[PATCH][RFC][resend after bogus] gpio-syscon: do not report bogus error

[PATCH][RFC][resend after bogus] gpio-syscon: do not report bogus error

[Etienne Buira]

Do not call dev_err 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 look like to require gpio,syscon-dev setting.

Signed-off-by: Etienne Buira <etienne.buira@free.fr>
X-Prefers: kind explanations over rotten tomatoes
---
 drivers/gpio/gpio-syscon.c | 28 ++++++++++++++++------------
 1 file changed, 16 insertions(+), 12 deletions(-)

diff --git a/drivers/gpio/gpio-syscon.c b/drivers/gpio/gpio-syscon.c
index 6e1a2581e6ae..14c4f224eb07 100644
--- a/drivers/gpio/gpio-syscon.c
+++ b/drivers/gpio/gpio-syscon.c
@@ -16,6 +16,7 @@
 #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_NODEV	BIT(3)
 
 /* SYSCON driver is designed to use 32-bit wide registers */
 #define SYSCON_REG_SIZE		(4)
@@ -27,7 +28,8 @@
  * @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_NODEV:	gpio,syscon-dev do not have to be set.
  * @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 +151,7 @@ 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_NODEV,
 	.bit_count	= 1,
 	.dat_bit_offset = 0x0428 * 8 + 1,
 	.set		= rockchip_gpio_set,
@@ -221,19 +223,21 @@ 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_NODEV)) {
+		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

Re: [PATCH][RFC][resend after bogus] gpio-syscon: do not report bogus error

[Linus Walleij]

Hi Etienne,

thanks for your patch!

On Thu, Apr 11, 2024 at 5:35 PM Etienne Buira <etienne.buira@free.fr> wrote:

> Do not call dev_err 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 look like to require gpio,syscon-dev setting.
>
> Signed-off-by: Etienne Buira <etienne.buira@free.fr>
> X-Prefers: kind explanations over rotten tomatoes

If you look in drivers/gpio/gpio-syscon.c you see this:

        priv->syscon = syscon_regmap_lookup_by_phandle(np, "gpio,syscon-dev");
        if (IS_ERR(priv->syscon) && np->parent)
                priv->syscon = syscon_node_to_regmap(np->parent);

So the driver will attempt to grab the syscon from the parent if
it can't be located from a gpio,syscon-dev node.

But it's not optional, look in arch/arm64/boot/dts/rockchip/rk3328.dtsi:

        grf: syscon@ff100000 {
                compatible = "rockchip,rk3328-grf", "syscon", "simple-mfd";
                reg = <0x0 0xff100000 0x0 0x1000>;
(...)
                grf_gpio: gpio {
                        compatible = "rockchip,rk3328-grf-gpio";
                        gpio-controller;
                        #gpio-cells = <2>;
                };

So indeed the parent is a sycon, and syscon_node_to_regmap(np->parent) will
be used to populate priv->syscon on RK3328.

So what you could do insteaf of the kludge is something like:

bool has_parent_syscon = false;

priv->syscon = syscon_regmap_lookup_by_phandle(np, "gpio,syscon-dev");
if (IS_ERR(priv->syscon) && np->parent) {
        priv->syscon = syscon_regmap_lookup_by_phandle(np, "gpio,syscon-dev");
        has_parent_syscon = true;
}
if (IS_ERR(priv->syscon))
        return PTR_ERR(priv->syscon);

Then when you get to the code you disable for the flag instead of:

if (!(priv->data->flags & GPIO_SYSCON_FEAT_NODEV)) {
(...)

instead do:

if (!has_parent_syscon) {
(...)

What do you think about this?

Yours,
Linus Walleij

Re: [PATCH][RFC][resend after bogus] gpio-syscon: do not report bogus error

[Etienne Buira]

On Fri, Apr 12, 2024 at 12:44:34PM +0200, Linus Walleij wrote:
> Hi Etienne,
> 
> thanks for your patch!
> 
> On Thu, Apr 11, 2024 at 5:35 PM Etienne Buira <etienne.buira@free.fr> wrote:
> 
> > Do not call dev_err 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 look like to require gpio,syscon-dev setting.
> >
> > Signed-off-by: Etienne Buira <etienne.buira@free.fr>
> > X-Prefers: kind explanations over rotten tomatoes
../..
> So indeed the parent is a sycon, and syscon_node_to_regmap(np->parent) will
> be used to populate priv->syscon on RK3328.
../..
> if (!has_parent_syscon) {
> (...)
> 
> What do you think about this?
../..

Hi Linus,

Thanks for your review.

IIUC, that would prevent calling dev_err() if, for example,
gpio,syscon-dev were forgotten from
arch/arm/boot/dts/ti/keystone/keystone-k2g.dtsi, dspgpio0 node although
it is needed and would result in funny things without notice.

Thinking twice about it, a cleaner way looks to add gpio,syscon-dev node
to rk3328.dtsi. I'll send the one-liner to relevant people (that would
be really easier if there were only one repo, with different
branches...).

Do you agree?

Regards.

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