regulator: core: Support bypass mode

Many regulators support a bypass mode where they simply switch their
input supply to the output. This is mainly used in low power retention
states where power consumption is extremely low so higher voltage or
less clean supplies can be used.

Support this by providing ops for the drivers and a consumer API which
allows the device to be put into bypass mode if all consumers enable it
and the machine enables permission for this.

This is not supported as a mode since the existing modes are rarely used
due to fuzzy definition and mostly redundant with modern hardware which is
able to respond promptly to load changes.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Reviewed-by: Graeme Gregory <gg@slimlogic.co.uk>

5 files changed, 126 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-class-regulator b/Documentation/ABI/testing/sysfs-class-regulator
index e091fa873792..bc578bc60628 100644
--- a/Documentation/ABI/testing/sysfs-class-regulator
+++ b/Documentation/ABI/testing/sysfs-class-regulator
@@ -349,3 +349,24 @@ Description:
 
                 This will be one of the same strings reported by
                 the "state" attribute.
+
+What:           /sys/class/regulator/.../bypass
+Date:           September 2012
+KernelVersion:  3.7
+Contact:        Mark Brown <broonie@opensource.wolfsonmicro.com>
+Description:
+                Some regulator directories will contain a field called
+                bypass.  This indicates if the device is in bypass mode.
+
+                This will be one of the following strings:
+
+                'enabled'
+                'disabled'
+                'unknown'
+
+                'enabled' means the regulator is in bypass mode.
+
+                'disabled' means that the regulator is regulating.
+
+                'unknown' means software cannot determine the state, or
+                the reported state is invalid.
diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index 48385318175a..64e16053975e 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -77,6 +77,7 @@ struct regulator {
         struct device *dev;
         struct list_head list;
         unsigned int always_on:1;
+        unsigned int bypass:1;
         int uA_load;
         int min_uV;
         int max_uV;
@@ -394,6 +395,9 @@ static ssize_t regulator_status_show(struct device *dev,
         case REGULATOR_STATUS_STANDBY:
                 label = "standby";
                 break;
+        case REGULATOR_STATUS_BYPASS:
+                label = "bypass";
+                break;
         case REGULATOR_STATUS_UNDEFINED:
                 label = "undefined";
                 break;
@@ -585,6 +589,27 @@ static ssize_t regulator_suspend_standby_state_show(struct device *dev,
 static DEVICE_ATTR(suspend_standby_state, 0444,
                 regulator_suspend_standby_state_show, NULL);
 
+static ssize_t regulator_bypass_show(struct device *dev,
+                                     struct device_attribute *attr, char *buf)
+{
+        struct regulator_dev *rdev = dev_get_drvdata(dev);
+        const char *report;
+        bool bypass;
+        int ret;
+
+        ret = rdev->desc->ops->get_bypass(rdev, &bypass);
+
+        if (ret != 0)
+                report = "unknown";
+        else if (bypass)
+                report = "enabled";
+        else
+                report = "disabled";
+
+        return sprintf(buf, "%s\n", report);
+}
+static DEVICE_ATTR(bypass, 0444,
+                   regulator_bypass_show, NULL);
 
 /*
  * These are the only attributes are present for all regulators.
@@ -2674,6 +2699,59 @@ out:
 EXPORT_SYMBOL_GPL(regulator_set_optimum_mode);
 
 /**
+ * regulator_allow_bypass - allow the regulator to go into bypass mode
+ *
+ * @regulator: Regulator to configure
+ * @allow: enable or disable bypass mode
+ *
+ * Allow the regulator to go into bypass mode if all other consumers
+ * for the regulator also enable bypass mode and the machine
+ * constraints allow this.  Bypass mode means that the regulator is
+ * simply passing the input directly to the output with no regulation.
+ */
+int regulator_allow_bypass(struct regulator *regulator, bool enable)
+{
+        struct regulator_dev *rdev = regulator->rdev;
+        int ret = 0;
+
+        if (!rdev->desc->ops->set_bypass)
+                return 0;
+
+        if (rdev->constraints &&
+            !(rdev->constraints->valid_ops_mask & REGULATOR_CHANGE_BYPASS))
+                return 0;
+
+        mutex_lock(&rdev->mutex);
+
+        if (enable && !regulator->bypass) {
+                rdev->bypass_count++;
+
+                if (rdev->bypass_count == rdev->open_count) {
+                        ret = rdev->desc->ops->set_bypass(rdev, enable);
+                        if (ret != 0)
+                                rdev->bypass_count--;
+                }
+
+        } else if (!enable && regulator->bypass) {
+                rdev->bypass_count--;
+
+                if (rdev->bypass_count != rdev->open_count) {
+                        ret = rdev->desc->ops->set_bypass(rdev, enable);
+                        if (ret != 0)
+                                rdev->bypass_count++;
+                }
+        }
+
+        if (ret == 0)
+                regulator->bypass = enable;
+
+        mutex_unlock(&rdev->mutex);
+
+        return ret;
+}
+EXPORT_SYMBOL_GPL(regulator_allow_bypass);
+
+/**
  * regulator_register_notifier - register regulator event notifier
  * @regulator: regulator source
  * @nb: notifier block
@@ -3036,6 +3114,11 @@ static int add_regulator_attributes(struct regulator_dev *rdev)
                 if (status < 0)
                         return status;
         }
+        if (ops->get_bypass) {
+                status = device_create_file(dev, &dev_attr_bypass);
+                if (status < 0)
+                        return status;
+        }
 
