cpufreq/amd-pstate: Skip auto_sel write when it already matches the mode

Since commit 9dfd13f80c85 ("cpufreq/amd-pstate: Toggle auto_sel in active
mode on shared memory systems"), shmem_init_perf() programs
AUTONOMOUS_SELECTION_ENABLE unconditionally, including in active mode.

Platforms that exclusively support autonomous selection report this field
as an Integer of 1, as required by the ACPI specification, instead of as a
register descriptor.  cppc_get_reg_val() reads such a field back
successfully, but cppc_set_reg_val() rejects the write with -EOPNOTSUPP
because the entry is not an ACPI_TYPE_BUFFER.

shmem_init_perf() propagates that error, so every amd_pstate_epp_cpu_init()
fails, cpufreq_register_driver() ends up with an empty policy list and
returns -ENODEV, and amd-pstate refuses to load at all:

  amd_pstate: failed to set auto_sel, ret: -95
  amd_pstate: Failed to initialize CPU 0: -95
  ...
  amd_pstate: failed to register with return -19

Skip the write when the register already holds the value the requested mode
needs.  Active and guided mode are fixed on these platforms, which report
auto_sel as 1, while passive mode still fails to load on a platform that
cannot disable autonomous selection, exactly as it did before the
offending commit.

Fixes: 9dfd13f80c85 ("cpufreq/amd-pstate: Toggle auto_sel in active mode on shared memory systems")
Cc: stable@vger.kernel.org
Reviewed-by: K Prateek Nayak <kprateek.nayak@amd.com>
Tested-by: K Prateek Nayak <kprateek.nayak@amd.com>
Tested-by: LFRon <ronforever@outlook.com>
Signed-off-by: Wentao Guan <guanwentao@uniontech.com>
Link: https://lore.kernel.org/r/20260918090909.86544-1-guanwentao@uniontech.com
Signed-off-by: Mario Limonciello <superm1@kernel.org>

0 files changed, 0 insertions, 0 deletions