Annoying AMDGPU boot-time warning due to simplefb / amdgpu resource clash

[Linus Torvalds]

So this has been going on for a while, and it's quite annoying.

At bootup, my main desktop (Threadripper 3970X with radeon graphics)
now complains about

  resource sanity check: requesting [mem 0xd0000000-0xdfffffff], which
spans more than BOOTFB [mem 0xd0000000-0xd02fffff]

and then gives me a nasty callchain that is basically the amdgpu probe
sequence ending in amdgpu_bo_init() doing the
arch_io_reserve_memtype_wc() which is then what complains.

That "BOOTFB" resource is from sysfb_simplefb.c, and I think what
started triggering this is commit c96898342c38 ("drivers/firmware:
Don't mark as busy the simple-framebuffer IO resource").

Because it turns out that that removed the IORESOURCE_BUSY, which in
turn is what makes the resource conflict code complain about it now,
because

                /*
                 * if a resource is "BUSY", it's not a hardware resource
                 * but a driver mapping of such a resource; we don't want
                 * to warn for those; some drivers legitimately map only
                 * partial hardware resources. (example: vesafb)
                 */

so the issue is that now the resource code - correctly - says "hey,
you have *two* conflicting driver mappings".

And that commit claims it did it because "which can lead to drivers
requesting the same memory resource to fail", but - once again - the
link in the commit that might actually tell more is just one of those
useless patch submission links again.

So who knows why that commit was actually done, but it's causing annoyance.

If simplefb is actually still using that frame buffer, it's a problem.
If it isn't, then maybe that resource should have been released?

I really think that commit c96898342c38 is buggy. It talks about "let
drivers to request it as busy instead", but then it registers a
resource that isn't actually a proper real resource. It's just a
random incomplete chunk of the actual real thing, so it will still
interfere with resource allocation, and in fact now interferes even
with that "set memtype" because of this valid warning.

             Linus