cpufreq/amd-pstate: Fix EPP return type and handle errors during initialization

Currently, the EPP getter helper functions (msr_get_epp, shmem_get_epp, and
the static call wrapper amd_pstate_get_epp) return u8 or s16. This makes it
difficult to correctly propagate negative error values returned by the
underlying MSR read or CPPC helpers (such as rdmsrq_on_cpu or
cppc_get_epp_perf).

Modify the return type of these functions to int, allowing them to return
negative error codes properly.

Additionally, in amd_pstate_epp_cpu_init(), fetch the firmware-programmed
default EPP value and validate it before assigning it to the EPP variables.
If amd_pstate_get_epp() returns an error code, propagate the error and abort
the CPU initialization to prevent subsequent configuration failures.

Fixes: 555bbe67a622 ("cpufreq/amd-pstate: Convert all perf values to u8")
Assisted-by: Antigravity:gemini-3.5-flash
Reviewed-by: K Prateek Nayak <kprateek.nayak@amd.com>
Tested-by: K Prateek Nayak <kprateek.nayak@amd.com>
Signed-off-by: Marco Scardovi <scardracs@disroot.org>
Reviewed-by: K Prateek Nayak <kprateek.anayk@amd.com>
Link: https://lore.kernel.org/r/20260609073042.81275-2-scardracs@disroot.org
Signed-off-by: Mario Limonciello <superm1@kernel.org>

0 files changed, 0 insertions, 0 deletions