[PATCH 0/9] T-Head: Allow read access to th.mxstatus CSR

[Anup Patel]

Hi Christoph,

On Wed, Mar 27, 2024 at 3:41 PM Christoph Müllner
<christoph.muellner at vrull.eu> wrote:
>
> On T-Head C9xx harts, the th.mxstatus CSR provides valuable information
> about the available vendor extensions. As this CSR is only accessible in
> M-mode, we need to provide a mechanism for other modes to access this
> information. This patchset solves this by extending the existing
> platform abstraction such that platforms (or platform overrides)
> can provide a CSR read/write handler.
>
> A CSR read-handler for th.mxstatus is then added that is utilized by
> the Allwinner D1, the T-Head TH1520, and the Sophgo SG2042.
> Further, a generic mvendorid-based platform override is added that also
> enables the CSR read-handler for th.mxstatus (needed for QEMU).
>
> The CSR is documented here:
>   https://github.com/T-head-Semi/thead-extension-spec/pull/45
>
> For QEMU this patch depends on
>   https://lists.gnu.org/archive/html/qemu-devel/2024-03/msg06368.html
>
> Christoph Müllner (9):
>   sbi_platform: Add mechanism to handle CSR reads/writes in platform
>   platform: generic: Add mechanism to handle CSR reads/writes in
>     overrides
>   lib: sbi_emulate_csr: Utilize platform hooks for unknown CSRs
>   platform: generic: thead: Add CSR read handler for T-Head C9xx
>   {allwinner/sun20i-d1,sophgo/sg2042,thead-generic}: Enable T-Head CSR
>     read access
>   platform: thead: Rename thead-generic to thead-th1520
>   platform: generic: Add mechanism to match via mvendorid
>   platform: generic: thead: Add definition of T-Head's vendor ID
>   platform: generic: Add generic T-Head override

There is no activity on this series so I assume it is abandoned.

My only comment is that exposing M-mode CSRs to S-mode via
CSR trap-n-emulate has been discouraged. If you really require
to expose read-only information to supervisor software then prefer
DT/ACPI.

Regards,
Anup

>
>  include/sbi/sbi_platform.h                    | 48 +++++++++++++++
>  lib/sbi/sbi_emulate_csr.c                     |  8 ++-
>  platform/generic/Kconfig                      | 12 +++-
>  platform/generic/allwinner/sun20i-d1.c        |  2 +
>  platform/generic/configs/defconfig            |  3 +-
>  platform/generic/include/platform_override.h  |  5 ++
>  platform/generic/include/thead/c9xx_csr.h     | 16 +++++
>  .../generic/include/thead/c9xx_encoding.h     |  2 +
>  platform/generic/platform.c                   | 58 ++++++++++++++++++-
>  platform/generic/sophgo/sg2042.c              |  2 +
>  platform/generic/thead/Kconfig                |  4 ++
>  platform/generic/thead/objects.mk             |  9 ++-
>  platform/generic/thead/thead-generic.c        | 42 +++-----------
>  platform/generic/thead/thead-th1520.c         | 55 ++++++++++++++++++
>  platform/generic/thead/thead_c9xx_csr.c       | 30 ++++++++++
>  15 files changed, 252 insertions(+), 44 deletions(-)
>  create mode 100644 platform/generic/include/thead/c9xx_csr.h
>  create mode 100644 platform/generic/thead/thead-th1520.c
>  create mode 100644 platform/generic/thead/thead_c9xx_csr.c
>
> --
> 2.44.0
>
>
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