Re: [PATCH 13/24] RISC-V: ACPI: smpboot: Add ACPI support in smp_setup()

[Conor Dooley <conor@kernel.org>]

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On Mon, Jan 30, 2023 at 11:52:14PM +0530, Sunil V L wrote:
> Add function to parse the RINTC structure in
> the MADT table and create the required initializations to
> enable SMP boot on ACPI based platforms.
> 
> Signed-off-by: Sunil V L <sunilvl@ventanamicro.com>
> ---
>  arch/riscv/include/asm/acpi.h |  7 ++++
>  arch/riscv/kernel/smpboot.c   | 73 ++++++++++++++++++++++++++++++++++-
>  2 files changed, 79 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/riscv/include/asm/acpi.h b/arch/riscv/include/asm/acpi.h
> index c5cb9f96d404..d1f1e53ec657 100644
> --- a/arch/riscv/include/asm/acpi.h
> +++ b/arch/riscv/include/asm/acpi.h
> @@ -58,6 +58,13 @@ static inline bool acpi_has_cpu_in_madt(void)
>  }
>  
>  static inline void arch_fix_phys_package_id(int num, u32 slot) { }
> +
> +#ifdef CONFIG_ACPI_NUMA
> +int acpi_numa_get_nid(unsigned int cpu);
> +#else
> +static inline int acpi_numa_get_nid(unsigned int cpu) { return NUMA_NO_NODE; }
> +#endif /* CONFIG_ACPI_NUMA */
> +
>  #endif
>  
>  #endif /*_ASM_ACPI_H*/
> diff --git a/arch/riscv/kernel/smpboot.c b/arch/riscv/kernel/smpboot.c
> index 26214ddefaa4..e48cf88d0bc1 100644
> --- a/arch/riscv/kernel/smpboot.c
> +++ b/arch/riscv/kernel/smpboot.c
> @@ -8,6 +8,7 @@
>   * Copyright (C) 2017 SiFive
>   */
>  
> +#include <linux/acpi.h>
>  #include <linux/arch_topology.h>
>  #include <linux/module.h>
>  #include <linux/init.h>
> @@ -70,6 +71,73 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
>  	}
>  }
>  
> +#ifdef CONFIG_ACPI
> +static unsigned int cpu_count = 1;
> +
> +static int __init
> +acpi_parse_rintc(union acpi_subtable_headers *header,
> +			     const unsigned long end)

This all fits on one line. And also avoids the checkpatch complaint from
what you have currently done...

> +{
> +	unsigned long hart;
> +	bool found_boot_cpu = false;
> +
> +	struct acpi_madt_rintc *processor;
> +
> +	processor = (struct acpi_madt_rintc *)header;

Why not combine the above two lines?

> +	/* RINTC entry which has !ACPI_MADT_ENABLED is not enabled so skip */

This comment is a bit -ENOPARSE. Please reword it in a way that is
understandable to mere mortals like myself.

> +	if (!(processor->flags & ACPI_MADT_ENABLED))
> +		return 0;
> +
> +	hart = processor->hart_id;
> +	if (hart < 0)
> +		return 0;

Newline here please

> +	if (hart == cpuid_to_hartid_map(0)) {
> +		BUG_ON(found_boot_cpu);
> +		found_boot_cpu = 1;

This is a bool, why not assign a bool value to it so it looks more
intentional? I know this is copied from the dt code, but that should
really be on too IMO.

> +		early_map_cpu_to_node(0, acpi_numa_get_nid(cpu_count));
> +		return 0;
> +	}

And a newline here too...

> +	if (cpu_count >= NR_CPUS) {
> +		pr_warn("Invalid cpuid [%d] for hartid [%lu]\n",
> +			cpu_count, hart);
> +		return 0;
> +	}
> +
> +	cpuid_to_hartid_map(cpu_count) = hart;
> +	early_map_cpu_to_node(cpu_count, acpi_numa_get_nid(cpu_count));
> +	cpu_count++;

...and also here please!

> +	return 0;
> +}
> +
> +static void __init acpi_parse_and_init_cpus(void)
> +{
> +	int cpuid;
> +
> +	cpu_set_ops(0);

While I'm at it suggesting newline additions, adding them before
comments would be great too.

> +	/*
> +	 * do a walk of MADT to determine how many CPUs
> +	 * we have including disabled CPUs, and get information
> +	 * we need for SMP init.
> +	 */
> +	acpi_table_parse_madt(ACPI_MADT_TYPE_RINTC,
> +				      acpi_parse_rintc, 0);
> +
> +	/*
> +	 * NUMA - TODO
> +	 */

TODO before merging, or TODO at some indeterminate point in the future?

Anyways, this is all nits & this largely seem to resemble the dt code,
so with the nits fixed (and an s/ACPI: // in $subject):
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>

Cheers,
Conor.

> +	for (cpuid = 1; cpuid < nr_cpu_ids; cpuid++) {
> +		if (cpuid_to_hartid_map(cpuid) != INVALID_HARTID) {
> +			cpu_set_ops(cpuid);
> +			set_cpu_possible(cpuid, true);
> +		}
> +	}
> +}
> +#else
> +#define acpi_parse_and_init_cpus(...)	do { } while (0)
> +#endif
> +
>  static void __init of_parse_and_init_cpus(void)
>  {
>  	struct device_node *dn;
> @@ -118,7 +186,10 @@ static void __init of_parse_and_init_cpus(void)
>  
>  void __init setup_smp(void)
>  {
> -	of_parse_and_init_cpus();
> +	if (acpi_disabled)
> +		of_parse_and_init_cpus();
> +	else
> +		acpi_parse_and_init_cpus();
>  }
>  
>  static int start_secondary_cpu(int cpu, struct task_struct *tidle)
> -- 
> 2.38.0
> 
> 
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