[PATCH 0/2] mcp23s08: add get_direction and PIN_CONFIG_OUTPUT support.

[PATCH 0/2] mcp23s08: add get_direction and PIN_CONFIG_OUTPUT support.

[Tomaz Solc]

Motivation for these two patches is setting mcp23s08 outputs on boot from the
device tree.

gpio-hog was already functional with mcp23s08, however libgpio incorrectly
showed pins with output-high or output-low hogs as inputs since the driver did
not implement gpio_chip->get_direction().

Many other drivers also support setting pins to output-high or output-low via
pinmux. In contrast to gpio-hog, using pinmux to set the pin state on boot
allows the state to be changed later from user space. mcp23s08 did not support
this since PIN_CONFIG_OUTPUT was not implemented in
pinconf_ops->pin_config_set().

One issue with the second patch is that pins set to output-high or output-low
via pinmux still show up as inputs in libgpio after boot. This is because the
pin direction gets cached in gpio_desc.flags in devm_gpiochip_add_data().
However output-high/-low in pimux only gets applied after that. I am not sure
what would be the best approach to fix this.

Tomaz Solc (2):
  pinctrl: mcp23s08: implement get_direction()
  pinctrl: mcp23s08: support for PIN_CONFIG_OUTPUT.

 .../bindings/pinctrl/pinctrl-mcp23s08.txt     | 12 ++--
 drivers/pinctrl/pinctrl-mcp23s08.c            | 72 ++++++++++++++++---
 2 files changed, 68 insertions(+), 16 deletions(-)

-- 
2.20.1

[PATCH 1/2] pinctrl: mcp23s08: implement get_direction()

[Tomaz Solc]

Signed-off-by: Tomaz Solc <tomaz.solc@tablix.org>
---
 drivers/pinctrl/pinctrl-mcp23s08.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/drivers/pinctrl/pinctrl-mcp23s08.c b/drivers/pinctrl/pinctrl-mcp23s08.c
index bccebe43dd6a..764c93dfd277 100644
--- a/drivers/pinctrl/pinctrl-mcp23s08.c
+++ b/drivers/pinctrl/pinctrl-mcp23s08.c
@@ -339,6 +339,29 @@ mcp23s08_direction_output(struct gpio_chip *chip, unsigned offset, int value)
 	return status;
 }
 
+static int
+mcp23s08_get_direction(struct gpio_chip *chip, unsigned offset)
+{
+	struct mcp23s08	*mcp = gpiochip_get_data(chip);
+	unsigned mask = BIT(offset);
+	int status, ret;
+
+	mutex_lock(&mcp->lock);
+
+	ret = mcp_read(mcp, MCP_IODIR, &status);
+	if (ret == 0) {
+		if(status & mask) {
+			ret = GPIO_LINE_DIRECTION_IN;
+		} else {
+			ret = GPIO_LINE_DIRECTION_OUT;
+		}
+	}
+
+	mutex_unlock(&mcp->lock);
+
+	return ret;
+}
+
 /*----------------------------------------------------------------------*/
 static irqreturn_t mcp23s08_irq(int irq, void *data)
 {
@@ -545,6 +568,7 @@ int mcp23s08_probe_one(struct mcp23s08 *mcp, struct device *dev,
 	mcp->irq_chip.irq_bus_lock = mcp23s08_irq_bus_lock;
 	mcp->irq_chip.irq_bus_sync_unlock = mcp23s08_irq_bus_unlock;
 
+	mcp->chip.get_direction = mcp23s08_get_direction;
 	mcp->chip.direction_input = mcp23s08_direction_input;
 	mcp->chip.get = mcp23s08_get;
 	mcp->chip.direction_output = mcp23s08_direction_output;
-- 
2.20.1

[PATCH 2/2] pinctrl: mcp23s08: support for PIN_CONFIG_OUTPUT.

[Tomaz Solc]

Adds support for setting mcp23s08 pins to output-high or output-low via pinmux
in the device tree.

Signed-off-by: Tomaz Solc <tomaz.solc@tablix.org>
---
 .../bindings/pinctrl/pinctrl-mcp23s08.txt     | 12 ++--
 drivers/pinctrl/pinctrl-mcp23s08.c            | 58 ++++++++++++++-----
 2 files changed, 49 insertions(+), 21 deletions(-)

diff --git a/Documentation/devicetree/bindings/pinctrl/pinctrl-mcp23s08.txt b/Documentation/devicetree/bindings/pinctrl/pinctrl-mcp23s08.txt
index 2fa5edac7a35..483ac9f719a1 100644
--- a/Documentation/devicetree/bindings/pinctrl/pinctrl-mcp23s08.txt
+++ b/Documentation/devicetree/bindings/pinctrl/pinctrl-mcp23s08.txt
@@ -88,11 +88,11 @@ gpiom1: gpio@0 {
         spi-max-frequency = <1000000>;
 };
 
-Pull-up configuration
-=====================
+Pin configuration
+=================
 
-If pins are used as output, they can also be configured with pull-ups. This is
-done with pinctrl.
+If pins are used as inputs, they can also be configured with pull-ups. Pins
+used as outputs can have their default states set. This is done with pinctrl.
 
