linux-kernel - Re: [PATCH 14/24] RISC-V: ACPI: smpboot: Add function to retrieve the hartid

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Date:   Thu, 9 Feb 2023 20:30:40 +0000
From:   Conor Dooley <conor@...nel.org>
To:     Sunil V L <sunilvl@...tanamicro.com>
Cc:     Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <maz@...nel.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Jonathan Corbet <corbet@....net>,
        linux-riscv@...ts.infradead.org, linux-acpi@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        Anup Patel <apatel@...tanamicro.com>,
        Andrew Jones <ajones@...tanamicro.com>,
        Atish Patra <atishp@...osinc.com>
Subject: Re: [PATCH 14/24] RISC-V: ACPI: smpboot: Add function to retrieve
 the hartid

Hey Sunil, Drew,

@drew, a question below that I'm sorta aiming at you...

On Mon, Jan 30, 2023 at 11:52:15PM +0530, Sunil V L wrote:
> hartid is in RINTC structuire in MADT table. Instead of parsing

Nit: missing articles before RINTC and MADT. Also typo "structure".

Perhaps you'd benefit from a spell checker in your git editor.

> the ACPI table every time we need for a cpu, cache it and provide
> a function to read it.
> 
> This is similar to acpi_get_madt_gicc() in arm64.

-ENOTFOUND, do you mean acpi_cpu_get_madt_gicc()?

> 
> Signed-off-by: Sunil V L <sunilvl@...tanamicro.com>
> ---
>  arch/riscv/include/asm/acpi.h | 14 +++++++++++++-
>  arch/riscv/kernel/smpboot.c   | 21 +++++++++++++++++++++
>  2 files changed, 34 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/riscv/include/asm/acpi.h b/arch/riscv/include/asm/acpi.h
> index d1f1e53ec657..69a880b7257a 100644
> --- a/arch/riscv/include/asm/acpi.h
> +++ b/arch/riscv/include/asm/acpi.h
> @@ -65,6 +65,18 @@ int acpi_numa_get_nid(unsigned int cpu);
>  static inline int acpi_numa_get_nid(unsigned int cpu) { return NUMA_NO_NODE; }
>  #endif /* CONFIG_ACPI_NUMA */
>  
> -#endif
> +struct acpi_madt_rintc *acpi_get_madt_rintc(int cpu);
> +struct acpi_madt_rintc *acpi_cpu_get_madt_rintc(int cpu);
> +static inline u32 get_acpi_id_for_cpu(int cpu)
> +{
> +	return	acpi_cpu_get_madt_rintc(cpu)->uid;
> +}
> +#else
> +static inline u32 get_acpi_id_for_cpu(int cpu)
> +{
> +	return -1;
> +}
> +
> +#endif /* CONFIG_ACPI */
>  
>  #endif /*_ASM_ACPI_H*/
> diff --git a/arch/riscv/kernel/smpboot.c b/arch/riscv/kernel/smpboot.c
> index e48cf88d0bc1..3a8b7a9eb5ac 100644
> --- a/arch/riscv/kernel/smpboot.c
> +++ b/arch/riscv/kernel/smpboot.c
> @@ -73,6 +73,25 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
>  
>  #ifdef CONFIG_ACPI
>  static unsigned int cpu_count = 1;
> +static unsigned int intc_count;
> +static struct acpi_madt_rintc cpu_madt_rintc[NR_CPUS];
> +
> +struct acpi_madt_rintc *acpi_get_madt_rintc(int cpu)
> +{
> +	return &cpu_madt_rintc[cpu];
> +}
> +
> +struct acpi_madt_rintc *acpi_cpu_get_madt_rintc(int cpu)
> +{
> +	int i;

Since we are C11 now, you don't even need to declare this outside of the
loop, right?

> +
> +	for (i = 0; i < NR_CPUS; i++) {

@drew, perhaps you know since you were fiddling not too long ago with
cpumask stuff - at what point does for_each_possible_cpu() become
usable?
I had a bit of a poke & couldn't immediately tell if it'd be okay to use
it here.

> +		if (riscv_hartid_to_cpuid(cpu_madt_rintc[i].hart_id) == cpu)
> +			return &cpu_madt_rintc[i];
> +	}
> +	return NULL;

Another nit: newline before return please :)

> +}
> +EXPORT_SYMBOL_GPL(acpi_cpu_get_madt_rintc);
>  
>  static int __init
>  acpi_parse_rintc(union acpi_subtable_headers *header,
> @@ -92,6 +111,8 @@ acpi_parse_rintc(union acpi_subtable_headers *header,
>  	hart = processor->hart_id;
>  	if (hart < 0)
>  		return 0;
> +
> +	cpu_madt_rintc[intc_count++] = *processor;
>  	if (hart == cpuid_to_hartid_map(0)) {
>  		BUG_ON(found_boot_cpu);
>  		found_boot_cpu = 1;
> -- 
> 2.38.0
> 

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