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

Guo Ren
2022-06-10T01:05:12Z

Reviewed-by: Guo Ren <guoren@kernel.org>

On Fri, Jun 10, 2022 at 8:43 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>
> Reviewed-by: Anup Patel <anup@brainfault.org>
> Signed-off-by: Heiko Stuebner <heiko@sntech.de>
> ---
> arch/riscv/Kconfig.erratas | 10 ++++++
> arch/riscv/errata/thead/errata.c | 15 +++++++++
> arch/riscv/include/asm/errata_list.h | 48 +++++++++++++++++++++++++---
> 3 files changed, 68 insertions(+), 5 deletions(-)
>
> diff --git a/arch/riscv/Kconfig.erratas b/arch/riscv/Kconfig.erratas
> index 457ac72c9b36..4a390035abc7 100644
> --- a/arch/riscv/Kconfig.erratas
> +++ b/arch/riscv/Kconfig.erratas
> @@ -55,4 +55,14 @@ 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 b37b6fedd53b..a3b3612d19df 100644
> --- a/arch/riscv/errata/thead/errata.c
> +++ b/arch/riscv/errata/thead/errata.c
> @@ -27,6 +27,18 @@ static bool errata_probe_pbmt(unsigned int stage,
> return false;
> }
>
> +static bool errata_probe_cmo(unsigned int stage,
> + unsigned long arch_id, unsigned long impid)
> +{
> + if (arch_id != 0 || impid != 0)
> + return false;
> +
> + if (stage == RISCV_ALTERNATIVES_EARLY_BOOT)
> + return false;
> +
> + return true;
> +}
> +
> static u32 thead_errata_probe(unsigned int stage,
> unsigned long archid, unsigned long impid)
> {
> @@ -35,6 +47,9 @@ static u32 thead_errata_probe(unsigned int stage,
> if (errata_probe_pbmt(stage, archid, impid))
> cpu_req_errata |= (1U << ERRATA_THEAD_PBMT);
>
> + if (errata_probe_cmo(stage, archid, impid))
> + cpu_req_errata |= (1U << ERRATA_THEAD_CMO);
> +
> return cpu_req_errata;
> }
>
> diff --git a/arch/riscv/include/asm/errata_list.h b/arch/riscv/include/asm/errata_list.h
> index 2e80a75b5241..a48605d55c3c 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
> @@ -105,17 +106,54 @@ 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( \
> - __nops(5), \
> +asm volatile(ALTERNATIVE_2( \
> + __nops(6), \
> "mv a0, %1\n\t" \
> "j 2f\n\t" \
> "3:\n\t" \
> 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
>

--
Best Regards
Guo Ren

ML: https://lore.kernel.org/linux-csky/