linux-kernel - [PATCH 01/11] cpufreq: amd-pstate: optimiza the initial frequency values verification

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Date: Tue, 7 May 2024 15:15:17 +0800
From: Perry Yuan <perry.yuan@....com>
To: <rafael.j.wysocki@...el.com>, <Mario.Limonciello@....com>,
	<viresh.kumar@...aro.org>, <Ray.Huang@....com>, <gautham.shenoy@....com>,
	<Borislav.Petkov@....com>
CC: <Alexander.Deucher@....com>, <Xinmei.Huang@....com>,
	<Xiaojian.Du@....com>, <Li.Meng@....com>, <linux-pm@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: [PATCH 01/11] cpufreq: amd-pstate: optimiza the initial frequency values verification

To enhance the debugging capability of the driver loading failure for
broken CPPC ACPI tables, we can optimize the expression by moving the
verification of `min_freq`, `nominal_freq`, and other dependency values
to the `amd_pstate_init_freq()` function where they are initialized.
If any of these values are incorrect, the `amd-pstate` driver will not be registered.

By ensuring that these values are correct before they are used, it will facilitate
the debugging process when encountering driver loading failures due to faulty CPPC
ACPI tables from BIOS

Signed-off-by: Perry Yuan <perry.yuan@....com>
---
 drivers/cpufreq/amd-pstate.c | 35 ++++++++++++++++++-----------------
 1 file changed, 18 insertions(+), 17 deletions(-)

diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index 2db095867d03..be7f2d3c86b6 100644
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -873,6 +873,24 @@ static int amd_pstate_init_freq(struct amd_cpudata *cpudata)
 	WRITE_ONCE(cpudata->nominal_freq, nominal_freq);
 	WRITE_ONCE(cpudata->max_freq, max_freq);
 
+	/**
+	 * Below values need to be initialized correctly, otherwise driver will be failed to load
+	 * max_freq is calculated accoreding to (nominal_freq * highest_perf)/nominal_perf
+	 * lowest_nonlinear_freq is a value between [min_freq, nominal_freq]
+	 * Check _CPC in ACPI table ojbects if any values are incorrect
+	 */
+	if (min_freq <= 0 || max_freq <= 0 || nominal_freq <= 0 || min_freq > max_freq) {
+		pr_err("min_freq(%d) or max_freq(%d) or nominal_freq(%d) value is incorrect\n",
+			min_freq, max_freq, nominal_freq);
+		return -EINVAL;
+	}
+
+	if (lowest_nonlinear_freq <= min_freq || lowest_nonlinear_freq > nominal_freq * 1000) {
+		pr_err("lowest_nonlinear_freq(%d) value is out of range [min_freq(%d), nominal_freq(%d)]\n",
+			lowest_nonlinear_freq, min_freq, nominal_freq * 1000);
+		return -EINVAL;
+	}
+
 	return 0;
 }
 
@@ -911,15 +929,6 @@ static int amd_pstate_cpu_init(struct cpufreq_policy *policy)
 	max_freq = READ_ONCE(cpudata->max_freq);
 	nominal_freq = READ_ONCE(cpudata->nominal_freq);
 
-	if (min_freq <= 0 || max_freq <= 0 ||
-	    nominal_freq <= 0 || min_freq > max_freq) {
-		dev_err(dev,
-			"min_freq(%d) or max_freq(%d) or nominal_freq (%d) value is incorrect, check _CPC in ACPI tables\n",
-			min_freq, max_freq, nominal_freq);
-		ret = -EINVAL;
-		goto free_cpudata1;
-	}
-
 	policy->cpuinfo.transition_latency = amd_pstate_get_transition_latency(policy->cpu);
 	policy->transition_delay_us = amd_pstate_get_transition_delay_us(policy->cpu);
 
@@ -1372,14 +1381,6 @@ static int amd_pstate_epp_cpu_init(struct cpufreq_policy *policy)
 	min_freq = READ_ONCE(cpudata->min_freq);
 	max_freq = READ_ONCE(cpudata->max_freq);
 	nominal_freq = READ_ONCE(cpudata->nominal_freq);
-	if (min_freq <= 0 || max_freq <= 0 ||
-	    nominal_freq <= 0 || min_freq > max_freq) {
-		dev_err(dev,
-			"min_freq(%d) or max_freq(%d) or nominal_freq(%d) value is incorrect, check _CPC in ACPI tables\n",
-			min_freq, max_freq, nominal_freq);
-		ret = -EINVAL;
-		goto free_cpudata1;
-	}
 
 	policy->cpuinfo.min_freq = min_freq;
 	policy->cpuinfo.max_freq = max_freq;
-- 
2.34.1