[PATCH v2 0/2] RISC-V: T-Head vector handling

[Heiko Stuebner]

From: Heiko Stuebner <heiko.stuebner@xxxxxxxx>

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

changes since v1:
- rebase on top of the merged vector patchset
- add separate patch for "has_vector()" variable
- a number of cleanups
- a comment that T-Head cores do not seem to implement the
  vxsat and vxrm fields in the fcsr register


Heiko Stuebner (3):
  RISC-V: define the elements of the VCSR vector CSR
  RISC-V: move vector-available status into a dedicated variable
  RISC-V: add T-Head vector errata handling

 arch/riscv/Kconfig.errata            |  13 +++
 arch/riscv/errata/thead/errata.c     |  32 ++++++
 arch/riscv/include/asm/csr.h         |  29 +++++-
 arch/riscv/include/asm/errata_list.h |  45 ++++++++-
 arch/riscv/include/asm/vector.h      | 144 +++++++++++++++++++++++++--
 arch/riscv/kernel/setup.c            |   6 ++
 arch/riscv/kernel/vector.c           |  10 +-
 7 files changed, 261 insertions(+), 18 deletions(-)

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2.39.2