[Nouveau] Resource map sanity check fails after GRUB "keeps" the gfx mode

[Pavel Roskin]

On Fri, 4 Oct 2013 01:08:34 +0200
David Herrmann <dh.herrmann at gmail.com> wrote:

> > CONFIG_X86_SYSFB is always defined.  I doubt an x86 kernel would
> > compile without it.  create_simplefb() is used in
> > arch/x86/kernel/sysfb.c that is compiled unconditionally and that
> > function is defined in arch/x86/kernel/sysfb_simplefb.c that is only
> > compiled if CONFIG_X86_SYSFB is defined.
> 
> You can set CONFIG_X86_SYSFB=n and everything works fine. It's the
> default and is what pre-3.12 kernels always did.

Of course, you are right, I missed sysfb.h.

> > I tried four combinations: with and without IORESOURCE_BUSY and with
> > and without the PCI resource adjustment.  The only combination when
> > nvidiafb probes the hardware is when IORESOURCE_BUSY is not used and
> > the BOOTFP resource is adjusted to match the PCI BAR.
> 
> A dmesg log would be nice, but I assume nvidiafb fails because it
> cannot map its BAR regions?

The logs are adjusted and so it the kernel config file.

$ grep nvidiafb *
dm-busy-adjust:nvidiafb_setup START
dm-busy-adjust:nvidiafb_probe START
dm-busy-adjust:nvidiafb 0000:01:00.0: BAR 3: can't reserve [mem
0xf0000000-0xf1ffffff 64bit pref] dm-busy-adjust:nvidiafb: cannot
request PCI regions dm-busy-noadjust:nvidiafb_setup START
dm-busy-noadjust:nvidiafb_probe START
dm-busy-noadjust:nvidiafb 0000:01:00.0: BAR 3: can't reserve [mem
0xf0000000-0xf1ffffff 64bit pref] dm-busy-noadjust:nvidiafb: cannot
request PCI regions dm-nobusy-adjust:nvidiafb_setup START
dm-nobusy-adjust:nvidiafb_probe START
dm-nobusy-adjust:nvidiafb: Device ID: 10de0ffc 
dm-nobusy-adjust:nvidiafb: unknown NV_ARCH
dm-nobusy-noadjust:nvidiafb_setup START
dm-nobusy-noadjust:nvidiafb_probe START
dm-nobusy-noadjust:nvidiafb 0000:01:00.0: BAR 3: can't reserve [mem
0xf0000000-0xf1ffffff 64bit pref] dm-nobusy-noadjust:nvidiafb: cannot
request PCI regions

The error comes from pci_request_regions() called in
drivers/video/nvidia/nvidia.c

> > It means that your patch by itself won't prevent nvidiafb from
> > getting the resource on my hardware (ThinkPad W530).  However, if
> > the BOOTFP resource matches the PCI BAR for the video card, adding
> > IORESOURCE_BUSY might prevent some framebuffer drivers from
> > accessing the resource.
> 
> Meh! I now understand the problem:

Great!

> In other words: The fact that we used to not reserve
> platform-framebuffer regions before 3.12 trips us now because it is
> actually _wrong_ to load real hw drivers like nvidiafb while the
> platform-framebuffer is still available. So the failure we get now
> just tells us that nvidiafb and friends do horrible things.

I actually hoped to hear from you something like that.  It's good to
have limitations if they are well understood and not arbitrary.

> Fortunately, no real DRM drivers actually request pci regions (why
> would they? pci-probing already guarantees exclusive access) and the
> platform-FB drivers have already been converted. So this bug can only
> be triggered with legacy hw-fbdev drivers (a simple search for
> pci_request_regions in ./drivers/video/ shows them).

It's very reassuring.  Your work is greatly appreciated!

-- 
Regards,
Pavel Roskin
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