Re: [PATCH v2 3/3] riscv: implement cache-management errata for T-Head SoCs

Anup Patel
2022-05-12T04:41:34Z

On Thu, May 12, 2022 at 3:11 AM Heiko Stuebner <heiko@sntech.de> wrote:
>
> The T-Head C906 and C910 implement a scheme for handling
> cache operations different from the generic Zicbom extension.
>
> Add an errata for it next to the generic dma coherency ops.
>
> Tested-by: Samuel Holland <samuel@sholland.org>
> Signed-off-by: Heiko Stuebner <heiko@sntech.de>

Looks good to me.

Reviewed-by: Anup Patel <anup@brainfault.org>

Regards,
Anup

> ---
> arch/riscv/Kconfig.erratas | 10 ++++++
> arch/riscv/errata/thead/errata.c | 5 +++
> arch/riscv/include/asm/errata_list.h | 47 +++++++++++++++++++++++++---
> 3 files changed, 58 insertions(+), 4 deletions(-)
>
> diff --git a/arch/riscv/Kconfig.erratas b/arch/riscv/Kconfig.erratas
> index ebfcd5cc6eaf..213629bac5d7 100644
> --- a/arch/riscv/Kconfig.erratas
> +++ b/arch/riscv/Kconfig.erratas
> @@ -54,4 +54,14 @@ config ERRATA_THEAD_PBMT
>
> If you don't know what to do here, say "Y".
>
> +config ERRATA_THEAD_CMO
> + bool "Apply T-Head cache management errata"
> + depends on ERRATA_THEAD && RISCV_ISA_ZICBOM
> + default y
> + help
> + This will apply the cache management errata to handle the
> + non-standard handling on non-coherent operations on T-Head SoCs.
> +
> + If you don't know what to do here, say "Y".
> +
> endmenu
> diff --git a/arch/riscv/errata/thead/errata.c b/arch/riscv/errata/thead/errata.c
> index e5d75270b99c..9545f43d3504 100644
> --- a/arch/riscv/errata/thead/errata.c
> +++ b/arch/riscv/errata/thead/errata.c
> @@ -33,6 +33,11 @@ static const struct errata_info errata_list[ERRATA_THEAD_NUMBER] = {
> .stage = RISCV_ALTERNATIVES_EARLY_BOOT,
> .check_func = errata_mt_check_func
> },
> + {
> + .name = "cache-management",
> + .stage = RISCV_ALTERNATIVES_BOOT,
> + .check_func = errata_mt_check_func
> + },
> };
>
> static u32 thead_errata_probe(unsigned int stage, unsigned long archid, unsigned long impid)
> diff --git a/arch/riscv/include/asm/errata_list.h b/arch/riscv/include/asm/errata_list.h
> index eebcd4415049..1da311fc5126 100644
> --- a/arch/riscv/include/asm/errata_list.h
> +++ b/arch/riscv/include/asm/errata_list.h
> @@ -16,7 +16,8 @@
>
> #ifdef CONFIG_ERRATA_THEAD
> #define ERRATA_THEAD_PBMT 0
> -#define ERRATA_THEAD_NUMBER 1
> +#define ERRATA_THEAD_CMO 1
> +#define ERRATA_THEAD_NUMBER 2
> #endif
>
> #define CPUFEATURE_SVPBMT 0
> @@ -111,8 +112,37 @@ asm volatile(ALTERNATIVE( \
> #define CBO_CLEAN_A0 ".long 0x25200F"
> #define CBO_FLUSH_A0 ".long 0x05200F"
>
> +/*
> + * dcache.ipa rs1 (invalidate, physical address)
> + * | 31 - 25 | 24 - 20 | 19 - 15 | 14 - 12 | 11 - 7 | 6 - 0 |
> + * 0000001 01010 rs1 000 00000 0001011
> + * dache.iva rs1 (invalida, virtual address)
> + * 0000001 00110 rs1 000 00000 0001011
> + *
> + * dcache.cpa rs1 (clean, physical address)
> + * | 31 - 25 | 24 - 20 | 19 - 15 | 14 - 12 | 11 - 7 | 6 - 0 |
> + * 0000001 01001 rs1 000 00000 0001011
> + * dcache.cva rs1 (clean, virtual address)
> + * 0000001 00100 rs1 000 00000 0001011
> + *
> + * dcache.cipa rs1 (clean then invalidate, physical address)
> + * | 31 - 25 | 24 - 20 | 19 - 15 | 14 - 12 | 11 - 7 | 6 - 0 |
> + * 0000001 01011 rs1 000 00000 0001011
> + * dcache.civa rs1 (... virtual address)
> + * 0000001 00111 rs1 000 00000 0001011
> + *
> + * sync.s (make sure all cache operations finished)
> + * | 31 - 25 | 24 - 20 | 19 - 15 | 14 - 12 | 11 - 7 | 6 - 0 |
> + * 0000000 11001 00000 000 00000 0001011
> + */
> +#define THEAD_INVAL_A0 ".long 0x0265000b"
> +#define THEAD_CLEAN_A0 ".long 0x0245000b"
> +#define THEAD_FLUSH_A0 ".long 0x0275000b"
> +#define THEAD_SYNC_S ".long 0x0190000b"
> +
> #define ALT_CMO_OP(_op, _start, _size, _cachesize) \
> -asm volatile(ALTERNATIVE( \
> +asm volatile(ALTERNATIVE_2( \
> + "nop\n\t" \
> "nop\n\t" \
> "nop\n\t" \
> "nop\n\t" \
> @@ -124,8 +154,17 @@ asm volatile(ALTERNATIVE( \
> CBO_##_op##_A0 "\n\t" \
> "add a0, a0, %0\n\t" \
> "2:\n\t" \
> - "bltu a0, %2, 3b\n\t", 0, \
> - CPUFEATURE_CMO, CONFIG_RISCV_ISA_ZICBOM) \
> + "bltu a0, %2, 3b\n\t" \
> + "nop", 0, CPUFEATURE_CMO, CONFIG_RISCV_ISA_ZICBOM, \
> + "mv a0, %1\n\t" \
> + "j 2f\n\t" \
> + "3:\n\t" \
> + THEAD_##_op##_A0 "\n\t" \
> + "add a0, a0, %0\n\t" \
> + "2:\n\t" \
> + "bltu a0, %2, 3b\n\t" \
> + THEAD_SYNC_S, THEAD_VENDOR_ID, \
> + ERRATA_THEAD_CMO, CONFIG_ERRATA_THEAD_CMO) \
> : : "r"(_cachesize), \
> "r"(ALIGN((_start), (_cachesize))), \
> "r"(ALIGN((_start) + (_size), (_cachesize))))
> --
> 2.35.1
>