linux-kernel - [PATCH] e_powersaver: Underclock checks

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Date:	Tue, 12 Jul 2011 00:15:16 +0100
From:	Rafał Bilski <rafalbilski@...eria.pl>
To:	Axel Lin <axel.lin@...il.com>
CC:	linux-kernel@...r.kernel.org, Dave Jones <davej@...hat.com>,
	cpufreq@...r.kernel.org
Subject: [PATCH] e_powersaver: Underclock checks

Some systems are using 1.2GHz@...mV processors running at 600MHz@...mV.
Try to detect such systems and don't touch anything on it. If CPU 
doesn't have
P-States in BIOS it will run on maximum frequency anyway.
Allow user to bypass checks by means of two new options.
Don't set frequency to maximum on module unloading to avoid bada boom.

Code totally untested as I have abadoned Centaur for Intel Atom two 
years ago.

Signed-off-by: Rafał Bilski <rafalbilski@...eria.pl>
---
  drivers/cpufreq/e_powersaver.c |   42 
+++++++++++++++++++++++++++++----------
  1 files changed, 31 insertions(+), 11 deletions(-)

diff --git a/drivers/cpufreq/e_powersaver.c b/drivers/cpufreq/e_powersaver.c
index 7883ffa..2e28af2 100644
--- a/drivers/cpufreq/e_powersaver.c
+++ b/drivers/cpufreq/e_powersaver.c
@@ -32,6 +32,10 @@ struct eps_cpu_data {

  static struct eps_cpu_data *eps_cpu[NR_CPUS];

+/* Module parameters */
+static int freq_failsafe_off;
+static int voltage_failsafe_off;
+

  static unsigned int eps_get(unsigned int cpu)
  {
@@ -253,9 +257,28 @@ static int eps_cpu_init(struct cpufreq_policy *policy)
          return -EINVAL;
      if (current_voltage > 0x1f || max_voltage > 0x1f)
          return -EINVAL;
-    if (max_voltage < min_voltage)
+    if (max_voltage < min_voltage || current_voltage < min_voltage)
          return -EINVAL;

+    /* Check for systems using underclocked CPU */
+    if (!freq_failsafe_off && max_multiplier != current_multiplier) {
+        printk(KERN_INFO "eps: Your processor is running at different 
then "
+            "its maximum frequency.\n");
+        printk(KERN_INFO "eps: Some systems use underclocked CPU's\n");
+        printk(KERN_INFO "eps: Use of \"e_powersaver\" on them may cause "
+            "irreperable damage.\n");
+        printk(KERN_INFO "eps: You can use freq_failsafe_off option to 
disable "
+            "this check.\n");
+        return -EINVAL;
+    }
+    if (!voltage_failsafe_off && max_voltage != current_voltage) {
+        printk(KERN_INFO "eps: Your processor is running at different 
then "
+            "its maximum voltage.\n");
+        printk(KERN_INFO "eps: You can use voltage_failsafe_off option 
to disable "
+            "this check.\n");
+        return -EINVAL;
+    }
+
      /* Calc FSB speed */
      fsb = cpu_khz / current_multiplier;
      /* Calc number of p-states supported */
@@ -312,17 +335,7 @@ static int eps_cpu_init(struct cpufreq_policy *policy)
  static int eps_cpu_exit(struct cpufreq_policy *policy)
  {
      unsigned int cpu = policy->cpu;
-    struct eps_cpu_data *centaur;
-    u32 lo, hi;
-
-    if (eps_cpu[cpu] == NULL)
-        return -ENODEV;
-    centaur = eps_cpu[cpu];

-    /* Get max frequency */
-    rdmsr(MSR_IA32_PERF_STATUS, lo, hi);
-    /* Set max frequency */
-    eps_set_state(centaur, cpu, hi & 0xffff);
      /* Bye */
      cpufreq_frequency_table_put_attr(policy->cpu);
      kfree(eps_cpu[cpu]);
@@ -368,6 +381,13 @@ static void __exit eps_exit(void)
      cpufreq_unregister_driver(&eps_driver);
  }

+/* Allow user to overclock his machine or to change frequency to higher 
after
+ * unloading module */
+module_param(freq_failsafe_off, int, 0644);
+MODULE_PARM_DESC(freq_failsafe_off, "Disable current vs max frequency 
check");
+module_param(voltage_failsafe_off, int, 0644);
+MODULE_PARM_DESC(voltage_failsafe_off, "Disable current vs max voltage 
check");
+
  MODULE_AUTHOR("Rafal Bilski <rafalbilski@...eria.pl>");
  MODULE_DESCRIPTION("Enhanced PowerSaver driver for VIA C7 CPU's.");
  MODULE_LICENSE("GPL");
-- 
1.7.6



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