Re: [PATCH] arm64: dts: allwinner: Add cache information to the SoC dtsi for H6
From: Dragan Simic
Date: Mon Apr 29 2024 - 20:02:03 EST
Hello Andre,
On 2024-04-30 01:10, Andre Przywara wrote:
On Sun, 28 Apr 2024 13:40:36 +0200
Dragan Simic <dsimic@xxxxxxxxxxx> wrote:
Add missing cache information to the Allwinner H6 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 H6 cache information.
Adding the cache information to the H6 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 H6 dtsi were obtained and partially
derived
by hand from the cache size and layout specifications found in the
following
datasheets and technical reference manuals:
- Allwinner H6 V200 datasheet, version 1.1
- ARM Cortex-A53 revision r0p3 TRM, version E
For future reference, here's a brief summary of the documentation:
- 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 entire SoC has 512 KB of unified L2 16-way, set-associative
cache
Signed-off-by: Dragan Simic <dsimic@xxxxxxxxxxx>
I can confirm that the data below matches the manuals, but also the
decoding of the architectural cache type registers (CCSIDR_EL1):
L1D: 32 KB: 128 sets, 4 way associative, 64 bytes/line
L1I: 32 KB: 256 sets, 2 way associative, 64 bytes/line
L2: 512 KB: 512 sets, 16 way associative, 64 bytes/line
Thank you very much for reviewing my patch in such a detailed way!
It's good to know that the values in the Allwinner datasheets match
with the observed reality, so to speak. :)
tinymembench results for the H6 are available here:
https://github.com/ThomasKaiser/sbc-bench/blob/master/results/26Ph.txt
and confirm the theory. Also ran it locally with similar results.
Here's a quick copy & paste of the most important benchmark results
from the link above, as a quick reference for anyone reading this
thread in the future, or as a data source in case the link above
becomes inaccessible at some point in the future:
==========================================================================
== Memory latency test
==
==
==
== Average time is measured for random memory accesses in the buffers
==
== of different sizes. The larger is the buffer, the more significant
==
== are relative contributions of TLB, L1/L2 cache misses and SDRAM
==
== accesses. For extremely large buffer sizes we are expecting to see
==
== page table walk with several requests to SDRAM for almost every
==
== memory access (though 64MiB is not nearly large enough to experience
==
== this effect to its fullest).
==
==
==
== Note 1: All the numbers are representing extra time, which needs to
==
== be added to L1 cache latency. The cycle timings for L1 cache
==
== latency can be usually found in the processor documentation.
==
== Note 2: Dual random read means that we are simultaneously performing
==
== two independent memory accesses at a time. In the case if
==
== the memory subsystem can't handle multiple outstanding
==
== requests, dual random read has the same timings as two
==
== single reads performed one after another.
==
==========================================================================
block size : single random read / dual random read, [MADV_NOHUGEPAGE]
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 : 3.8 ns / 6.5 ns
131072 : 5.8 ns / 9.1 ns
262144 : 6.9 ns / 10.2 ns
524288 : 7.8 ns / 11.2 ns
1048576 : 74.3 ns / 114.5 ns
2097152 : 110.5 ns / 148.1 ns
4194304 : 132.6 ns / 164.5 ns
8388608 : 144.0 ns / 172.3 ns
16777216 : 151.5 ns / 177.3 ns
33554432 : 156.3 ns / 180.7 ns
67108864 : 158.7 ns / 182.9 ns
block size : single random read / dual random read, [MADV_HUGEPAGE]
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 : 3.8 ns / 6.5 ns
131072 : 5.8 ns / 9.1 ns
262144 : 6.9 ns / 10.2 ns
524288 : 7.8 ns / 11.2 ns
1048576 : 74.3 ns / 114.5 ns
2097152 : 110.0 ns / 147.5 ns
4194304 : 127.6 ns / 158.3 ns
8388608 : 136.4 ns / 162.2 ns
16777216 : 141.2 ns / 165.6 ns
33554432 : 143.7 ns / 168.4 ns
67108864 : 144.9 ns / 168.9 ns
Reviewed-by: Andre Przywara <andre.przywara@xxxxxxx>
Thanks!
---
arch/arm64/boot/dts/allwinner/sun50i-h6.dtsi | 37
++++++++++++++++++++
1 file changed, 37 insertions(+)
diff --git a/arch/arm64/boot/dts/allwinner/sun50i-h6.dtsi
b/arch/arm64/boot/dts/allwinner/sun50i-h6.dtsi
index d11e5041bae9..1a63066396e8 100644
--- a/arch/arm64/boot/dts/allwinner/sun50i-h6.dtsi
+++ b/arch/arm64/boot/dts/allwinner/sun50i-h6.dtsi
@@ -29,36 +29,73 @@ cpu0: cpu@0 {
clocks = <&ccu CLK_CPUX>;
clock-latency-ns = <244144>; /* 8 32k periods */
#cooling-cells = <2>;
+ 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>;
};
cpu1: cpu@1 {
compatible = "arm,cortex-a53";
device_type = "cpu";
reg = <1>;
enable-method = "psci";
clocks = <&ccu CLK_CPUX>;
clock-latency-ns = <244144>; /* 8 32k periods */
#cooling-cells = <2>;
+ 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>;
};
cpu2: cpu@2 {
compatible = "arm,cortex-a53";
device_type = "cpu";
reg = <2>;
enable-method = "psci";
clocks = <&ccu CLK_CPUX>;
clock-latency-ns = <244144>; /* 8 32k periods */
#cooling-cells = <2>;
+ 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>;
};
cpu3: cpu@3 {
compatible = "arm,cortex-a53";
device_type = "cpu";
reg = <3>;
enable-method = "psci";
clocks = <&ccu CLK_CPUX>;
clock-latency-ns = <244144>; /* 8 32k periods */
#cooling-cells = <2>;
+ 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>;
+ };
+
+ l2_cache: l2-cache {
+ compatible = "cache";
+ cache-level = <2>;
+ cache-unified;
+ cache-size = <0x80000>;
+ cache-line-size = <64>;
+ cache-sets = <512>;
};
};