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On ARM64 systems coreboot defers framebuffer allocation to its payload, to be done by a libpayload function call. In this case, coreboot tables still include a framebuffer entry with display format details, but the physical address field is set to zero (as in [1], for example). Unfortunately, this field is not automatically updated when the framebuffer is initialized through libpayload, citing that doing so would invalidate checksums over the entire coreboot table [2]. This can be observed on ARM64 Chromebooks with stock firmware. On a Google Kevin (RK3399), trying to use coreboot framebuffer driver as built-in to the kernel results in a benign error. But on Google Hana (MT8173) and Google Cozmo (MT8183) it causes a hang. When the framebuffer physical address field in the coreboot table is zero, we have no idea where coreboot initialized a framebuffer, or even if it did. Instead of trying to set up a framebuffer located at zero, return ENODEV to indicate that there isn't one. [1] https://review.coreboot.org/c/coreboot/+/17109 [2] https://review.coreboot.org/c/coreboot/+/8797 Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com> Reviewed-by: Julius Werner <jwerner@chromium.org> Link: https://lore.kernel.org/r/20231108182625.46563-1-alpernebiyasak@gmail.com Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>
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.