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3310288f61
Some DT platforms use EFI to boot and in this case the EFI Boot Services
may register a EFI_GRAPHICS_OUTPUT_PROTOCOL handle, that will later be
queried by the Linux EFI stub to fill the global struct screen_info data.
The data is used by the Generic System Framebuffers (sysfb) framework to
add a platform device with platform data about the system framebuffer.
But if there is a "simple-framebuffer" node in the DT, the OF core will
also do the same and add another device for the system framebuffer.
This could lead for example, to two platform devices ("simple-framebuffer"
and "efi-framebuffer") to be added and matched with their corresponding
drivers. So both efifb and simpledrm will be probed, leading to following:
[ 0.055752] efifb: framebuffer at 0xbd58dc000, using 16000k, total 16000k
[ 0.055755] efifb: mode is 2560x1600x32, linelength=10240, pages=1
[ 0.055758] efifb: scrolling: redraw
[ 0.055759] efifb: Truecolor: size=2:10:10:10, shift=30:20:10:0
...
[ 3.295896] simple-framebuffer bd58dc000.framebuffer: [drm] *ERROR*
could not acquire memory range [??? 0xffff79f30a29ee40-0x2a5000001a7
flags 0x0]: -16
[ 3.298018] simple-framebuffer: probe of bd58dc000.framebuffer
failed with error -16
To prevent the issue, make the OF core to disable sysfb if there is a node
with a "simple-framebuffer" compatible. That way only this device will be
registered and sysfb would not attempt to register another one using the
screen_info data even if this has been filled.
This seems the correct thing to do in this case because:
a) On a DT platform, the DTB is the single source of truth since is what
describes the hardware topology. Even if EFI Boot Services are used to
boot the machine.
b) The of_platform_default_populate_init() function is called in the
arch_initcall_sync() initcall level while the sysfb_init() function
is called later in the subsys_initcall() initcall level.
Reported-by: Andrew Worsley <amworsley@gmail.com>
Closes: https://lore.kernel.org/all/20231111042926.52990-2-amworsley@gmail.com
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://lore.kernel.org/r/20231113085305.1823455-1-javierm@redhat.com
Signed-off-by: Rob Herring <robh@kernel.org>
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.