cpufreq/amd-pstate: Do not attempt to clear MSR_AMD_CPPC_ENABLE

MSR_AMD_CPPC_ENABLE is a write once register, i.e. attempting to clear
it is futile, it will not take effect. Hence, return if disable (0)
argument is passed to the msr_cppc_enable()

Signed-off-by: Dhananjay Ugwekar <[email protected]>
Reviewed-by: Mario Limonciello <[email protected]>
Reviewed-by: Gautham R. Shenoy <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Mario Limonciello <[email protected]>

Author: dhananjay-AMD

drivers/cpufreq/amd-pstate.c

@@ -311,6 +311,12 @@ static inline int msr_cppc_enable(bool enable)
 	int ret, cpu;
 	unsigned long logical_proc_id_mask = 0;
 
+       /*
+        * MSR_AMD_CPPC_ENABLE is write-once, once set it cannot be cleared.
+        */
+	if (!enable)
+		return 0;
+
 	if (enable == cppc_enabled)
 		return 0;