Re: git pull] drm for v4.1-rc1

Alex Deucher
2015-04-24T00:56:05Z

On Thu, Apr 23, 2015 at 5:30 PM, Bjorn Helgaas <bhelgaas@google.com> wrote:
> [+cc Matthew]
>
> On Tue, Apr 21, 2015 at 09:07:45AM -0700, Linus Torvalds wrote:
>> Hmm. The odd Intel PCI resource mess is back.
>>
>> Or maybe it never went away.
>>
>> I get these when suspending. Things *work*, but it's really spamming
>> my logs a fair bit:
>>
>> i915 0000:00:02.0: BAR 6: [??? 0x00000000 flags 0x2] has bogus alignment
>> pci_bus 0000:01: Allocating resources
>> pci_bus 0000:02: Allocating resources
>> i915 0000:00:02.0: BAR 6: [??? 0x00000000 flags 0x2] has bogus alignment
>> i915 0000:00:02.0: BAR 6: [??? 0x00000000 flags 0x2] has bogus alignment
>> i915 0000:00:02.0: BAR 6: [??? 0x00000000 flags 0x2] has bogus alignment
>> i915 0000:00:02.0: BAR 6: [??? 0x00000000 flags 0x2] has bogus alignment
>> i915 0000:00:02.0: BAR 6: [??? 0x00000000 flags 0x2] has bogus alignment
>> i915 0000:00:02.0: BAR 6: [??? 0x00000000 flags 0x2] has bogus alignment
>>
>> That resource is complete garbage. "flags 0x2" is not even a valid
>> flag value. I'm *guessing* it might be IORESOURCE_ROM_SHADOW, but if
>> that is valid, then it should also have have had the IORESOURCE_MEM
>> bit, and it doesn't.
>
> Your i915 does not have a ROM BAR in hardware. If the default video
> device has no ROM BAR, pci_fixup_video() sets IORESOURCE_ROM_SHADOW
> even though the resource flags are zero because the BAR itself doesn't
> exist.
>
> If IORESOURCE_ROM_SHADOW is set, pci_map_rom() assumes there's a
> shadow ROM image at 0xC0000. Is there a shadow image even if the
> device itself doesn't have a ROM BAR?

Very likely yes. With integrated APUs and mobile dGPUs, the vbios
image is often stored as part of the system rom rather than as a
dedicated rom for the GPU. The vbios image is then copied to the
shadow location during sbios init to provide OS access to the rom.

Alex

>
> We could fabricate a resource even if the BAR doesn't exist, e.g.,
> "flags = IORESOURCE_MEM | ... | IORESOURCE_ROM_SHADOW", but that
> would be ugly and error-prone in other places that use the ROM.
>
> Matthew added dev->rom for ROM images supplied by the platform
> (84c1b80e3263 ("PCI: Add support for non-BAR ROMs")). A shadow
> image seems like a similar thing. I think it would be cleaner to get
> rid of IORESOURCE_ROM_SHADOW altogether and instead set "dev->rom =
> 0xC0000" if there's a shadow image, e.g.:
>
> int pcibios_add_device(struct pci_dev *dev)
> {
> if (dev-is-default-vga-device) {
> dev->rom = 0xC0000;
> dev->romlen = 0x20000;
> }
>
> pa_data = boot_params.hdr.setup_data;
> while (pa_data) {
> ...
> if (data->type == SETUP_PCI) {
> rom = (struct pci_setup_rom *)data;
>
> if (dev-is-rom-dev) {
> dev->rom = ...
> dev->romlen = rom->pcilen;
> }
> }
> }
>
> But the rules for figuring out which image to use seem ...
> complicated.
>
> Bjorn
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