linux-kernel - Re: [PATCH] riscv: cacheinfo: init cache levels via fetch_cache

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Message-ID: <d339833a-5784-407b-816d-ab95d35fbe4e@ghiti.fr>
Date: Thu, 31 Jul 2025 15:29:01 +0200
From: Alexandre Ghiti <alex@...ti.fr>
To: liu.xuemei1@....com.cn, paul.walmsley@...ive.com
Cc: palmer@...belt.com, aou@...s.berkeley.edu, spersvold@...il.com,
 sudeep.holla@....com, mikisabate@...il.com, robh@...nel.org,
 linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] riscv: cacheinfo: init cache levels via fetch_cache_info
 when SMP disabled

Hi Jessica,

On 7/25/25 04:44, liu.xuemei1@....com.cn wrote:
> From: Jessica Liu <liu.xuemei1@....com.cn>
>
> As described in commit 1845d381f280 ("riscv: cacheinfo: Add back
> init_cache_level() function"), when CONFIG_SMP is undefined, the cache
> hierarchy detection needs to be performed through the init_cache_level(),
> whereas when CONFIG_SMP is defined, this detection is handled during the
> init_cpu_topology() process.
>
> Furthermore, while commit 66381d36771e ("RISC-V: Select ACPI PPTT drivers")
> enables cache information retrieval through the ACPI PPTT table, the
> init_of_cache_level() called within init_cache_level() cannot support cache
> hierarchy detection through ACPI PPTT. Therefore, when CONFIG_SMP is
> undefined, we directly invoke the fetch_cache_info function to initialize
> the cache levels.
>
> Signed-off-by: Jessica Liu <liu.xuemei1@....com.cn>
> ---
>   arch/riscv/kernel/cacheinfo.c | 6 +++++-
>   1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/arch/riscv/kernel/cacheinfo.c b/arch/riscv/kernel/cacheinfo.c
> index 26b085dbdd07..f81ca963d177 100644
> --- a/arch/riscv/kernel/cacheinfo.c
> +++ b/arch/riscv/kernel/cacheinfo.c
> @@ -73,7 +73,11 @@ static void ci_leaf_init(struct cacheinfo *this_leaf,
>
>   int init_cache_level(unsigned int cpu)
>   {
> -	return init_of_cache_level(cpu);
> +#ifdef CONFIG_SMP
> +	return 0;
> +#endif
> +
> +	return fetch_cache_info(cpu);
>   }
>
>   int populate_cache_leaves(unsigned int cpu)


Is the current behaviour wrong or just redundant? If wrong, I'll add a 
Fixes tag to backport, otherwise I won't.

Thanks,

Alex