Re: [PATCH v5 4/4] riscv: implement cache-management errata for T-Head SoCs

[Guo Ren <guoren@kernel.org>]

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

On Thu, Jun 30, 2022 at 6:00 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.
>
> Signed-off-by: Heiko Stuebner <heiko@sntech.de>
> Reviewed-by: Samuel Holland <samuel@sholland.org>
> Tested-by: Samuel Holland <samuel@sholland.org>
> ---
>  arch/riscv/Kconfig.erratas           | 11 +++++++
>  arch/riscv/errata/thead/errata.c     | 20 ++++++++++++
>  arch/riscv/include/asm/errata_list.h | 48 +++++++++++++++++++++++++---
>  3 files changed, 74 insertions(+), 5 deletions(-)
>
> diff --git a/arch/riscv/Kconfig.erratas b/arch/riscv/Kconfig.erratas
> index 457ac72c9b36..3223e533fd87 100644
> --- a/arch/riscv/Kconfig.erratas
> +++ b/arch/riscv/Kconfig.erratas
> @@ -55,4 +55,15 @@ 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
> +       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 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 852283460fb9..cf6bd44db656 100644
> --- a/arch/riscv/errata/thead/errata.c
> +++ b/arch/riscv/errata/thead/errata.c
> @@ -29,6 +29,23 @@ 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)
> +{
> +#ifdef CONFIG_ERRATA_THEAD_CMO
> +       if (arch_id != 0 || impid != 0)
> +               return false;
> +
> +       if (stage == RISCV_ALTERNATIVES_EARLY_BOOT)
> +               return false;
> +
> +       riscv_noncoherent_supported();
> +       return true;
> +#else
> +       return false;
> +#endif
> +}
> +
>  static u32 thead_errata_probe(unsigned int stage,
>                               unsigned long archid, unsigned long impid)
>  {
> @@ -37,6 +54,9 @@ 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 79d89aeeaa6c..19a771085781 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
> @@ -88,17 +89,54 @@ asm volatile(ALTERNATIVE(                                           \
>  #define ALT_THEAD_PMA(_val)
>  #endif
>
> +/*
> + * 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." __stringify(_op) " (a0)\n\t"                             \
>         "add a0, a0, %0\n\t"                                            \
>         "2:\n\t"                                                        \
> -       "bltu a0, %2, 3b\n\t", 0,                                       \
> -               CPUFEATURE_ZICBOM, CONFIG_RISCV_ISA_ZICBOM)             \
> +       "bltu a0, %2, 3b\n\t"                                           \
> +       "nop", 0, CPUFEATURE_ZICBOM, 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"((unsigned long)(_start) & ~((_cachesize) - 1UL)),       \
>             "r"((unsigned long)(_start) + (_size))                      \
> --
> 2.35.1
>


-- 
Best Regards
 Guo Ren

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