On Thu, Mar 4, 2021 at 11:46 AM Will Deacon [off-list ref] wrote:

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On Thu, Mar 04, 2021 at 10:34:43AM +0000, tan.shaopeng@fujitsu.com

wrote:

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On Wed, Mar 3, 2021 at 10:38 AM tan.shaopeng
[off-list ref] wrote:

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+
+config FUJITSU_CACHE
+        tristate "FUJITSU Cache Driver"
+        depends on ARM64_VHE || COMPILE_TEST
+        help
+          FUJITSU Cache Driver
+
+          This driver offers cache functions for A64FX system.
+         Loading this cache driver, control registers will be set to

enable

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+         these functions, and advanced settings registers will be set

by

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default

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+         values. After loading this driver, you can use the default

values of

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the

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+         advanced settings registers or set the advanced settings

registers

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+         from EL0. Unloading this driver, control registers will be

clear to

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+         disable these functions.
+          When built as a module, this will be called as

"fujitsu_cache".

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My feeling is that this code should be in arch/arm64/, as the cache
is generally considered part of the CPU, rather than part of the wider
SoC design, or something that can be controlled separately from the
core kernel and memory management code.

Thanks for your advice. I also would like to hear the opinions from
other soc&arm maintainers, and then consider whether to add this to
arch/arm64/.

Given that all of this is outside of the scope of the architecture, I don't
think that arch/arm64/ is the right place for it. Perhaps this would fit
into the resctrl rework that James has been doing for MPAM?

Indeed, that sounds like a good starting point. I don't understand enough
about either of the two to be sure, but it sounds like there is some overlap
in functionality, and ideally we would have one user interface that can
deal with all the hardware implementations (intel, arm, fujitsu and any
future ones).

I don't know resctrl well and I’m not sure if it can be used for sector cache now.
Also, it seems to me that resctrl has no control with hardware prefetch. 
I will learn more about resctrl.

Best regards, 
Tan Shaopeng
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