mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2026-05-05 21:44:23 -04:00
0634a2dc95
Raspberry Pi's firmware has a feature to select how much memory to
reserve for its GPU called 'gpu_mem'. The possible values go from 16MB
to 944MB, with a default of 64MB. This memory resides in the topmost
part of the lower 1GB memory area and grows bigger expanding towards the
begging of memory.
It turns out that with low 'gpu_mem' values (16MB and 32MB) the size of
the memory available to the system in the lower 1GB area can outgrow the
interconnect's dma-range as its size was selected based on the maximum
system memory available given the default gpu_mem configuration. This
makes that memory slice unavailable for DMA. And may cause nasty kernel
warnings if CMA happens to include it.
Change soc's dma-ranges to really reflect it's HW limitation, which is
being able to only DMA to the lower 1GB area.
Fixes: 7dbe8c62ce ("ARM: dts: Add minimal Raspberry Pi 4 support")
Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Reviewed-by: Phil Elwell <phil@raspberrypi.org>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
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.