video/aperture: Provide a VGA helper for gma500 and internal use

The hardware for gma500 is different from the rest, as it uses stolen
framebuffer memory that is not available via PCI BAR. The regular PCI
removal helper cannot detect the framebuffer, while the non-PCI helper
misses possible conflicting VGA devices (i.e., a framebuffer or text
console).

Gma500 therefore calls both helpers to catch all cases. It's confusing
as it implies that there's something about the PCI device that requires
ownership management. The relationship between the PCI device and the
VGA devices is non-obvious. At worst, readers might assume that calling
two functions for clearing aperture ownership is a bug in the driver.

Hence, move the PCI removal helper's code for VGA functionality into
a separate function and call this function from gma500. Documents the
purpose of each call to aperture helpers. The change contains comments
and example code form the discussion at [1].

v5:
* fix grammar in gma500 comment (Javier)

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.kernel.org/project/dri-devel/patch/20230404201842.567344-1-daniel.vetter@ffwll.ch/ # 1
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230406132109.32050-10-tzimmermann@suse.de

video/aperture: Only remove sysfb on the default vga pci device

Instead of calling aperture_remove_conflicting_devices() to remove the
conflicting devices, just call to aperture_detach_devices() to detach
the device that matches the same PCI BAR / aperture range. Since the
former is just a wrapper of the latter plus a sysfb_disable() call,
and now that's done in this function but only for the primary devices.

This fixes a regression introduced by commit ee7a69aa38d8 ("fbdev:
Disable sysfb device registration when removing conflicting FBs"),
where we remove the sysfb when loading a driver for an unrelated pci
device, resulting in the user losing their efifb console or similar.

Note that in practice this only is a problem with the nvidia blob,
because that's the only gpu driver people might install which does not
come with an fbdev driver of it's own. For everyone else the real gpu
driver will restore a working console.

Also note that in the referenced bug there's confusion that this same
bug also happens on amdgpu. But that was just another amdgpu specific
regression, which just happened to happen at roughly the same time and
with the same user-observable symptoms. That bug is fixed now, see
https://bugzilla.kernel.org/show_bug.cgi?id=216331#c15

Note that we should not have any such issues on non-pci multi-gpu
issues, because I could only find two such cases:
- SoC with some external panel over spi or similar. These panel
drivers do not use drm_aperture_remove_conflicting_framebuffers(),
so no problem.
- vga+mga, which is a direct console driver and entirely bypasses all
this.

For the above reasons the cc: stable is just notionally, this patch
will need a backport and that's up to nvidia if they care enough.

v2:
- Explain a bit better why other multi-gpu that aren't pci shouldn't
have any issues with making all this fully pci specific.

v3
- polish commit message (Javier)

v4:
- Fix commit message style (i.e., commit 1234 ("..."))
- fix Daniel's S-o-b address

v5:
- add back an S-o-b tag with Daniel's Intel address

Fixes: ee7a69aa38d8 ("fbdev: Disable sysfb device registration when removing conflicting FBs")
Tested-by: Aaron Plattner <aplattner@nvidia.com>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=216303#c28
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Aaron Plattner <aplattner@nvidia.com>
Cc: Javier Martinez Canillas <javierm@redhat.com>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Helge Deller <deller@gmx.de>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: <stable@vger.kernel.org> # v5.19+ (if someone else does the backport)
Link: https://patchwork.freedesktop.org/patch/msgid/20230406132109.32050-8-tzimmermann@suse.de

video/aperture: Drop primary argument

With the preceding patches it's become defunct. Also I'm about to add
a different boolean argument, so it's better to keep the confusion
down to the absolute minimum.

v2: Since the hypervfb patch got droppped (it's only a pci device for
gen1 vm, not for gen2) there is one leftover user in an actual driver
left to touch.

