[PATCH] regulator: implement basic reference counter

[Eugen Hristev]

Some devices share a regulator supply, when the first one will request
regulator disable, the second device will have it's supply cut off before
graciously shutting down. Hence there will be timeouts and other failed
operations.
Implement a reference counter mechanism similar with what is done in
Linux, to keep track of enable and disable requests, and only disable the
regulator when the last of the consumers has requested shutdown.

Signed-off-by: Eugen Hristev <eugen.hris...@collabora.com>
---
 drivers/power/regulator/regulator_common.c | 22 ++++++++++++++++++++++
 drivers/power/regulator/regulator_common.h |  1 +
 2 files changed, 23 insertions(+)

diff --git a/drivers/power/regulator/regulator_common.c 
b/drivers/power/regulator/regulator_common.c
index 93d8196b381e..edda25336176 100644
--- a/drivers/power/regulator/regulator_common.c
+++ b/drivers/power/regulator/regulator_common.c
@@ -73,6 +73,23 @@ int regulator_common_set_enable(const struct udevice *dev,
                return 0;
        }
 
+       /* If previously enabled, increase count */
+       if (enable && dev_pdata->enable_count > 0) {
+               dev_pdata->enable_count++;
+               return 0;
+       }
+
+       if (!enable) {
+               if (dev_pdata->enable_count > 1) {
+                       /* If enabled multiple times, decrease count */
+                       dev_pdata->enable_count--;
+                       return 0;
+               } else if (!dev_pdata->enable_count) {
+                       /* If already disabled, do nothing */
+                       return 0;
+               }
+       }
+
        ret = dm_gpio_set_value(&dev_pdata->gpio, enable);
        if (ret) {
                pr_err("Can't set regulator : %s gpio to: %d\n", dev->name,
@@ -87,5 +104,10 @@ int regulator_common_set_enable(const struct udevice *dev,
        if (!enable && dev_pdata->off_on_delay_us)
                udelay(dev_pdata->off_on_delay_us);
 
+       if (enable)
+               dev_pdata->enable_count++;
+       else
+               dev_pdata->enable_count--;
+
        return 0;
 }
diff --git a/drivers/power/regulator/regulator_common.h 
b/drivers/power/regulator/regulator_common.h
index c10492f01675..8167bc866261 100644
--- a/drivers/power/regulator/regulator_common.h
+++ b/drivers/power/regulator/regulator_common.h
@@ -13,6 +13,7 @@ struct regulator_common_plat {
        struct gpio_desc gpio; /* GPIO for regulator enable control */
        unsigned int startup_delay_us;
        unsigned int off_on_delay_us;
+       unsigned int enable_count;
 };
 
 int regulator_common_of_to_plat(struct udevice *dev,
-- 
2.34.1