ACPI 6.2, Section 6.2.11.2 permits _CPC registers to use flexible
address spaces. Linux advertises that capability through _OSC and parses
the address space of each _CPC register independently. A directly
accessible DESIRED_PERF combined with PCC-backed limits is therefore a
valid configuration.
cppc_allow_fast_switch() only checks DESIRED_PERF, although the fast-switch
callback passes DESIRED_PERF, MIN_PERF and MAX_PERF to cppc_set_perf(). If
a limit uses PCC, that function can sleep while called from scheduler
context.
Allow fast switching only when every supported control used by the
callback has an address space already accepted for fast access. Check the
complete policy domain, including initialized CPUs that are currently
offline and may later become the policy's managing CPU.
Fixes: 658fa7b1c4 ("ACPI: CPPC: Add cppc_get_perf() API to read performance controls")
Cc: stable@vger.kernel.org
Signed-off-by: Christian Loehle <christian.loehle@arm.com>
Link: https://patch.msgid.link/20260722093825.1030594-2-christian.loehle@arm.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
11055a46f3