 Please refer file <devicetree/bindings/pinctrl/pinctrl-bindings.txt>
 for details of the common pinctrl bindings used by client devices,
@@ -121,8 +121,10 @@ The following optional property is defined in the pinmux DT binding document
 <pinctrl-bindings.txt>. Absence of this property will leave the configuration
 in its default state.
 	bias-pull-up
+	output-high
+	output-low
 
-Example with pinctrl to pull-up output pins:
+Example with pinctrl to pull-up input pins:
 gpio21: gpio@21 {
 	compatible = "microchip,mcp23017";
 	gpio-controller;
diff --git a/drivers/pinctrl/pinctrl-mcp23s08.c b/drivers/pinctrl/pinctrl-mcp23s08.c
index 764c93dfd277..81fc7fcef8ec 100644
--- a/drivers/pinctrl/pinctrl-mcp23s08.c
+++ b/drivers/pinctrl/pinctrl-mcp23s08.c
@@ -159,6 +159,26 @@ static int mcp_set_bit(struct mcp23s08 *mcp, unsigned int reg,
 	return mcp_set_mask(mcp, reg, mask, enabled);
 }
 
+static int __mcp23s08_set(struct mcp23s08 *mcp, unsigned mask, bool value)
+{
+	return mcp_set_mask(mcp, MCP_OLAT, mask, value);
+}
+
+static int mcp_direction_output(struct mcp23s08 *mcp, unsigned offset,
+		int value)
+{
+	unsigned mask = BIT(offset);
+	int status;
+
+	mutex_lock(&mcp->lock);
+	status = __mcp23s08_set(mcp, mask, value);
+	if (status == 0) {
+		status = mcp_set_mask(mcp, MCP_IODIR, mask, false);
+	}
+	mutex_unlock(&mcp->lock);
+	return status;
+}
+
 static const struct pinctrl_pin_desc mcp23x08_pins[] = {
 	PINCTRL_PIN(0, "gpio0"),
 	PINCTRL_PIN(1, "gpio1"),
@@ -225,6 +245,7 @@ static int mcp_pinconf_get(struct pinctrl_dev *pctldev, unsigned int pin,
 	enum pin_config_param param = pinconf_to_config_param(*config);
 	unsigned int data, status;
 	int ret;
+	u16 arg;
 
 	switch (param) {
 	case PIN_CONFIG_BIAS_PULL_UP:
@@ -232,12 +253,28 @@ static int mcp_pinconf_get(struct pinctrl_dev *pctldev, unsigned int pin,
 		if (ret < 0)
 			return ret;
 		status = (data & BIT(pin)) ? 1 : 0;
+		arg = 1;
+		break;
+	case PIN_CONFIG_OUTPUT:
+		ret = mcp_read(mcp, MCP_IODIR, &data);
+		if (ret < 0) {
+			return ret;
+		}
+
+		status = (data & BIT(pin)) ? 0 : 1;
+
+		ret = mcp_read(mcp, MCP_OLAT, &data);
+		if (ret < 0) {
+			return ret;
+		}
+
+		arg = (data & BIT(pin)) ? 1 : 0;
 		break;
 	default:
 		return -ENOTSUPP;
 	}
 
-	*config = 0;
+	*config = pinconf_to_config_packed(param, arg);
 
 	return status ? 0 : -EINVAL;
 }
@@ -259,6 +296,9 @@ static int mcp_pinconf_set(struct pinctrl_dev *pctldev, unsigned int pin,
 		case PIN_CONFIG_BIAS_PULL_UP:
 			ret = mcp_set_bit(mcp, MCP_GPPU, pin, arg);
 			break;
+		case PIN_CONFIG_OUTPUT:
+			ret = mcp_direction_output(mcp, pin, arg);
+			break;
 		default:
 			dev_dbg(mcp->dev, "Invalid config param %04x\n", param);
 			return -ENOTSUPP;
@@ -308,11 +348,6 @@ static int mcp23s08_get(struct gpio_chip *chip, unsigned offset)
 	return status;
 }
 
-static int __mcp23s08_set(struct mcp23s08 *mcp, unsigned mask, bool value)
-{
-	return mcp_set_mask(mcp, MCP_OLAT, mask, value);
-}
-
 static void mcp23s08_set(struct gpio_chip *chip, unsigned offset, int value)
 {
 	struct mcp23s08	*mcp = gpiochip_get_data(chip);
@@ -327,16 +362,7 @@ static int
 mcp23s08_direction_output(struct gpio_chip *chip, unsigned offset, int value)
 {
 	struct mcp23s08	*mcp = gpiochip_get_data(chip);
-	unsigned mask = BIT(offset);
-	int status;
-
-	mutex_lock(&mcp->lock);
-	status = __mcp23s08_set(mcp, mask, value);
-	if (status == 0) {
-		status = mcp_set_mask(mcp, MCP_IODIR, mask, false);
-	}
-	mutex_unlock(&mcp->lock);
-	return status;
+	return mcp_direction_output(mcp, offset, value);
 }
 
 static int
-- 
2.20.1