Add missing cache information to the Allwinner H616 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 H616 cache information.
Adding the cache information to the H616 SoC dtsi also makes the
following
warning message in the kernel log go away:
cacheinfo: Unable to detect cache hierarchy for CPU 0
Rather conspicuously, almost no cache-related information is available
in
the publicly available Allwinner H616 datasheet (version 1.0) and H616
user
manual (version 1.0). Thus, the cache parameters for the H616 SoC
dtsi were
obtained and derived by hand from the cache size and layout
specifications
found in the following technical reference manual, and from the cache
size
and die revision hints available from the following community-provided
data
and memory subsystem benchmarks:
- ARM Cortex-A53 revision r0p4 TRM, version J
- Summary of the two available H616 die revisions and their
differences
in cache sizes observed from the CSSIDR_EL1 register readouts,
provided
by Andre Przywara [1][2]
- Tinymembench benchmark results of the H616-based OrangePi Zero 2
SBC,
provided by Thomas Kaiser [3]
For future reference, here's a brief summary of the available
documentation
and the community-provided data and memory subsystem benchmarks:
- All caches employ the 64-byte cache line length
- Each Cortex-A53 core has 32 KB of L1 2-way, set-associative
instruction
cache and 32 KB of L1 4-way, set-associative data cache
- The size of the L2 cache depends on the actual H616 die revision
(there
are two die revisions), so the entire SoC can have either 256 KB
or 1 MB
of unified L2 16-way, set-associative cache [1]
Also for future reference, here's the relevant excerpt from the
community-
provided H616 memory subsystem benchmark, [3] which confirms that 32
KB and
256 KB are the L1 data and L2 cache sizes, respectively:
block size : single random read / dual random read
1024 : 0.0 ns / 0.0 ns
2048 : 0.0 ns / 0.0 ns
4096 : 0.0 ns / 0.0 ns
8192 : 0.0 ns / 0.0 ns
16384 : 0.0 ns / 0.0 ns
32768 : 0.0 ns / 0.0 ns
65536 : 4.3 ns / 7.3 ns
131072 : 6.6 ns / 10.5 ns
262144 : 9.8 ns / 15.2 ns
524288 : 91.8 ns / 142.9 ns
1048576 : 138.6 ns / 188.3 ns
2097152 : 163.0 ns / 204.8 ns
4194304 : 178.8 ns / 213.5 ns
8388608 : 187.1 ns / 217.9 ns
16777216 : 192.2 ns / 220.9 ns
33554432 : 196.5 ns / 224.0 ns
67108864 : 215.7 ns / 259.5 ns
The changes introduced to the H616 SoC dtsi by this patch specify 256
KB as
the L2 cache size. As outlined by Andre Przywara, [2] a follow-up
TF-A patch
will perform runtime adjustment of the device tree data, making the
correct
L2 cache size of 1 MB present in the device tree for the boards based
on the
revision of H616 that actually provides 1 MB of L2 cache.
[1]
https://lore.kernel.org/linux-sunxi/20240430114627.0cfcd14a@xxxxxxxxxxxxxxxxxxxxxxxxxxx/
[2]
https://lore.kernel.org/linux-sunxi/20240501103059.10a8f7de@xxxxxxxxxxxxxxxxxxxxxxxxxxx/
[3]
https://raw.githubusercontent.com/ThomasKaiser/sbc-bench/master/results/4knM.txt
Suggested-by: Andre Przywara <andre.przywara@xxxxxxx>
Helped-by: Andre Przywara <andre.przywara@xxxxxxx>
Signed-off-by: Dragan Simic <dsimic@xxxxxxxxxxx>
---
.../arm64/boot/dts/allwinner/sun50i-h616.dtsi | 37
+++++++++++++++++++
1 file changed, 37 insertions(+)
diff --git a/arch/arm64/boot/dts/allwinner/sun50i-h616.dtsi
b/arch/arm64/boot/dts/allwinner/sun50i-h616.dtsi
index b2e85e52d1a1..4faed88d8909 100644
--- a/arch/arm64/boot/dts/allwinner/sun50i-h616.dtsi
+++ b/arch/arm64/boot/dts/allwinner/sun50i-h616.dtsi
@@ -26,30 +26,67 @@ cpu0: cpu@0 {
reg = <0>;
enable-method = "psci";
clocks = <&ccu CLK_CPUX>;
+ i-cache-size = <0x8000>;
+ i-cache-line-size = <64>;
+ i-cache-sets = <256>;
+ d-cache-size = <0x8000>;
+ d-cache-line-size = <64>;
+ d-cache-sets = <128>;
+ next-level-cache = <&l2_cache>;
