Re: [PATCH V3 11/20] RISC-V: ACPI: Cache and retrieve the RINTC structure

Sunil V L
2023-03-03T17:58:39Z

On Fri, Mar 03, 2023 at 05:05:56PM +0100, Andrew Jones wrote:
> On Fri, Mar 03, 2023 at 07:06:38PM +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@ventanamicro.com>
> > Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> > ---
> > arch/riscv/include/asm/acpi.h | 9 ++++++
> > arch/riscv/kernel/acpi.c | 56 +++++++++++++++++++++++++++++++++++
> > 2 files changed, 65 insertions(+)
> >
> > diff --git a/arch/riscv/include/asm/acpi.h b/arch/riscv/include/asm/acpi.h
> > index 111a8ed10af1..8be16c1ef7da 100644
> > --- a/arch/riscv/include/asm/acpi.h
> > +++ b/arch/riscv/include/asm/acpi.h
> > @@ -61,6 +61,10 @@ static inline void arch_fix_phys_package_id(int num, u32 slot) { }
> >
> > int acpi_get_riscv_isa(struct acpi_table_header *table,
> > unsigned int cpu, const char **isa);
> > +
> > +struct acpi_madt_rintc *acpi_cpu_get_madt_rintc(int cpu);
> > +
> > +u32 get_acpi_id_for_cpu(int cpu);
> > #else
> > static inline int acpi_get_riscv_isa(struct acpi_table_header *table,
> > unsigned int cpu, const char **isa)
> > @@ -68,6 +72,11 @@ static inline int acpi_get_riscv_isa(struct acpi_table_header *table,
> > return -EINVAL;
> > }
> >
> > +static inline u32 get_acpi_id_for_cpu(int cpu)
> > +{
> > + return -1;
> > +}
>
> Why do we need this stub? I wouldn't expect non-ACPI code to need an ACPI
> ID.
>
> > +
> > #endif /* CONFIG_ACPI */
> >
> > #endif /*_ASM_ACPI_H*/
> > diff --git a/arch/riscv/kernel/acpi.c b/arch/riscv/kernel/acpi.c
> > index 81d448c41714..8b3d68d8225f 100644
> > --- a/arch/riscv/kernel/acpi.c
> > +++ b/arch/riscv/kernel/acpi.c
> > @@ -24,6 +24,62 @@ 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;
>
> Why not cache the data even when its disabled? We also cache the flags so
> we can always check later too.
>
Okay, doesn't harm.

> > +
> > + cpuid = riscv_hartid_to_cpuid(rintc->hart_id);
> > + if (cpuid >= 0 && cpuid < NR_CPUS)
>
> What does it mean for the above check to fail? Bad ACPI tables?
>
This can happen when SMP is disabled but platform has more 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;
> > +}
> > +
> > +/*
> > + * Instead of parsing (and freeing) the ACPI table, cache
> > + * the RINTC structures since they are frequently used
> > + * like in cpuinfo.
> > + */
> > +struct acpi_madt_rintc *acpi_cpu_get_madt_rintc(int cpu)
> > +{
> > + static bool rintc_init_done;
> > +
> > + if (!rintc_init_done) {
> > + if (acpi_init_rintc_array()) {
> > + pr_err("No valid RINTC entries exist\n");
> > + return NULL;
> > + }
> > +
> > + rintc_init_done = true;
> > + }
> > +
> > + return &cpu_madt_rintc[cpu];
> > +}
> > +
> > +u32 get_acpi_id_for_cpu(int cpu)
> > +{
> > + struct acpi_madt_rintc *rintc = acpi_cpu_get_madt_rintc(cpu);
> > +
> > + if (!rintc)
> > + return -1;
>
> Is -1 defined as an invalid ACPI ID? I'm wondering if we shouldn't just
> BUG in acpi_init_rintc_array() if we fail to initialize and then we can
> unconditionally return rintc->uid here.
>
Thanks!. Will update this.