linux-kernel - [PATCH v1 0/2] Provide a fraemework for RISC-V ISA extensions

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Date:   Fri, 24 Dec 2021 13:16:30 -0800
From:   Atish Patra <atishp@...shpatra.org>
To:     linux-kernel@...r.kernel.org
Cc:     Atish Patra <atishp@...osinc.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Atish Patra <atishp@...shpatra.org>,
        Anup Patel <anup@...infault.org>,
        Damien Le Moal <damien.lemoal@....com>,
        devicetree@...r.kernel.org, Jisheng Zhang <jszhang@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>,
        linux-riscv@...ts.infradead.org,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Rob Herring <robh+dt@...nel.org>
Subject: [PATCH v1 0/2] Provide a fraemework for RISC-V ISA extensions 

This series implements a generic framework to parse multi-letter ISA
extensions. It introduces a new DT node that can be under /cpus or
individual cpu depends on the platforms with homogeneous or heterogeneous 
harts. This version of the series only allows adds support for homogeneous
harts as there are no platforms with heterogeneous harts yet. However,
the DT binding allows both. 

The patch also indicates the user space about the available ISA extensions
via /proc/cpuinfo. 

Here is the example output of /proc/cpuinfo:
(with debug patches in Qemu and Linux kernel)

/ # cat /proc/cpuinfo 
processor	: 0
hart		: 0
isa		: rv64imafdcsu
isa-ext		: sstc,sscofpmf
mmu		: sv48

processor	: 1
hart		: 1
isa		: rv64imafdcsu
isa-ext		: sstc,sscofpmf
mmu		: sv48

processor	: 2
hart		: 2
isa		: rv64imafdcsu
isa-ext		: sstc,sscofpmf
mmu		: sv48

processor	: 3
hart		: 3
isa		: rv64imafdcsu
isa-ext		: sstc,sscofpmf
mmu		: sv48

Anybody adding support for any new multi-letter extensions should add an
entry to the riscv_isa_ext_id and the isa extension array. 
E.g. The patch[1] adds the support for sscofpmf extension.

[1] https://github.com/atishp04/linux/commit/a23157264118d6fd905fd08d8717c7df03078bb1

Atish Patra (2):
RISC-V: Provide a framework for parsing multi-letter ISA extensions
dt-bindings: riscv: Add DT binding for RISC-V ISA extensions

.../devicetree/bindings/riscv/cpus.yaml       |  9 +++
arch/riscv/include/asm/hwcap.h                | 31 ++++++++++
arch/riscv/kernel/cpu.c                       | 16 +++++
arch/riscv/kernel/cpufeature.c                | 58 ++++++++++++++++++-
4 files changed, 113 insertions(+), 1 deletion(-)

--
2.33.1