linux-kernel - [RFC PATCH v1 0/1] base/of/cacheinfo: support l1-cache entry in dt

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Message-ID: <20250124152008.313-1-alireza.sanaee@huawei.com>
Date: Fri, 24 Jan 2025 15:20:07 +0000
From: Alireza Sanaee <alireza.sanaee@...wei.com>
To: <robh@...nel.org>, <mark.rutland@....com>, <devicetree@...r.kernel.org>
CC: <linux-kernel@...r.kernel.org>, <jonathan.cameron@...wei.com>,
	<linux-arm-kernel@...ts.infradead.org>,
	<shameerali.kolothum.thodi@...wei.com>, <zhao1.liu@...el.com>,
	<yangyicong@...ilicon.com>, <rrendec@...hat.com>, <catalin.marinas@....com>
Subject: [RFC PATCH v1 0/1] base/of/cacheinfo: support l1-cache entry in dt

This RFC adds support for l1-cache entry in device tree. The changes are
based on the assumptions that nodes will have l1-cache to describe first
cache layer. This patch enable to describe shared caches for SMTs which
is not currently possible about which there were discussions already
[1,2,3].

The question that I am seeking feedback for is to see if this might be a
good way to go about solving this issue? Or instead using phandle and
index in CPU nodes is a better way to go according to prior discussion,
I have another patch this investigates this approach [2]. Apparently,
every single CPU will need to addressed in the cpu-map structure as per
Mark mentioned earlier [4].

Sample device tree:

             cpu@0 {
                        next-level-cache = <0x800b>;
                        phandle = <0x800a>;
                        reg = <0x00>;
                        enable-method = "psci";
                        compatible = "arm,cortex-a57";
                        device_type = "cpu";

                        l1-cache {
                                next-level-cache = <0x8008>;
                                cache-level = <0x01>;
                                d-cache-sets = <0x100>;
                                d-cache-block-size = <0x40>;
                                d-cache-size = <0x10000>;
                                i-cache-sets = <0x100>;
                                i-cache-block-size = <0x40>;
                                i-cache-size = <0x10000>;
                                phandle = <0x800b>;
                        };
                };

                cpu@1 {
                        next-level-cache = <0x8009>;
                        phandle = <0x8007>;
                        reg = <0x01>;
                        enable-method = "psci";
                        compatible = "arm,cortex-a57";
                        device_type = "cpu";

                        l1-cache {
                                next-level-cache = <0x8008>;
                                cache-level = <0x01>;
                                d-cache-sets = <0x100>;
                                d-cache-block-size = <0x40>;
                                d-cache-size = <0x10000>;
                                i-cache-sets = <0x100>;
                                i-cache-block-size = <0x40>;
                                i-cache-size = <0x10000>;
                                phandle = <0x8009>;
                        };

                        l2-cache {
                                next-level-cache = <0x8002>;
                                cache-level = <0x02>;
                                cache-unified;
                                cache-sets = <0x800>;
                                cache-block-size = <0x40>;
                                cache-size = <0x100000>;
                                phandle = <0x8008>;
                        };
                };

1) https://lore.kernel.org/linux-devicetree/CAL_JsqLGEvGBQ0W_B6+5cME1UEhuKXadBB-6=GoN1tmavw9K_w@mail.gmail.com/
2) https://lore.kernel.org/linux-arm-kernel/20250110161057.445-1-alireza.sanaee@huawei.com/
3) https://mail.gnu.org/archive/html/qemu-arm/2025-01/msg00014.html
4) https://lore.kernel.org/linux-arm-kernel/Z4FJZPRg75YIUR2l@J2N7QTR9R3/

Alireza Sanaee (1):
  base/of/cacheinfo: support l1 entry in dt

 drivers/base/cacheinfo.c | 54 +++++++++++++++++++++++++++-------------
 1 file changed, 37 insertions(+), 17 deletions(-)

-- 
2.34.1