[PATCH] pinctrl: qcom: ssbi-gpio: fix gpio-hog related boot issues

[Brian Masney <masneyb@xxxxxxxxxxxxx>]

When attempting to setup up a gpio hog, device probing will repeatedly
fail with -EPROBE_DEFERED errors. It is caused by a circular dependency
between the gpio and pinctrl frameworks. If the gpio-ranges property is
present in device tree, then the gpio framework will handle the gpio pin
registration and eliminate the circular dependency.

See Christian Lamparter's commit a86caa9ba5d7 ("pinctrl: msm: fix
gpio-hog related boot issues") for a detailed commit message that
explains the issue in much more detail. The code comment in this commit
came from Christian's commit.

I did not test this change against any hardware supported by this
particular driver, however I was able to validate this same fix works
for pinctrl-spmi-gpio.c using a LG Nexus 5 (hammerhead) phone.

Signed-off-by: Brian Masney <masneyb@xxxxxxxxxxxxx>
---
For the patch and discussion regarding pinctrl-spmi-gpio.c, see
https://lore.kernel.org/lkml/20181101001149.13453-6-masneyb@xxxxxxxxxxxxx/

 drivers/pinctrl/qcom/pinctrl-ssbi-gpio.c | 23 +++++++++++++++++------
 1 file changed, 17 insertions(+), 6 deletions(-)

diff --git a/drivers/pinctrl/qcom/pinctrl-ssbi-gpio.c b/drivers/pinctrl/qcom/pinctrl-ssbi-gpio.c
index 6b30bef829ab..ded7d765af2e 100644
--- a/drivers/pinctrl/qcom/pinctrl-ssbi-gpio.c
+++ b/drivers/pinctrl/qcom/pinctrl-ssbi-gpio.c
@@ -762,12 +762,23 @@ static int pm8xxx_gpio_probe(struct platform_device *pdev)
 		return ret;
 	}
 
-	ret = gpiochip_add_pin_range(&pctrl->chip,
-				     dev_name(pctrl->dev),
-				     0, 0, pctrl->chip.ngpio);
-	if (ret) {
-		dev_err(pctrl->dev, "failed to add pin range\n");
-		goto unregister_gpiochip;
+	/*
+	 * For DeviceTree-supported systems, the gpio core checks the
+	 * pinctrl's device node for the "gpio-ranges" property.
+	 * If it is present, it takes care of adding the pin ranges
+	 * for the driver. In this case the driver can skip ahead.
+	 *
+	 * In order to remain compatible with older, existing DeviceTree
+	 * files which don't set the "gpio-ranges" property or systems that
+	 * utilize ACPI the driver has to call gpiochip_add_pin_range().
+	 */
+	if (!of_property_read_bool(pctrl->dev->of_node, "gpio-ranges")) {
+		ret = gpiochip_add_pin_range(&pctrl->chip, dev_name(pctrl->dev),
+					     0, 0, pctrl->chip.ngpio);
+		if (ret) {
+			dev_err(pctrl->dev, "failed to add pin range\n");
+			goto unregister_gpiochip;
+		}
 	}
 
 	platform_set_drvdata(pdev, pctrl);
-- 
2.17.2