linux-kernel - [PATCH] gpio: gpio-pca953x: do not enable regmap cache when there is no regulator

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Message-Id: <20241127071450.3082761-1-haibo.chen@nxp.com>
Date: Wed, 27 Nov 2024 15:14:50 +0800
From: haibo.chen@....com
To: linus.walleij@...aro.org,
	brgl@...ev.pl
Cc: lgirdwood@...il.com,
	broonie@...nel.org,
	linux-gpio@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	imx@...ts.linux.dev,
	marek.vasut@...il.com,
	haibo.chen@....com
Subject: [PATCH] gpio: gpio-pca953x: do not enable regmap cache when there is no regulator

From: Haibo Chen <haibo.chen@....com>

Regmap cache mechanism is enabled in default. Thus, IO expander wouldn't
handle GPIO set really before resuming back.

But there are cases need to toggle gpio in NO_IRQ stage.
e.g. To align with PCIe specification, PERST# signal connected on the IO
expander must be toggled during PCIe RC's NO_IRQ_RESUME.

Do not enable the regmap cache when IO expander doesn't have the regulator
during system PM. That means the power of IO expander would be kept on,
and the GPIOs of the IO expander can be toggled really during system PM.

Signed-off-by: Haibo Chen <haibo.chen@....com>
---
 drivers/gpio/gpio-pca953x.c | 35 ++++++++++++++++++++++++++---------
 1 file changed, 26 insertions(+), 9 deletions(-)

diff --git a/drivers/gpio/gpio-pca953x.c b/drivers/gpio/gpio-pca953x.c
index 272febc3230e..6503ef0d7562 100644
--- a/drivers/gpio/gpio-pca953x.c
+++ b/drivers/gpio/gpio-pca953x.c
@@ -1040,9 +1040,15 @@ static int pca953x_get_and_enable_regulator(struct pca953x_chip *chip)
 	struct regulator *reg = chip->regulator;
 	int ret;
 
-	reg = devm_regulator_get(dev, "vcc");
-	if (IS_ERR(reg))
-		return dev_err_probe(dev, PTR_ERR(reg), "reg get err\n");
+	reg = devm_regulator_get_optional(dev, "vcc");
+	if (IS_ERR(reg)) {
+		if (PTR_ERR(reg) == -ENODEV) {
+			chip->regulator = NULL;
+			return 0;
+		} else {
+			return dev_err_probe(dev, PTR_ERR(reg), "reg get err\n");
+		}
+	}
 
 	ret = regulator_enable(reg);
 	if (ret)
@@ -1240,11 +1246,20 @@ static int pca953x_suspend(struct device *dev)
 {
 	struct pca953x_chip *chip = dev_get_drvdata(dev);
 
-	pca953x_save_context(chip);
+	/*
+	 * Only save context when has regulator, if no
+	 * regulator, power keeps on, can also handle
+	 * gpio related operation.
+	 * e.g. PCIe RC need to toggle the RST pin in
+	 * NOIRQ resume stage, so can't open regmap
+	 * cache if there is no regulator.
+	 */
+	if (chip->regulator)
+		pca953x_save_context(chip);
 
 	if (atomic_read(&chip->wakeup_path))
 		device_set_wakeup_path(dev);
-	else
+	else if (chip->regulator)
 		regulator_disable(chip->regulator);
 
 	return 0;
@@ -1255,7 +1270,7 @@ static int pca953x_resume(struct device *dev)
 	struct pca953x_chip *chip = dev_get_drvdata(dev);
 	int ret;
 
-	if (!atomic_read(&chip->wakeup_path)) {
+	if (!atomic_read(&chip->wakeup_path) && chip->regulator) {
 		ret = regulator_enable(chip->regulator);
 		if (ret) {
 			dev_err(dev, "Failed to enable regulator: %d\n", ret);
@@ -1263,9 +1278,11 @@ static int pca953x_resume(struct device *dev)
 		}
 	}
 
-	ret = pca953x_restore_context(chip);
-	if (ret)
-		dev_err(dev, "Failed to restore register map: %d\n", ret);
+	if (chip->regulator) {
+		ret = pca953x_restore_context(chip);
+		if (ret)
+			dev_err(dev, "Failed to restore register map: %d\n", ret);
+	}
 
 	return ret;
 }
-- 
2.34.1