Bug 36462

Summary: kernel doesn't reserve PNP resources, causes hang
Product: Drivers Reporter: Bjorn Helgaas (bjorn)
Component: PNPAssignee: Adam Belay (ambx1)
Status: NEW ---    
Severity: normal CC: xerofoify
Priority: P1    
Hardware: All   
OS: Linux   
URL: https://lkml.org/lkml/2011/5/17/54
Kernel Version: 2.6.30 Subsystem:
Regression: No Bisected commit-id:

Description Bjorn Helgaas 2011-06-01 16:33:08 UTC 
See the email thread at https://lkml.org/lkml/2011/5/17/54

Michael has a system with several UARTs at [io 0x1900-0x1947].  Even when these are correctly described as PNP0500 devices in the ACPI namespace, Linux assigns the [io 0x1000-0x1fff] range to a P2P bridge window.  This should not happen, because the ACPI description should be enough to tell us that the 0x1900-0x1947 range is already in use.

This causes a hang on Michael's system.  The workaround for now is for Michael to describe the [io 0x1900-0x1947] range as a PNP0C02 device, because we handle those motherboard devices specially -- we do reserve their resources before we try to assign PCI resources.  But this is a hack and prevents the 8250 driver from claiming the UARTs as it should.
Comment 1 xerofoify 2014-06-25 16:00:32 UTC 
This bug is old. Please test against a newer kernel verison.
Thanks Nick