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Message-ID: <252b1cc5a04fb5d3703388df1470b9b3@manjaro.org>
Date: Tue, 28 May 2024 18:47:02 +0200
From: Dragan Simic <dsimic@...jaro.org>
To: wens@...e.org
Cc: linux-sunxi@...ts.linux.dev, jernej.skrabec@...il.com,
samuel@...lland.org, linux-arm-kernel@...ts.infradead.org,
devicetree@...r.kernel.org, robh@...nel.org, krzk+dt@...nel.org,
conor+dt@...nel.org, linux-kernel@...r.kernel.org, Andre Przywara
<andre.przywara@....com>
Subject: Re: [PATCH] arm64: dts: allwinner: Add cache information to the SoC
dtsi for H616
On 2024-05-28 18:08, Chen-Yu Tsai wrote:
> On Fri, May 3, 2024 at 5:09 PM Dragan Simic <dsimic@...jaro.org> wrote:
>>
>> 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@donnerap.manchester.arm.com/
>> [2]
>> https://lore.kernel.org/linux-sunxi/20240501103059.10a8f7de@donnerap.manchester.arm.com/
>> [3]
>> https://raw.githubusercontent.com/ThomasKaiser/sbc-bench/master/results/4knM.txt
>>
>> Suggested-by: Andre Przywara <andre.przywara@....com>
>> Helped-by: Andre Przywara <andre.przywara@....com>
>> Signed-off-by: Dragan Simic <dsimic@...jaro.org>
>> ---
>> .../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>;
>
> This no longer applies due to the CPU DVFS stuff getting merged.
> Can you rebase and resend?
Sure, just sent the rebased version as the v2. [1]
[1]
https://lore.kernel.org/linux-sunxi/e4b9cc3e3d366a571e552c31dafa5de847bc1c12.1716914537.git.dsimic@manjaro.org/
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