu Aug 23 10:53:08 2012 -0600

    PCI: Don't print anything while decoding is disabled

    If we try to print to the console device while its decoding is disabled,
    the system will hang.

    Reported-by: Olof Johansson [off-list ref]
    Signed-off-by: Bjorn Helgaas [off-list ref]

Ah yes, of course. Teaches me to try to do anything productive late at
night. Tested fine here.

Acked-by: Olof Johansson <redacted>


Thanks!

-Olof