v4:
- fixes to commit message
- fix Daniel's S-o-b address

v5:
- add back an S-o-b tag with Daniel's Intel address

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Javier Martinez Canillas <javierm@redhat.com>
Cc: Helge Deller <deller@gmx.de>
Cc: linux-fbdev@vger.kernel.org
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Wei Liu <wei.liu@kernel.org>
Cc: Dexuan Cui <decui@microsoft.com>
Cc: linux-hyperv@vger.kernel.org
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230406132109.32050-7-tzimmermann@suse.de

video/aperture: Move vga handling to pci function

A few reasons for this:

- It's really the only one where this matters. I tried looking around,
and I didn't find any non-pci vga-compatible controllers for x86
(since that's the only platform where we had this until a few
patches ago), where a driver participating in the aperture claim
dance would interfere.

- I also don't expect that any future bus anytime soon will
not just look like pci towards the OS, that's been the case for like
25+ years by now for practically everything (even non non-x86).

- Also it's a bit funny if we have one part of the vga removal in the
pci function, and the other in the generic one.

v2: Rebase.

v4:
- fix Daniel's S-o-b address

v5:
- add back an S-o-b tag with Daniel's Intel address

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Javier Martinez Canillas <javierm@redhat.com>
Cc: Helge Deller <deller@gmx.de>
Cc: linux-fbdev@vger.kernel.org
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230406132109.32050-6-tzimmermann@suse.de

video/aperture: Only kick vgacon when the pdev is decoding vga

Otherwise it's a bit silly, and we might throw out the driver for the
screen the user is actually looking at. I haven't found a bug report
for this case yet, but we did get bug reports for the analog case
where we're throwing out the efifb driver.

v2: Flip the check around to make it clear it's a special case for
kicking out the vgacon driver only (Thomas)

v4:
- fixes to commit message
- fix Daniel's S-o-b address

v5:
- add back an S-o-b tag with Daniel's Intel address

Link: https://bugzilla.kernel.org/show_bug.cgi?id=216303
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Javier Martinez Canillas <javierm@redhat.com>
Cc: Helge Deller <deller@gmx.de>
Cc: linux-fbdev@vger.kernel.org
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230406132109.32050-5-tzimmermann@suse.de

video/aperture: use generic code to figure out the vga default device

Since vgaarb has been promoted to be a core piece of the pci subsystem
we don't have to open code random guesses anymore, we actually know
this in a platform agnostic way, and there's no need for an x86
specific hack. See also commit 1d38fe6ee6a8 ("PCI/VGA: Move vgaarb to
drivers/pci")

This should not result in any functional change, and the non-x86
multi-gpu pci systems are probably rare enough to not matter (I don't
know of any tbh). But it's a nice cleanup, so let's do it.

There's been a few questions on previous iterations on dri-devel and
irc:

- fb_is_primary_device() seems to be yet another implementation of
this theme, and at least on x86 it checks for both
vga_default_device OR rom shadowing. There shouldn't ever be a case
where rom shadowing gives any additional hints about the boot vga
device, but if there is then the default vga selection in vgaarb
should probably be fixed. And not special-case checks replicated all
over.

- Thomas also brought up that on most !x86 systems
fb_is_primary_device() returns 0, except on sparc/parisc. But these
2 special cases are about platform specific devices and not pci, so
shouldn't have any interactions.

- Furthermore fb_is_primary_device() is a bit a red herring since it's
only used to select the right fbdev driver for fbcon, and not for
the fw handover dance which the aperture helpers handle. At least
for x86 we might want to look into unifying them, but that's a
separate thing.

v2: Extend commit message trying to summarize various discussions.

v4:
- make the test for the primary device easier to read (Javier)
- fix commit message style (i.e., commit 1234 ("..."))
- fix Daniel's S-o-b address

v5:
- add back an S-o-b tag with Daniel's Intel address

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Javier Martinez Canillas <javierm@redhat.com>
Cc: Helge Deller <deller@gmx.de>
Cc: linux-fbdev@vger.kernel.org
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: linux-pci@vger.kernel.org
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230406132109.32050-3-tzimmermann@suse.de

video/aperture: Fix typos in comments

EFI FB, VESA FB or VGA FB etc belong to firmware based framebuffer driver.

