[PATCH v6 1/3] cpufreq/amd-pstate: Fix EPP return type and handle errors during initialization

[Marco Scardovi <scardracs@disroot.org>]

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>
---
 drivers/cpufreq/amd-pstate.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index afb040c04f38..a04ff2bad4dd 100644
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -199,7 +199,7 @@ static inline int get_mode_idx_from_str(const char *str, size_t size)
 
 static DEFINE_MUTEX(amd_pstate_driver_lock);
 
-static u8 msr_get_epp(struct amd_cpudata *cpudata)
+static int msr_get_epp(struct amd_cpudata *cpudata)
 {
 	u64 value;
 	int ret;
@@ -215,12 +215,12 @@ static u8 msr_get_epp(struct amd_cpudata *cpudata)
 
 DEFINE_STATIC_CALL(amd_pstate_get_epp, msr_get_epp);
 
-static inline s16 amd_pstate_get_epp(struct amd_cpudata *cpudata)
+static inline int amd_pstate_get_epp(struct amd_cpudata *cpudata)
 {
 	return static_call(amd_pstate_get_epp)(cpudata);
 }
 
-static u8 shmem_get_epp(struct amd_cpudata *cpudata)
+static int shmem_get_epp(struct amd_cpudata *cpudata)
 {
 	u64 epp;
 	int ret;
@@ -1877,6 +1877,7 @@ static int amd_pstate_epp_cpu_init(struct cpufreq_policy *policy)
 	struct amd_cpudata *cpudata;
 	union perf_cached perf;
 	struct device *dev;
+	int default_epp;
 	int ret;
 
 	/*
@@ -1926,6 +1927,13 @@ static int amd_pstate_epp_cpu_init(struct cpufreq_policy *policy)
 
 	policy->boost_supported = READ_ONCE(cpudata->boost_supported);
 
+	/* Fetch the firmware programmed default EPP value */
+	default_epp = amd_pstate_get_epp(cpudata);
+	if (default_epp < 0) {
+		ret = default_epp;
+		goto free_cpudata1;
+	}
+
 	/*
 	 * Set the policy to provide a valid fallback value in case
 	 * the default cpufreq governor is neither powersave nor performance.
@@ -1933,7 +1941,7 @@ static int amd_pstate_epp_cpu_init(struct cpufreq_policy *policy)
 	if (amd_pstate_acpi_pm_profile_server() ||
 	    amd_pstate_acpi_pm_profile_undefined()) {
 		policy->policy = CPUFREQ_POLICY_PERFORMANCE;
-		cpudata->epp_default_ac = cpudata->epp_default_dc = amd_pstate_get_epp(cpudata);
+		cpudata->epp_default_ac = cpudata->epp_default_dc = default_epp;
 		cpudata->current_profile = PLATFORM_PROFILE_PERFORMANCE;
 	} else {
 		policy->policy = CPUFREQ_POLICY_POWERSAVE;
-- 
2.54.0