CPUFreq scaling governor interface for Linux/Android hosted devices.

For a usage example see http://gerrit.rockbox.org/r/#/c/1074/

Change-Id: I1d61e0eba6552a9b5d6e15a2e3169435b2f7079d

firmware/SOURCES

@@ -12,6 +12,7 @@ powermgmt.c
 
 #ifdef __linux__
 target/hosted/cpuinfo-linux.c
+target/hosted/cpufreq-linux.c
 #endif
 
 #if !defined(SAMSUNG_YPR0) || defined(SIMULATOR) /* uses as3514 rtc */

firmware/target/hosted/cpufreq-linux.c

@@ -0,0 +1,151 @@
+/***************************************************************************
+ *             __________               __   ___
+ *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
+ *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
+ *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
+ *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
+ *                     \/            \/     \/    \/            \/
+ *
+ * Copyright (C) 2015 by Udo Schläpfer
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ****************************************************************************/
+
+
+#include <stdio.h>
+#include <string.h>
+
+#include "config.h"
+#include "cpuinfo-linux.h"
+#include "debug.h"
+
+#include "cpufreq-linux.h"
+
+
+static FILE* open_read(const char* file_name)
+{
+    FILE *f = fopen(file_name, "r");
+    if(f == NULL)
+    {
+        DEBUGF("ERROR %s: Can not open %s for reading.", __func__, file_name);
+    }
+
+    return f;
+}
+
+
+void cpufreq_available_governors(char* governors, int governors_size, int cpu)
+{
+    if(governors_size <= 0)
+    {
+        DEBUGF("ERROR %s: Invalid governors_size: %d.", __func__, governors_size);
+        return;
+    }
+
+    if(cpu < 0)
+    {
+        DEBUGF("ERROR %s: Invalid cpu: %d.", __func__, cpu);
+        return;
+    }
+
+    char available_governors_interface[70];
+
+    snprintf(available_governors_interface,
+             sizeof(available_governors_interface),
+             "/sys/devices/system/cpu/cpu%d/cpufreq/scaling_available_governors",
+             cpu);
+
+    FILE *f = open_read(available_governors_interface);
+    if(f == NULL)
+    {
+        return;
+    }
+
+    if(fgets(governors, governors_size, f) == NULL)
+    {
+        DEBUGF("ERROR %s: Read failed for %s.", __func__, available_governors_interface);
+        fclose(f);
+        return;
+    }
+
+    DEBUGF("DEBUG %s: Available governors for cpu %d: %s.", __func__, cpu, governors);
+
+    fclose(f);
+}
+
+
+static FILE* open_write(const char* file_name)
+{
+    FILE *f = fopen(file_name, "w");
+    if(f == NULL)
+    {
+        DEBUGF("ERROR %s: Can not open %s for writing.", __func__, file_name);
+    }
+
+    return f;
+}
+
+
+static void set_governor_for_cpu(const char* governor, int cpu)
+{
+    DEBUGF("DEBUG %s: governor: %s, cpu: %d.", __func__, governor, cpu);
+
+    char scaling_governor_interface[64];
+
+    snprintf(scaling_governor_interface,
+             sizeof(scaling_governor_interface),
+             "/sys/devices/system/cpu/cpu%d/cpufreq/scaling_governor",
+             cpu);
+
+    FILE *f = open_write(scaling_governor_interface);
+    if(f == NULL)
+    {
+        return;
+    }
+
+    if(fprintf(f, "%s", governor) < 1)
+    {
+        DEBUGF("ERROR %s: Write failed for %s.", __func__, scaling_governor_interface);
+    }
+
+    fclose(f);
+}
+
+
+void cpufreq_set_governor(const char* governor, int cpu)
+{
+    if(governor == NULL)
+    {
+        DEBUGF("ERROR %s: Invalid governor.", __func__);
+        return;
+    }
+
+    if(cpu < CPUFREQ_ALL_CPUS)
+    {
+        DEBUGF("ERROR %s: Invalid cpu: %d.", __func__, cpu);
+        return;
+    }
+
+    DEBUGF("DEBUG %s: governor: %s, cpu: %d.", __func__, governor, cpu);
+
+    if(cpu == CPUFREQ_ALL_CPUS)
+    {
+        int max_cpu = cpucount_linux();
+
+        for(int count = 0; count < max_cpu; ++count)
+        {
+            set_governor_for_cpu(governor, count);
+        }
+    }
+    else
+    {
+        set_governor_for_cpu(governor, cpu);
+    }
+}

firmware/target/hosted/cpufreq-linux.h

@@ -0,0 +1,58 @@
+/***************************************************************************
+ *             __________               __   ___
+ *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
+ *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
+ *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
+ *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
+ *                     \/            \/     \/    \/            \/
+ *
+ * Copyright (C) 2015 by Udo Schläpfer
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ *
+ * Interface for the Linux CPUFreq kernel modul.
+ * See https://www.kernel.org/doc/Documentation/cpu-freq/
+ *
+ ****************************************************************************/
+
+
+#ifndef __CPUFREQ_LINUX_H__
+#define __CPUFREQ_LINUX_H__
+
+
+#include <stdbool.h>
+
+
+/*
+    Get the available governors for cpu.
+    governors Preallocated string for the available governors. On succes this will look like
+              "performance ondemand powersave", each word beeing a governor that can be used with
+              cpufreq_set_governor.
+    governors_size Size of governors.
+    cpu The cpu, starting with 0, for which to get the available governors. CPUFREQ_ALL_CPUS is not
+        supported, you must supply a cpu. See cpucount_linux in cpuinfo-linux.h.
+*/
+void cpufreq_available_governors(char* governors, int governors_size, int cpu);
+
+
+/*
+    Set the cpufreq governor for cpu.
+    governor The governor to set. This must be one of the available governors returned by
+             cpufreq_available_governors.
+    cpu The cpu, starting with 0, for which to set the governor. CPUFREQ_ALL_CPUS to set
+        the governor for all cpus. See cpucount_linux in cpuinfo-linux.h.
+*/
+void cpufreq_set_governor(const char* governor, int cpu);
+
+
+static const int CPUFREQ_ALL_CPUS = -1;
+
+
+#endif