Hello,
we've gotten a customer report of a problem whereby our framebuffer is not visible through the kernel. the kernel data structures in struct pci_dev have bar1 (our framebuffer) set to 0, and the bar does not appear in /proc/pci.
after a little investigation, it appears that the bios allocated a 64-bit bar in pci config space. our gpu claims 64-bit support in pci config space and the cpu is an em64t. but the customer is running a 32-bit kernel on the em64t, which is a reasonable thing to do. it turns out the pci driver does not like 64-bit bars on a 32-bit kernel and prints out the following messages during boot:
PCI: PCI BIOS revision 2.10 entry at 0xf0031, last bus=5 PCI: Using configuration type 1 PCI: Probing PCI hardware PCI: Probing PCI hardware (bus 00) PCI: Ignoring BAR0-3 of IDE controller 00:1f.1 PCI: Unable to handle 64-bit address space for PCI: Unable to handle 64-bit address space for PCI: Unable to handle 64-bit address for device 03:00.0 PCI: Unable to handle 64-bit address space for
Is this an expected problem? Is there any reason why the 32-bit kernel couldn't handle 64-bit bars?
hmmm, that's a good question.
I wonder if ioremap() even supports 64-bit addresses on 32-bit platforms?
64-bit MMIO is a bit different from 64-bit DMA; though its still only page tables...
Jeff
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