linux-kernel - [PATCH RFC 0/2] RISC-V: T-Head vector handling

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Date:   Tue, 28 Feb 2023 22:54:33 +0100
From:   Heiko Stuebner <heiko@...ech.de>
To:     palmer@...belt.com
Cc:     linux-riscv@...ts.infradead.org, samuel@...lland.org,
        guoren@...nel.org, christoph.muellner@...ll.eu, heiko@...ech.de,
        conor.dooley@...rochip.com, linux-kernel@...r.kernel.org,
        Heiko Stuebner <heiko.stuebner@...ll.eu>
Subject: [PATCH RFC 0/2] RISC-V: T-Head vector handling

From: Heiko Stuebner <heiko.stuebner@...ll.eu>

As is widely known the T-Head C9xx cores used for example in the
Allwinner D1 implement an older non-ratified variant of the vector spec.

While userspace will probably have a lot more problems implementing
support for both, on the kernel side the needed changes are actually
somewhat small'ish and can be handled via alternatives somewhat nicely.

With this patchset I could run the same userspace program (picked from
some riscv-vector-test repository) that does some vector additions on
both qemu and a d1-nezha board. On both platforms it ran sucessfully and
even produced the same results.

As can be seen in the todo list, there are 2 places where the changed
SR_VS location still needs to be handled in the next revision
(assembly + ALTERNATIVES + constants + probably stringify resulted in
 some grey hair so far already)

ToDo:
- follow along with the base vector patchset
- handle SR_VS access in _save_context and _secondary_start_sbi

Heiko Stuebner (2):
  RISC-V: define the elements of the VCSR vector CSR
  RISC-V: add T-Head vector errata handling

 arch/riscv/Kconfig.erratas           |  13 +++
 arch/riscv/errata/thead/errata.c     |  32 ++++++
 arch/riscv/include/asm/csr.h         |  31 +++++-
 arch/riscv/include/asm/errata_list.h |  62 +++++++++++-
 arch/riscv/include/asm/vector.h      | 139 +++++++++++++++++++++++++--
 5 files changed, 261 insertions(+), 16 deletions(-)

-- 
2.39.0