[PATCH] cpufreq: intel_pstate: Improve warning message on HWP-disabled hybrid CPUs

[Yohei Kojima]

Improve warning message on HWP-disabled hybrid processors to state that
intel_pstate requires HWP to be enabled on such processors [1].
Previously it warned that "intel_pstate: CPU model not supported", but
it was misleading.

[1]: https://docs.kernel.org/admin-guide/pm/intel_pstate.html

Signed-off-by: Yohei Kojima <yohei.kojima@xxxxxxxx>
---
I tested this patch on my PC equipped with i7-14700. Please note that
you need hybrid processors (i.e. Alder Lake and later) to test this.

After this patch, you will see the improved warning message if you
disable hardware P-state in your BIOS,

$ sudo dmesg -k | grep intel_pstate
[    0.478616] intel_pstate: HWP-disabled hybrid CPU is not supported

whereas this driver works as before if HWP is enabled.

$ sudo dmesg -k | grep intel_pstate
[    0.471387] intel_pstate: HWP enabled by BIOS
[    0.471388] intel_pstate: Intel P-state driver initializing
[    0.472593] intel_pstate: HWP enabled
---
 drivers/cpufreq/intel_pstate.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index 11c58af41900..99cac95537b5 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -3823,6 +3823,12 @@ static int __init intel_pstate_init(void)
 		if (no_load)
 			return -ENODEV;
 
+		id = x86_match_cpu(intel_hybrid_scaling_factor);
+		if (id) {
+			pr_info("HWP-disabled hybrid CPU is not supported\n");
+			return -ENODEV;
+		}
+
 		id = x86_match_cpu(intel_pstate_cpu_ids);
 		if (!id) {
 			pr_info("CPU model not supported\n");
-- 
2.43.0