linux-kernel - [PATCH v2] gpio-syscon: do not report bogus error

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Message-ID: <ZiJkxBU3bYNWOdbK@Z926fQmE5jqhFMgp6>
Date: Fri, 19 Apr 2024 14:34:12 +0200
From: Etienne Buira <etienne.buira@...e.fr>
To: Linus Walleij <linus.walleij@...aro.org>,
	Bartosz Golaszewski <brgl@...ev.pl>, linux-gpio@...r.kernel.org,
	linux-kernel@...r.kernel.org, etienne.buira@...e.fr
Subject: [PATCH v2] gpio-syscon: do not report bogus error

Do not issue "can't read the data register offset!" when gpio,syscon-dev
is not set albeit unneeded.  gpio-syscon is used with rk3328 chip, but
this iomem region is documented in
Documentation/devicetree/bindings/gpio/rockchip,rk3328-grf-gpio.yaml and
does not require gpio,syscon-dev setting.

It has been suggested to automatically detect if node has a valid
parent, but that would defeat the purpose of error message, for example
arch/arm/boot/dts/ti/keystone/keystone-k2g.dtsi could then be used
without gpio,syscon-dev, and lead to funny results without error
message.

It has been tried to mandate use of gpio,syscon-dev, but that raised
objection.

So while this patch may be kludgy, it looks the less bad to address
the spurious dev_err call.

v2:
  - changed flag name

Signed-off-by: Etienne Buira <etienne.buira@...e.fr>
---
 drivers/gpio/gpio-syscon.c | 35 ++++++++++++++++++++---------------
 1 file changed, 20 insertions(+), 15 deletions(-)

diff --git a/drivers/gpio/gpio-syscon.c b/drivers/gpio/gpio-syscon.c
index 6e1a2581e6ae..4f103ce26019 100644
--- a/drivers/gpio/gpio-syscon.c
+++ b/drivers/gpio/gpio-syscon.c
@@ -13,9 +13,10 @@
 #include <linux/regmap.h>
 #include <linux/mfd/syscon.h>
 
-#define GPIO_SYSCON_FEAT_IN	BIT(0)
-#define GPIO_SYSCON_FEAT_OUT	BIT(1)
-#define GPIO_SYSCON_FEAT_DIR	BIT(2)
+#define GPIO_SYSCON_FEAT_IN		BIT(0)
+#define GPIO_SYSCON_FEAT_OUT		BIT(1)
+#define GPIO_SYSCON_FEAT_DIR		BIT(2)
+#define GPIO_SYSCON_FEAT_USE_PARENT	BIT(3)
 
 /* SYSCON driver is designed to use 32-bit wide registers */
 #define SYSCON_REG_SIZE		(4)
@@ -27,7 +28,9 @@
  * @flags:		Set of GPIO_SYSCON_FEAT_ flags:
  *			GPIO_SYSCON_FEAT_IN:	GPIOs supports input,
  *			GPIO_SYSCON_FEAT_OUT:	GPIOs supports output,
- *			GPIO_SYSCON_FEAT_DIR:	GPIOs supports switch direction.
+ *			GPIO_SYSCON_FEAT_DIR:	GPIOs supports switch direction,
+ *			GPIO_SYSCON_FEAT_USE_PARENT:	gpio,syscon-dev do not
+ *				have to be set, parent regspace will be used.
  * @bit_count:		Number of bits used as GPIOs.
  * @dat_bit_offset:	Offset (in bits) to the first GPIO bit.
  * @dir_bit_offset:	Optional offset (in bits) to the first bit to switch
@@ -149,7 +152,7 @@ static void rockchip_gpio_set(struct gpio_chip *chip, unsigned int offset,
 
 static const struct syscon_gpio_data rockchip_rk3328_gpio_mute = {
 	/* RK3328 GPIO_MUTE is an output only pin at GRF_SOC_CON10[1] */
-	.flags		= GPIO_SYSCON_FEAT_OUT,
+	.flags		= GPIO_SYSCON_FEAT_OUT | GPIO_SYSCON_FEAT_USE_PARENT,
 	.bit_count	= 1,
 	.dat_bit_offset = 0x0428 * 8 + 1,
 	.set		= rockchip_gpio_set,
@@ -221,19 +224,21 @@ static int syscon_gpio_probe(struct platform_device *pdev)
 	if (IS_ERR(priv->syscon))
 		return PTR_ERR(priv->syscon);
 
-	ret = of_property_read_u32_index(np, "gpio,syscon-dev", 1,
-					 &priv->dreg_offset);
-	if (ret)
-		dev_err(dev, "can't read the data register offset!\n");
+	if (!(priv->data->flags & GPIO_SYSCON_FEAT_USE_PARENT)) {
+		ret = of_property_read_u32_index(np, "gpio,syscon-dev", 1,
+						 &priv->dreg_offset);
+		if (ret)
+			dev_err(dev, "can't read the data register offset!\n");
 
-	priv->dreg_offset <<= 3;
+		priv->dreg_offset <<= 3;
 
-	ret = of_property_read_u32_index(np, "gpio,syscon-dev", 2,
-					 &priv->dir_reg_offset);
-	if (ret)
-		dev_dbg(dev, "can't read the dir register offset!\n");
+		ret = of_property_read_u32_index(np, "gpio,syscon-dev", 2,
+						 &priv->dir_reg_offset);
+		if (ret)
+			dev_dbg(dev, "can't read the dir register offset!\n");
 
-	priv->dir_reg_offset <<= 3;
+		priv->dir_reg_offset <<= 3;
+	}
 
 	priv->chip.parent = dev;
 	priv->chip.owner = THIS_MODULE;

base-commit: 4cece764965020c22cff7665b18a012006359095
-- 
2.43.0