Commit 56855a99 authored by Jeremy Linton's avatar Jeremy Linton Committed by Will Deacon
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ACPI/PPTT: Add function to return ACPI 6.3 Identical tokens 



ACPI 6.3 adds a flag to indicate that child nodes are all
identical cores. This is useful to authoritatively determine
if a set of (possibly offline) cores are identical or not.

Since the flag doesn't give us a unique id we can generate
one and use it to create bitmaps of sibling nodes, or simply
in a loop to determine if a subset of cores are identical.

Acked-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: default avatarHanjun Guo <hanjun.guo@linaro.org>
Reviewed-by: default avatarSudeep Holla <sudeep.holla@arm.com>
Signed-off-by: default avatarJeremy Linton <jeremy.linton@arm.com>
Signed-off-by: default avatarWill Deacon <will@kernel.org>
parent ed2b664f

drivers/acpi/pptt.c

+26 −0
Original line number Diff line number Diff line
@@ -683,3 +683,29 @@ int find_acpi_cpu_topology_package(unsigned int cpu) 
	return find_acpi_cpu_topology_tag(cpu, PPTT_ABORT_PACKAGE,

					  ACPI_PPTT_PHYSICAL_PACKAGE);

}



/**

 * find_acpi_cpu_topology_hetero_id() - Get a core architecture tag

 * @cpu: Kernel logical CPU number

 *

 * Determine a unique heterogeneous tag for the given CPU. CPUs with the same

 * implementation should have matching tags.

 *

 * The returned tag can be used to group peers with identical implementation.

 *

 * The search terminates when a level is found with the identical implementation

 * flag set or we reach a root node.

 *

 * Due to limitations in the PPTT data structure, there may be rare situations

 * where two cores in a heterogeneous machine may be identical, but won't have

 * the same tag.

 *

 * Return: -ENOENT if the PPTT doesn't exist, or the CPU cannot be found.

 * Otherwise returns a value which represents a group of identical cores

 * similar to this CPU.

 */

int find_acpi_cpu_topology_hetero_id(unsigned int cpu)

{

	return find_acpi_cpu_topology_tag(cpu, PPTT_ABORT_PACKAGE,

					  ACPI_PPTT_ACPI_IDENTICAL);

}

include/linux/acpi.h

+5 −0
Original line number Diff line number Diff line
@@ -1303,6 +1303,7 @@ static inline int lpit_read_residency_count_address(u64 *address) 
#ifdef CONFIG_ACPI_PPTT

int find_acpi_cpu_topology(unsigned int cpu, int level);

int find_acpi_cpu_topology_package(unsigned int cpu);

int find_acpi_cpu_topology_hetero_id(unsigned int cpu);

int find_acpi_cpu_cache_topology(unsigned int cpu, int level);

#else

static inline int find_acpi_cpu_topology(unsigned int cpu, int level)
@@ -1313,6 +1314,10 @@ static inline int find_acpi_cpu_topology_package(unsigned int cpu) 
{

	return -EINVAL;

}

static inline int find_acpi_cpu_topology_hetero_id(unsigned int cpu)

{

	return -EINVAL;

}

static inline int find_acpi_cpu_cache_topology(unsigned int cpu, int level)

{

	return -EINVAL;

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