Re: [PATCH v6 3/6] riscv: errata: Add Andes alternative ports

Conor Dooley
2023-01-06T21:45:02Z

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On Fri, Jan 06, 2023 at 06:55:23PM +0000, Prabhakar wrote:
> From: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
>
> Add required ports of the Alternative scheme for Andes CPU cores.
>
> I/O Coherence Port (IOCP) provides an AXI interface for connecting external
> non-caching masters, such as DMA controllers. IOCP is a specification
> option and is disabled on the Renesas RZ/Five SoC due to this reason cache
> management needs a software workaround.
>
> Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
> ---
> v5 -> v6
> * Dropped patching alternative and now just probing IOCP
>
> v4 -> v5
> * Sorted the Kconfig/Makefile/Switch based on Core name
> * Added a comments
> * Introduced RZFIVE_SBI_EXT_IOCP_SW_WORKAROUND SBI EXT ID to check if
> CMO needs to be applied. Is there a way we can access the DTB while patching
> as we can drop this SBI EXT ID and add a DT property instead for cmo?
>
> RFC v3 -> v4
> * New patch
> ---
> arch/riscv/Kconfig.erratas | 22 +++++++++
> arch/riscv/errata/Makefile | 1 +
> arch/riscv/errata/andes/Makefile | 1 +
> arch/riscv/errata/andes/errata.c | 71 ++++++++++++++++++++++++++++
> arch/riscv/include/asm/alternative.h | 3 ++
> arch/riscv/kernel/alternative.c | 5 ++
> 6 files changed, 103 insertions(+)
> create mode 100644 arch/riscv/errata/andes/Makefile
> create mode 100644 arch/riscv/errata/andes/errata.c
>
> diff --git a/arch/riscv/Kconfig.erratas b/arch/riscv/Kconfig.erratas
> index 69621ae6d647..f0f0c1abd52b 100644
> --- a/arch/riscv/Kconfig.erratas
> +++ b/arch/riscv/Kconfig.erratas
> @@ -1,5 +1,27 @@
> menu "CPU errata selection"
>
> +config ERRATA_ANDES
> + bool "Andes AX45MP errata"
> + depends on !XIP_KERNEL
> + select RISCV_ALTERNATIVE
> + help
> + All Andes errata Kconfig depend on this Kconfig. Disabling
> + this Kconfig will disable all Andes errata. Please say "Y"
> + here if your platform uses Andes CPU cores.
> +
> + Otherwise, please say "N" here to avoid unnecessary overhead.
> +
> +config ERRATA_ANDES_CMO
> + bool "Apply Andes cache management errata"
> + depends on ERRATA_ANDES && MMU && ARCH_R9A07G043
> + select RISCV_DMA_NONCOHERENT
> + default y
> + help
> + This will apply the cache management errata to handle the
> + non-standard handling on non-coherent operations on Andes cores.
> +
> + If you don't know what to do here, say "Y".

Ideally we would not need errata to turn this stuff on at all, but, as
you pointed out to me off-list, arch_setup_dma_ops() complains if we
have not set up.

I'm happy to commit to trying to sort that out in follow on work w/ MPFS,
since in that case it really isn't errata, and not require it for this
series as you do fit that particular bill IMO.

Reviewed-by: Conor Dooley <conor.dooley@microchip.com>

Thanks,
Conor.

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