         /* some attributes are type-specific */
         if (rdev->desc->type == REGULATOR_CURRENT) {
@@ -3124,6 +3207,8 @@ static void rdev_init_debugfs(struct regulator_dev *rdev)
                            &rdev->use_count);
         debugfs_create_u32("open_count", 0444, rdev->debugfs,
                            &rdev->open_count);
+        debugfs_create_u32("bypass_count", 0444, rdev->debugfs,
+                           &rdev->bypass_count);
 }
 
 /**
diff --git a/include/linux/regulator/consumer.h b/include/linux/regulator/consumer.h
index da339fd8c755..ea3e35816621 100644
--- a/include/linux/regulator/consumer.h
+++ b/include/linux/regulator/consumer.h
@@ -177,6 +177,8 @@ int regulator_set_mode(struct regulator *regulator, unsigned int mode);
 unsigned int regulator_get_mode(struct regulator *regulator);
 int regulator_set_optimum_mode(struct regulator *regulator, int load_uA);
 
+int regulator_allow_bypass(struct regulator *regulator, bool allow);
+
 /* regulator notifier block */
 int regulator_register_notifier(struct regulator *regulator,
                               struct notifier_block *nb);
@@ -328,6 +330,12 @@ static inline int regulator_set_optimum_mode(struct regulator *regulator,
         return REGULATOR_MODE_NORMAL;
 }
 
+static inline int regulator_allow_bypass(struct regulator *regulator,
+                                         bool allow)
+{
+        return 0;
+}
+
 static inline int regulator_register_notifier(struct regulator *regulator,
                               struct notifier_block *nb)
 {
diff --git a/include/linux/regulator/driver.h b/include/linux/regulator/driver.h
index bac4c871f3bd..c9869cfbf261 100644
--- a/include/linux/regulator/driver.h
+++ b/include/linux/regulator/driver.h
@@ -32,6 +32,8 @@ enum regulator_status {
         REGULATOR_STATUS_NORMAL,
         REGULATOR_STATUS_IDLE,
         REGULATOR_STATUS_STANDBY,
+        /* The regulator is enabled but not regulating */
+        REGULATOR_STATUS_BYPASS,
         /* in case that any other status doesn't apply */
         REGULATOR_STATUS_UNDEFINED,
 };
@@ -67,6 +69,9 @@ enum regulator_status {
  * @get_optimum_mode: Get the most efficient operating mode for the regulator
  *                    when running with the specified parameters.
  *
+ * @set_bypass: Set the regulator in bypass mode.
+ * @get_bypass: Get the regulator bypass mode state.
+ *
  * @enable_time: Time taken for the regulator voltage output voltage to
  *               stabilise after being enabled, in microseconds.
  * @set_ramp_delay: Set the ramp delay for the regulator. The driver should
@@ -133,6 +138,10 @@ struct regulator_ops {
         unsigned int (*get_optimum_mode) (struct regulator_dev *, int input_uV,
                                           int output_uV, int load_uA);
 
+        /* control and report on bypass mode */
+        int (*set_bypass)(struct regulator_dev *dev, bool enable);
+        int (*get_bypass)(struct regulator_dev *dev, bool *enable);
+
         /* the operations below are for configuration of regulator state when
          * its parent PMIC enters a global STANDBY/HIBERNATE state */
 
@@ -253,6 +262,7 @@ struct regulator_dev {
         int exclusive;
         u32 use_count;
         u32 open_count;
+        u32 bypass_count;
 
         /* lists we belong to */
         struct list_head list; /* list of all regulators */
diff --git a/include/linux/regulator/machine.h b/include/linux/regulator/machine.h
index 40dd0a394cfa..36adbc82de6a 100644
--- a/include/linux/regulator/machine.h
+++ b/include/linux/regulator/machine.h
@@ -32,6 +32,7 @@ struct regulator;
  *           board/machine.
  * STATUS:   Regulator can be enabled and disabled.
  * DRMS:     Dynamic Regulator Mode Switching is enabled for this regulator.
+ * BYPASS:   Regulator can be put into bypass mode
  */
 
 #define REGULATOR_CHANGE_VOLTAGE        0x1
@@ -39,6 +40,7 @@ struct regulator;
 #define REGULATOR_CHANGE_MODE           0x4
 #define REGULATOR_CHANGE_STATUS         0x8
 #define REGULATOR_CHANGE_DRMS           0x10
+#define REGULATOR_CHANGE_BYPASS         0x20
 
 /**
  * struct regulator_state - regulator state during low power system states