acerhdf has been doing an on-off fan control using hysteresis by
post-manipulating the outcome of thermal subsystem trip point handling.
This patch enables acerhdf to use the bang-bang governor, which is
intended for on-off controlled fans.

CC: Zhang Rui <rui.zh...@intel.com>
Cc: Andreas Mohr <a...@lisas.de>
Cc: Borislav Petkov <b...@suse.de>
Signed-off-by: Peter Feuerer <pe...@piie.net>
---
 drivers/platform/x86/Kconfig   |  2 +-
 drivers/platform/x86/acerhdf.c | 48 +++++++++++++++++++++++++++++++++++-------
 2 files changed, 41 insertions(+), 9 deletions(-)

diff --git a/drivers/platform/x86/Kconfig b/drivers/platform/x86/Kconfig
index 27df2c5..0c15d89 100644
--- a/drivers/platform/x86/Kconfig
+++ b/drivers/platform/x86/Kconfig
@@ -38,7 +38,7 @@ config ACER_WMI
 
 config ACERHDF
        tristate "Acer Aspire One temperature and fan driver"
-       depends on THERMAL && ACPI
+       depends on ACPI && THERMAL_GOV_BANG_BANG
        ---help---
          This is a driver for Acer Aspire One netbooks. It allows to access
          the temperature sensor and to control the fan.
diff --git a/drivers/platform/x86/acerhdf.c b/drivers/platform/x86/acerhdf.c
index 176edbd..f3884f9 100644
--- a/drivers/platform/x86/acerhdf.c
+++ b/drivers/platform/x86/acerhdf.c
@@ -50,7 +50,7 @@
  */
 #undef START_IN_KERNEL_MODE
 
-#define DRV_VER "0.5.30"
+#define DRV_VER "0.5.31"
 
 /*
  * According to the Atom N270 datasheet,
@@ -135,8 +135,8 @@ struct bios_settings_t {
        const char *vendor;
        const char *product;
        const char *version;
-       unsigned char fanreg;
-       unsigned char tempreg;
+       u8 fanreg;
+       u8 tempreg;
        struct fancmd cmd;
        int mcmd_enable;
 };
@@ -259,6 +259,17 @@ static const struct bios_settings_t bios_tbl[] = {
 
 static const struct bios_settings_t *bios_cfg __read_mostly;
 
+/*
+ * this struct is used to instruct thermal layer to use bang_bang instead of
+ * default governor for acerhdf
+ */
+static struct thermal_zone_params acerhdf_zone_params = {
+       .governor_name = "bang_bang",
+       .no_hwmon = 0,
+       .num_tbps = 0,
+       .tbp = 0,
+};
+
 static int acerhdf_get_temp(int *temp)
 {
        u8 read_temp;
@@ -436,6 +447,17 @@ static int acerhdf_get_trip_type(struct 
thermal_zone_device *thermal, int trip,
 {
        if (trip == 0)
                *type = THERMAL_TRIP_ACTIVE;
+       if (trip == 1)
+               *type = THERMAL_TRIP_CRITICAL;
+
+       return 0;
+}
+
+static int acerhdf_get_trip_hyst(struct thermal_zone_device *thermal, int trip,
+                                unsigned long *temp)
+{
+       if (trip == 0)
+               *temp = fanon - fanoff;
 
        return 0;
 }
@@ -445,6 +467,8 @@ static int acerhdf_get_trip_temp(struct thermal_zone_device 
*thermal, int trip,
 {
        if (trip == 0)
                *temp = fanon;
+       else if (trip == 1)
+               *temp = ACERHDF_TEMP_CRIT;
 
        return 0;
 }
@@ -464,8 +488,10 @@ static struct thermal_zone_device_ops acerhdf_dev_ops = {
        .get_mode = acerhdf_get_mode,
        .set_mode = acerhdf_set_mode,
        .get_trip_type = acerhdf_get_trip_type,
+       .get_trip_hyst = acerhdf_get_trip_hyst,
        .get_trip_temp = acerhdf_get_trip_temp,
        .get_crit_temp = acerhdf_get_crit_temp,
+       .notify = NULL,
 };
 
 
@@ -516,9 +542,7 @@ static int acerhdf_set_cur_state(struct 
thermal_cooling_device *cdev,
        }
 
        if (state == 0) {
-               /* turn fan off only if below fanoff temperature */
-               if ((cur_state == ACERHDF_FAN_AUTO) &&
-                   (cur_temp < fanoff))
+               if (cur_state == ACERHDF_FAN_AUTO)
                        acerhdf_change_fanstate(ACERHDF_FAN_OFF);
        } else {
                if (cur_state == ACERHDF_FAN_OFF)
@@ -696,12 +720,20 @@ static int acerhdf_register_thermal(void)
        if (IS_ERR(cl_dev))
                return -EINVAL;
 
-       thz_dev = thermal_zone_device_register("acerhdf", 1, 0, NULL,
-                                             &acerhdf_dev_ops, NULL, 0,
+       thz_dev = thermal_zone_device_register("acerhdf", 2, 0, NULL,
+                                             &acerhdf_dev_ops,
+                                             &acerhdf_zone_params, 0,
                                              (kernelmode) ? interval*1000 : 0);
        if (IS_ERR(thz_dev))
                return -EINVAL;
 
+       if (strcmp(thz_dev->governor->name,
+                               acerhdf_zone_params.governor_name)) {
+               pr_err("Didn't get thermal governor %s, perhaps not compiled 
into thermal subsystem.\n",
+                               acerhdf_zone_params.governor_name);
+               return -EINVAL;
+       }
+
        return 0;
 }
 
-- 
1.9.2

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