8612169a05
Add missing cache information to the Rockchip RK356x SoC dtsi, to allow
the userspace, which includes lscpu(1) that uses the virtual files provided
by the kernel under the /sys/devices/system/cpu directory, to display the
proper RK3566 and RK3568 cache information.
Adding the cache information to the RK356x SoC dtsi also makes the following
warning message in the kernel log go away:
cacheinfo: Unable to detect cache hierarchy for CPU 0
The cache parameters for the RK356x dtsi were obtained and partially derived
by hand from the cache size and layout specifications found in the following
datasheets and technical reference manuals:
- Rockchip RK3566 datasheet, version 1.1
- Rockchip RK3568 datasheet, version 1.3
- ARM Cortex-A55 revision r1p0 TRM, version 0100-00
- ARM DynamIQ Shared Unit revision r4p0 TRM, version 0400-02
For future reference, here's a rather detailed summary of the documentation,
which applies to both Rockchip RK3566 and RK3568 SoCs:
- All caches employ the 64-byte cache line length
- Each Cortex-A55 core has 32 KB of L1 4-way, set-associative instruction
cache and 32 KB of L1 4-way, set-associative data cache
- There are no L2 caches, which are per-core and private in Cortex-A55,
because it belongs to the ARM DynamIQ IP core lineup
- The entire SoC has 512 KB of unified L3 16-way, set-associative cache,
which is shared among all four Cortex-A55 CPU cores
- Cortex-A55 cores can be configured without private per-core L2 caches,
in which case the shared L3 cache appears to them as an L2 cache; this
is the case for the RK356x SoCs, so let's use "cache-level = <2>" to
prevent the "huh, no L2 caches, but an L3 cache?" confusion among the
users viewing the data presented to the userspace; another option could
be to have additional 0 KB L2 caches defined, which may be technically
correct, but would probably be even more confusing
Helped-by: Anand Moon <linux.amoon@gmail.com>
Tested-By: Diederik de Haas <didi.debian@cknow.org>
Reviewed-by: Anand Moon <linux.amoon@gmail.com>
Signed-off-by: Dragan Simic <dsimic@manjaro.org>
Link: https://lore.kernel.org/r/2dee6dad8460b0c5f3b5da53cf55f735840efef1.1709957777.git.dsimic@manjaro.org
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
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 reStructuredText 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.