regulator: vctrl-regulator: Avoid deadlock getting and setting the voltage

`cat /sys/kernel/debug/regulator/regulator_summary` ends on a deadlock
when you have a voltage controlled regulator (vctrl).

The problem is that the vctrl_get_voltage() and vctrl_set_voltage() calls the
regulator_get_voltage() and regulator_set_voltage() and that will try to lock
again the dependent regulators (the regulator supplying the control voltage).

Fix the issue by exporting the unlocked version of the regulator_get_voltage()
and regulator_set_voltage() API so drivers that need it, like the voltage
controlled regulator driver can use it.

Fixes: f8702f9e ("regulator: core: Use ww_mutex for regulators locking")
Reported-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Link: https://lore.kernel.org/r/20200116094543.2847321-1-enric.balletbo@collabora.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/regulator/core.c

@@ -3466,6 +3466,7 @@ int regulator_set_voltage_rdev(struct regulator_dev *rdev, int min_uV,
 out:
 	return ret;
 }
+EXPORT_SYMBOL(regulator_set_voltage_rdev);
 
 static int regulator_limit_voltage_step(struct regulator_dev *rdev,
 					int *current_uV, int *min_uV)
@@ -4030,6 +4031,7 @@ int regulator_get_voltage_rdev(struct regulator_dev *rdev)
 		return ret;
 	return ret - rdev->constraints->uV_offset;
 }
+EXPORT_SYMBOL(regulator_get_voltage_rdev);
 
 /**
  * regulator_get_voltage - get regulator output voltage

drivers/regulator/vctrl-regulator.c

@@ -11,10 +11,13 @@
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/of_device.h>
+#include <linux/regulator/coupler.h>
 #include <linux/regulator/driver.h>
 #include <linux/regulator/of_regulator.h>
 #include <linux/sort.h>
 
+#include "internal.h"
+
 struct vctrl_voltage_range {
 	int min_uV;
 	int max_uV;
@@ -79,7 +82,7 @@ static int vctrl_calc_output_voltage(struct vctrl_data *vctrl, int ctrl_uV)
 static int vctrl_get_voltage(struct regulator_dev *rdev)
 {
 	struct vctrl_data *vctrl = rdev_get_drvdata(rdev);
-	int ctrl_uV = regulator_get_voltage(vctrl->ctrl_reg);
+	int ctrl_uV = regulator_get_voltage_rdev(vctrl->ctrl_reg->rdev);
 
 	return vctrl_calc_output_voltage(vctrl, ctrl_uV);
 }
@@ -90,16 +93,16 @@ static int vctrl_set_voltage(struct regulator_dev *rdev,
 {
 	struct vctrl_data *vctrl = rdev_get_drvdata(rdev);
 	struct regulator *ctrl_reg = vctrl->ctrl_reg;
-	int orig_ctrl_uV = regulator_get_voltage(ctrl_reg);
+	int orig_ctrl_uV = regulator_get_voltage_rdev(ctrl_reg->rdev);
 	int uV = vctrl_calc_output_voltage(vctrl, orig_ctrl_uV);
 	int ret;
 
 	if (req_min_uV >= uV || !vctrl->ovp_threshold)
 		/* voltage rising or no OVP */
-		return regulator_set_voltage(
-			ctrl_reg,
+		return regulator_set_voltage_rdev(ctrl_reg->rdev,
 			vctrl_calc_ctrl_voltage(vctrl, req_min_uV),
-			vctrl_calc_ctrl_voltage(vctrl, req_max_uV));
+			vctrl_calc_ctrl_voltage(vctrl, req_max_uV),
+			PM_SUSPEND_ON);
 
 	while (uV > req_min_uV) {
 		int max_drop_uV = (uV * vctrl->ovp_threshold) / 100;
@@ -114,9 +117,10 @@ static int vctrl_set_voltage(struct regulator_dev *rdev,
 		next_uV = max_t(int, req_min_uV, uV - max_drop_uV);
 		next_ctrl_uV = vctrl_calc_ctrl_voltage(vctrl, next_uV);
 
-		ret = regulator_set_voltage(ctrl_reg,
+		ret = regulator_set_voltage_rdev(ctrl_reg->rdev,
+					    next_ctrl_uV,
 					    next_ctrl_uV,
-					    next_ctrl_uV);
+					    PM_SUSPEND_ON);
 		if (ret)
 			goto err;
 
@@ -130,7 +134,8 @@ static int vctrl_set_voltage(struct regulator_dev *rdev,
 
 err:
 	/* Try to go back to original voltage */
-	regulator_set_voltage(ctrl_reg, orig_ctrl_uV, orig_ctrl_uV);
+	regulator_set_voltage_rdev(ctrl_reg->rdev, orig_ctrl_uV, orig_ctrl_uV,
+				   PM_SUSPEND_ON);
 
 	return ret;
 }
@@ -155,9 +160,10 @@ static int vctrl_set_voltage_sel(struct regulator_dev *rdev,
 
 	if (selector >= vctrl->sel || !vctrl->ovp_threshold) {
 		/* voltage rising or no OVP */
-		ret = regulator_set_voltage(ctrl_reg,
+		ret = regulator_set_voltage_rdev(ctrl_reg->rdev,
+					    vctrl->vtable[selector].ctrl,
 					    vctrl->vtable[selector].ctrl,
-					    vctrl->vtable[selector].ctrl);
+					    PM_SUSPEND_ON);
 		if (!ret)
 			vctrl->sel = selector;
 
@@ -173,9 +179,10 @@ static int vctrl_set_voltage_sel(struct regulator_dev *rdev,
 		else
 			next_sel = vctrl->vtable[vctrl->sel].ovp_min_sel;
 
-		ret = regulator_set_voltage(ctrl_reg,
+		ret = regulator_set_voltage_rdev(ctrl_reg->rdev,
 					    vctrl->vtable[next_sel].ctrl,
-					    vctrl->vtable[next_sel].ctrl);
+					    vctrl->vtable[next_sel].ctrl,
+					    PM_SUSPEND_ON);
 		if (ret) {
 			dev_err(&rdev->dev,
 				"failed to set control voltage to %duV\n",
@@ -195,9 +202,10 @@ static int vctrl_set_voltage_sel(struct regulator_dev *rdev,
 err:
 	if (vctrl->sel != orig_sel) {
 		/* Try to go back to original voltage */
-		if (!regulator_set_voltage(ctrl_reg,
+		if (!regulator_set_voltage_rdev(ctrl_reg->rdev,
+					   vctrl->vtable[orig_sel].ctrl,
 					   vctrl->vtable[orig_sel].ctrl,
-					   vctrl->vtable[orig_sel].ctrl))
+					   PM_SUSPEND_ON))
 			vctrl->sel = orig_sel;
 		else
 			dev_warn(&rdev->dev,
@@ -482,7 +490,7 @@ static int vctrl_probe(struct platform_device *pdev)
 		if (ret)
 			return ret;
 
-		ctrl_uV = regulator_get_voltage(vctrl->ctrl_reg);
+		ctrl_uV = regulator_get_voltage_rdev(vctrl->ctrl_reg->rdev);
 		if (ctrl_uV < 0) {
 			dev_err(&pdev->dev, "failed to get control voltage\n");
 			return ctrl_uV;