ACPI: CPPC: Avoid locking standalone full-width registers

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cpc_write() serializes every SystemMemory write with the per-CPU
rmw_lock. The lock is required for read-modify-write fields and for
registers whose access units overlap, but not for a full-width register
in a standalone access unit.

The _CPC layout is immutable after it has been parsed. Classify each
SystemMemory register at probe time and retain locking for partial
fields, invalid access widths, and overlapping access units. Allow
standalone full-width registers to bypass the descriptor lookup and
spinlock.

Store the classification in existing structure padding so that struct
cpc_register_resource does not grow.

Signed-off-by: Christian Loehle <christian.loehle@arm.com>
Link: https://patch.msgid.link/20260803210527.1285229-3-christian.loehle@arm.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

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Christian Loehle 2026-08-03 22:05:26 +01:00 • committed by Rafael J. Wysocki

parent 9d9157ee90

commit 9c5ab33a6d

2 changed files with 88 additions and 14 deletions

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97

drivers/acpi/cppc_acpi.c

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5

include/acpi/cppc_acpi.h

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