power: reset: qcom-pon: add support for pm8941-pon

For PM8941 we don't have a defined field to store the reset reason.
Support wrapping pwrkey and resin, but without writing the reset
reason.
Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

drivers/power/reset/qcom-pon.c

@@ -17,6 +17,8 @@
 #define GEN1_REASON_SHIFT		2
 #define GEN2_REASON_SHIFT		1
 
+#define NO_REASON_SHIFT			0
+
 struct pm8916_pon {
 	struct device *dev;
 	struct regmap *regmap;
@@ -45,6 +47,7 @@ static int pm8916_reboot_mode_write(struct reboot_mode_driver *reboot,
 static int pm8916_pon_probe(struct platform_device *pdev)
 {
 	struct pm8916_pon *pon;
+	long reason_shift;
 	int error;
 
 	pon = devm_kzalloc(&pdev->dev, sizeof(*pon), GFP_KERNEL);
@@ -64,13 +67,17 @@ static int pm8916_pon_probe(struct platform_device *pdev)
 	if (error)
 		return error;
 
-	pon->reboot_mode.dev = &pdev->dev;
-	pon->reason_shift = (long)of_device_get_match_data(&pdev->dev);
-	pon->reboot_mode.write = pm8916_reboot_mode_write;
-	error = devm_reboot_mode_register(&pdev->dev, &pon->reboot_mode);
-	if (error) {
-		dev_err(&pdev->dev, "can't register reboot mode\n");
-		return error;
+	reason_shift = (long)of_device_get_match_data(&pdev->dev);
+
+	if (reason_shift != NO_REASON_SHIFT) {
+		pon->reboot_mode.dev = &pdev->dev;
+		pon->reason_shift = reason_shift;
+		pon->reboot_mode.write = pm8916_reboot_mode_write;
+		error = devm_reboot_mode_register(&pdev->dev, &pon->reboot_mode);
+		if (error) {
+			dev_err(&pdev->dev, "can't register reboot mode\n");
+			return error;
+		}
 	}
 
 	platform_set_drvdata(pdev, pon);
@@ -80,6 +87,7 @@ static int pm8916_pon_probe(struct platform_device *pdev)
 
 static const struct of_device_id pm8916_pon_id_table[] = {
 	{ .compatible = "qcom,pm8916-pon", .data = (void *)GEN1_REASON_SHIFT },
+	{ .compatible = "qcom,pm8941-pon", .data = (void *)NO_REASON_SHIFT },
 	{ .compatible = "qcom,pms405-pon", .data = (void *)GEN1_REASON_SHIFT },
 	{ .compatible = "qcom,pm8998-pon", .data = (void *)GEN2_REASON_SHIFT },
 	{ .compatible = "qcom,pmk8350-pon", .data = (void *)GEN2_REASON_SHIFT },