linux-kernel - Re: [PATCH V4 08/23] RISC-V: ACPI: Cache and retrieve the RINTC structure

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Message-ID: <ZC5Al3swBGK1WP0g@sunil-laptop>
Date:   Thu, 6 Apr 2023 09:16:31 +0530
From:   Sunil V L <sunilvl@...tanamicro.com>
To:     Andrew Jones <ajones@...tanamicro.com>
Cc:     linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-riscv@...ts.infradead.org, linux-acpi@...r.kernel.org,
        linux-crypto@...r.kernel.org, platform-driver-x86@...r.kernel.org,
        llvm@...ts.linux.dev, Jonathan Corbet <corbet@....net>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>, Len Brown <lenb@...nel.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Weili Qian <qianweili@...wei.com>,
        Zhou Wang <wangzhou1@...ilicon.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Marc Zyngier <maz@...nel.org>,
        Maximilian Luz <luzmaximilian@...il.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Mark Gross <markgross@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        "David S . Miller" <davem@...emloft.net>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>
Subject: Re: [PATCH V4 08/23] RISC-V: ACPI: Cache and retrieve the RINTC
 structure

On Wed, Apr 05, 2023 at 05:17:48PM +0200, Andrew Jones wrote:
> On Tue, Apr 04, 2023 at 11:50:22PM +0530, Sunil V L wrote:
> > RINTC structures in the MADT provide mapping between the hartid
> > and the CPU. This is required many times even at run time like
> > cpuinfo. So, instead of parsing the ACPI table every time, cache
> > the RINTC structures and provide a function to get the correct
> > RINTC structure for a given cpu.
> > 
> > Signed-off-by: Sunil V L <sunilvl@...tanamicro.com>
> > Acked-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > ---
> >  arch/riscv/include/asm/acpi.h |  2 ++
> >  arch/riscv/kernel/acpi.c      | 60 +++++++++++++++++++++++++++++++++++
> >  2 files changed, 62 insertions(+)
> > 
> > diff --git a/arch/riscv/include/asm/acpi.h b/arch/riscv/include/asm/acpi.h
> > index 9be52b6ffae1..1606dce8992e 100644
> > --- a/arch/riscv/include/asm/acpi.h
> > +++ b/arch/riscv/include/asm/acpi.h
> > @@ -59,6 +59,8 @@ static inline bool acpi_has_cpu_in_madt(void)
> >  
> >  static inline void arch_fix_phys_package_id(int num, u32 slot) { }
> >  
> > +struct acpi_madt_rintc *acpi_cpu_get_madt_rintc(int cpu);
> > +u32 get_acpi_id_for_cpu(int cpu);
> >  #endif /* CONFIG_ACPI */
> >  
> >  #endif /*_ASM_ACPI_H*/
> > diff --git a/arch/riscv/kernel/acpi.c b/arch/riscv/kernel/acpi.c
> > index 81d448c41714..40ab55309c70 100644
> > --- a/arch/riscv/kernel/acpi.c
> > +++ b/arch/riscv/kernel/acpi.c
> > @@ -24,6 +24,66 @@ EXPORT_SYMBOL(acpi_disabled);
> >  int acpi_pci_disabled = 1;	/* skip ACPI PCI scan and IRQ initialization */
> >  EXPORT_SYMBOL(acpi_pci_disabled);
> >  
> > +static struct acpi_madt_rintc cpu_madt_rintc[NR_CPUS];
> > +
> > +static int acpi_parse_madt_rintc(union acpi_subtable_headers *header, const unsigned long end)
> > +{
> > +	struct acpi_madt_rintc *rintc = (struct acpi_madt_rintc *)header;
> > +	int cpuid;
> > +
> > +	if (!(rintc->flags & ACPI_MADT_ENABLED))
> > +		return 0;
> > +
> > +	cpuid = riscv_hartid_to_cpuid(rintc->hart_id);
> > +	/*
> > +	 * When CONFIG_SMP is disabled, mapping won't be created for
> > +	 * all cpus.
> > +	 * CPUs more than NR_CPUS, will be ignored.
> > +	 */
> > +	if (cpuid >= 0 && cpuid < NR_CPUS)
> > +		cpu_madt_rintc[cpuid] = *rintc;
> > +
> > +	return 0;
> > +}
> > +
> > +static int acpi_init_rintc_array(void)
> > +{
> > +	if (acpi_table_parse_madt(ACPI_MADT_TYPE_RINTC, acpi_parse_madt_rintc, 0) > 0)
> > +		return 0;
> > +
> > +	return -ENODEV;
> 
> As Conor pointed out, the errors could be propagated from
> acpi_table_parse_madt(), which could reduce this function to
> 
>  return acpi_table_parse_madt(ACPI_MADT_TYPE_RINTC, acpi_parse_madt_rintc, 0);
> 
> where the '< 0' check would be in the caller below. That sounds good to
> me, but then I'd take that a step further and just drop this helper
> altogether.
> 
Thanks, Conor, Drew. I used similar to how others have used
acpi_table_parse_madt(). But your suggestion makes sense. Will remove
the wrapper function also.

Thanks,
Sunil