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From:   Sumit Semwal <sumit.semwal@linaro.org>
To:     agross@kernel.org, bjorn.andersson@linaro.org, lgirdwood@gmail.com,
        broonie@kernel.org, robh+dt@kernel.org
Cc:     nishakumari@codeaurora.org, linux-arm-msm@vger.kernel.org,
        linux-kernel@vger.kernel.org, devicetree@vger.kernel.org,
        kgunda@codeaurora.org, rnayak@codeaurora.org,
        Sumit Semwal <sumit.semwal@linaro.org>
Subject: [PATCH v4 1/5] regulator: Allow regulators to verify enabled during enable()
Date:   Tue,  2 Jun 2020 15:39:20 +0530
Message-Id: <20200602100924.26256-2-sumit.semwal@linaro.org>
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Some regulators might need to verify that they have indeed been enabled
after the enable() call is made and enable_time delay has passed.

This is implemented by repeatedly checking is_enabled() upto
poll_enabled_time, waiting for the already calculated enable delay in
each iteration.

Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org>
--
v2: Address review comments, including swapping enable_time and poll_enabled_time.
---
 drivers/regulator/core.c         | 58 +++++++++++++++++++++++++++++++-
 include/linux/regulator/driver.h |  5 +++
 2 files changed, 62 insertions(+), 1 deletion(-)

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index 7486f6e4e613..d9ab888da95f 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -2347,6 +2347,32 @@ static void _regulator_enable_delay(unsigned int delay)
 		udelay(us);
 }
 
+/* _regulator_check_status_enabled
+ *
+ * returns:
+ *          1 if status shows regulator is in enabled state
+ *          0 if not enabled state
+ *          else, error value as received from ops->get_status()
+ */
+static inline int _regulator_check_status_enabled(struct regulator_dev *rdev)
+{
+	int ret = rdev->desc->ops->get_status(rdev);
+
+	if (ret < 0) {
+		rdev_info(rdev, "get_status returned error: %d\n", ret);
+		return ret;
+	}
+
+	switch (ret) {
+	case REGULATOR_STATUS_OFF:
+	case REGULATOR_STATUS_ERROR:
+	case REGULATOR_STATUS_UNDEFINED:
+		return 0;
+	default:
+		return 1;
+	}
+}
+
 static int _regulator_do_enable(struct regulator_dev *rdev)
 {
 	int ret, delay;
@@ -2407,7 +2433,37 @@ static int _regulator_do_enable(struct regulator_dev *rdev)
 	 * together.  */
 	trace_regulator_enable_delay(rdev_get_name(rdev));
 
-	_regulator_enable_delay(delay);
+	/* If poll_enabled_time is set, poll upto the delay calculated
+	 * above, delaying poll_enabled_time uS to check if the regulator
+	 * actually got enabled.
+	 * If the regulator isn't enabled after enable_delay has
+	 * expired, return -ETIMEDOUT.
+	 */
+	if (rdev->desc->poll_enabled_time) {
+		unsigned int time_remaining = delay;
+
+		while (time_remaining > 0) {
+			_regulator_enable_delay(rdev->desc->poll_enabled_time);
+
+			if (rdev->desc->ops->get_status) {
+				ret = _regulator_check_status_enabled(rdev);
+				if (ret < 0)
+					return ret;
+				else if (ret)
+					break;
+			} else if (rdev->desc->ops->is_enabled(rdev))
+				break;
+
+			time_remaining -= rdev->desc->poll_enabled_time;
+		}
+
+		if (time_remaining <= 0) {
+			rdev_err(rdev, "Enabled check failed.\n");
+			return -ETIMEDOUT;
+		}
+	} else {
+		_regulator_enable_delay(delay);
+	}
 
 	trace_regulator_enable_complete(rdev_get_name(rdev));
 
diff --git a/include/linux/regulator/driver.h b/include/linux/regulator/driver.h
index 29d920516e0b..bb50e943010f 100644
--- a/include/linux/regulator/driver.h
+++ b/include/linux/regulator/driver.h
@@ -322,6 +322,9 @@ enum regulator_type {
  * @enable_time: Time taken for initial enable of regulator (in uS).
  * @off_on_delay: guard time (in uS), before re-enabling a regulator
  *
+ * @poll_enabled_time: Maximum time (in uS) to poll if the regulator is
+ *                          actually enabled, after enable() call
+ *
  * @of_map_mode: Maps a hardware mode defined in a DeviceTree to a standard mode
  */
 struct regulator_desc {
@@ -389,6 +392,8 @@ struct regulator_desc {
 
 	unsigned int off_on_delay;
 
+	unsigned int poll_enabled_time;
+
 	unsigned int (*of_map_mode)(unsigned int mode);
 };
 
-- 
2.26.2