Re: [PATCH 1/2] ACPI/PPTT: Add support for ACPI 6.3 thread flag

[Sudeep Holla <sudeep.holla@arm.com>]

On Thu, May 23, 2019 at 05:40:14PM -0500, Jeremy Linton wrote:
> ACPI 6.3 adds a flag to the CPU node to indicate whether
> the given PE is a thread. Add a function to return that
> information for a given linux logical CPU.
> 
> Signed-off-by: Jeremy Linton <jeremy.linton@arm.com>
> ---
>  drivers/acpi/pptt.c  | 53 +++++++++++++++++++++++++++++++++++++++++++-
>  include/linux/acpi.h |  5 +++++
>  2 files changed, 57 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/acpi/pptt.c b/drivers/acpi/pptt.c
> index b72e6afaa8fb..6f43a0c05f61 100644
> --- a/drivers/acpi/pptt.c
> +++ b/drivers/acpi/pptt.c
> @@ -517,6 +517,43 @@ static int find_acpi_cpu_topology_tag(unsigned int cpu, int level, int flag)
>  	return retval;
>  }
>  
> +/**
> + * check_acpi_cpu_flag() - Determine if CPU node has a flag set
> + * @cpu: Kernel logical CPU number
> + * @rev: The PPTT revision defining the flag
> + * @flag: The flag itself
> + *
> + * Check the node representing a CPU for a given flag.
> + *
> + * Return: -ENOENT if the PPTT doesn't exist, the CPU cannot be found or
> + *	   the table revision isn't new enough.
> + * Otherwise returns flag value
> + */
> +static int check_acpi_cpu_flag(unsigned int cpu, int rev, u32 flag)

Initially, I thought we already have similar function, but I was wrong.

> +{
> +	struct acpi_table_header *table;
> +	acpi_status status;
> +	u32 acpi_cpu_id = get_acpi_id_for_cpu(cpu);
> +	struct acpi_pptt_processor *cpu_node = NULL;
> +	int ret = -ENONET;


Unfortunately even ENONET is defined and will silently compile fine, but
I assume you need ENOENT as mentioned in the comment/doc.
> +
> +	status = acpi_get_table(ACPI_SIG_PPTT, 0, &table);
> +	if (ACPI_FAILURE(status)) {
> +		acpi_pptt_warn_missing();
> +		return ret;
> +	}
> +
> +	if (table->revision >= rev)
> +		cpu_node = acpi_find_processor_node(table, acpi_cpu_id);
> +
> +	if (cpu_node)
> +		ret = cpu_node->flags & flag;
> +
> +	acpi_put_table(table);
> +
> +	return ret;
> +}
> +
>  /**
>   * acpi_find_last_cache_level() - Determines the number of cache levels for a PE
>   * @cpu: Kernel logical CPU number
> @@ -581,6 +618,21 @@ int cache_setup_acpi(unsigned int cpu)
>  	return status;
>  }
>  
> +/**
> + * acpi_pptt_cpu_is_thread() - Determine if logical CPU is a thread
> + * @cpu: Kernel logical CPU number
> + *
> + *
> + * Return: 1, a thread
> + *         0, not a thread
> + *         -ENOENT if the PPTT doesn't exist, the CPU cannot be found or
> + *         the table revision isn't new enough.
> + */
> +int acpi_pptt_cpu_is_thread(unsigned int cpu)
> +{
> +	return check_acpi_cpu_flag(cpu, 2, ACPI_PPTT_ACPI_PROCESSOR_IS_THREAD);
> +}
> +
>  /**
>   * find_acpi_cpu_topology() - Determine a unique topology value for a given CPU
>   * @cpu: Kernel logical CPU number
> @@ -641,7 +693,6 @@ int find_acpi_cpu_cache_topology(unsigned int cpu, int level)
>  	return ret;
>  }
>  
> -

Spurious ?

>  /**
>   * find_acpi_cpu_topology_package() - Determine a unique CPU package value
>   * @cpu: Kernel logical CPU number
> diff --git a/include/linux/acpi.h b/include/linux/acpi.h
> index 98440df7fe42..513833233c65 100644
> --- a/include/linux/acpi.h
> +++ b/include/linux/acpi.h
> @@ -1314,10 +1314,15 @@ static inline int lpit_read_residency_count_address(u64 *address)
>  #endif
>  
>  #ifdef CONFIG_ACPI_PPTT
> +int acpi_pptt_cpu_is_thread(unsigned int cpu);
>  int find_acpi_cpu_topology(unsigned int cpu, int level);
>  int find_acpi_cpu_topology_package(unsigned int cpu);
>  int find_acpi_cpu_cache_topology(unsigned int cpu, int level);
>  #else
> +static inline int acpi_pptt_cpu_is_thread(unsigned int cpu)
> +{
> +	return -EINVAL;
> +}
>  static inline int find_acpi_cpu_topology(unsigned int cpu, int level)
>  {
>  	return -EINVAL;
> -- 
> 2.21.0
> 

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