Signed-off-by: Sui Jingfeng <suijingfeng@loongson.cn>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230404040101.2165600-1-suijingfeng@loongson.cn

fbdev/core: Avoid uninitialized read in aperture_remove_conflicting_pci_device()

Return on error directly from the BAR-iterating loop instead of
break+return.

This is actually a cosmetic fix, since it would be highly unusual to
have this called for a PCI device without any memory BARs.

Fixes: 9d69ef183815 ("fbdev/core: Remove remove_conflicting_pci_framebuffers()")
Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/e75323732bedc46d613d72ecb40f97e3bc75eea8.1666829073.git.mirq-linux@rere.qmqm.pl

fbdev: Remove conflict-handling code

Remove the call to do_remove_conflicting_framebuffers() from the
framebuffer registration. Aperture helpers take care of removing
conflicting devices. With all ownership information stored in the
aperture datastrcutures, remove remove_conflicting_framebuffers()
entirely.

This change also rectifies DRM generic-framebuffer registration, which
tried to unregister conflicting framebuffers, even though it's entirely
build on top of DRM.

v2:
* remove internal aperture-overlap helpers, which are
now unused

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220718072322.8927-12-tzimmermann@suse.de

video/aperture: Remove conflicting VGA devices, if any

On the primary graphics adapter, a driver might conflict with a VGA
driver that controls the VGA framebuffer I/O range. Remove the VGA
driver from the aperture helpers. Until now, this case has been
hendled by fbdev, but it should work even with fbdev disabled.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220718072322.8927-10-tzimmermann@suse.de

video/aperture: Disable and unregister sysfb devices via aperture helpers

Call sysfb_disable() before removing conflicting devices in aperture
helpers. Fixes sysfb state if fbdev has been disabled.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Fixes: fb84efa28a48 ("drm/aperture: Run fbdev removal before internal helpers")
Cc: Zack Rusin <zackr@vmware.com>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Javier Martinez Canillas <javierm@redhat.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Helge Deller <deller@gmx.de>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Zhen Lei <thunder.leizhen@huawei.com>
Cc: Changcheng Deng <deng.changcheng@zte.com.cn>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: dri-devel@lists.freedesktop.org
Link: https://patchwork.freedesktop.org/patch/msgid/20220718072322.8927-8-tzimmermann@suse.de

fbdev/core: Remove remove_conflicting_pci_framebuffers()

Remove remove_conflicting_pci_framebuffers() and implement similar
functionality in aperture_remove_conflicting_pci_device(), which was
the only caller. Removes an otherwise unused interface and streamlines
the aperture helper. No functional changes.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220718072322.8927-5-tzimmermann@suse.de

drm: Implement DRM aperture helpers under video/

Implement DRM's aperture helpers under video/ for sharing with other
sub-systems. Remove DRM-isms from the interface. The helpers track
the ownership of framebuffer apertures and provide hand-over from
firmware, such as EFI and VESA, to native graphics drivers.

Other subsystems, such as fbdev and vfio, also have to maintain ownership
of framebuffer apertures. Moving DRM's aperture helpers to a more public
location allows all subsystems to interact with each other and share a
common implementation.

The aperture helpers are selected by the various firmware drivers within
DRM and fbdev, and the VGA text-console driver.

The original DRM interface is kept in place for use by DRM drivers.

v3:
* prefix all interfaces with aperture_ (Javier)
* rework and simplify documentation (Javier)
* rename struct dev_aperture to struct aperture_range
* rebase onto latest DRM
* update MAINTAINERS entry

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Tested-by: Laszlo Ersek <lersek@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220622140134.12763-3-tzimmermann@suse.de