[PATCH 1/2] pinctrl: mcp23s08: Add optional reset GPIO

[PATCH 1/2] pinctrl: mcp23s08: Add optional reset GPIO

[Andreas Kaessens]

The MCP23x port expander RESET# line can be connected to a host GPIO.
The optional reset-gpio must be set to LOW if the reset is asserted
at probing time.

On page 5 in the datasheet [0] the "Device Active After Reset high"
time is specified at 0 µs. Therefore no waiting is needed after the
reset transition.

[0] https://ww1.microchip.com/downloads/en/DeviceDoc/20001952C.pdf

Signed-off-by: Andreas Kaessens <akaessens@gmail.com>
Signed-off-by: Darian Biastoch <d.biastoch@gmail.com>
---
 drivers/pinctrl/pinctrl-mcp23s08.c | 3 +++
 drivers/pinctrl/pinctrl-mcp23s08.h | 1 +
 2 files changed, 4 insertions(+)

diff --git a/drivers/pinctrl/pinctrl-mcp23s08.c b/drivers/pinctrl/pinctrl-mcp23s08.c
index 799d596a1a4b..8ab254170d99 100644
--- a/drivers/pinctrl/pinctrl-mcp23s08.c
+++ b/drivers/pinctrl/pinctrl-mcp23s08.c
@@ -9,6 +9,7 @@
 #include <linux/module.h>
 #include <linux/export.h>
 #include <linux/gpio/driver.h>
+#include <linux/gpio/consumer.h>
 #include <linux/slab.h>
 #include <asm/byteorder.h>
 #include <linux/interrupt.h>
@@ -558,6 +559,8 @@ int mcp23s08_probe_one(struct mcp23s08 *mcp, struct device *dev,
 	mcp->chip.parent = dev;
 	mcp->chip.owner = THIS_MODULE;
 
+	mcp->reset_gpio = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_LOW);
+
 	/* verify MCP_IOCON.SEQOP = 0, so sequential reads work,
 	 * and MCP_IOCON.HAEN = 1, so we work with all chips.
 	 */
diff --git a/drivers/pinctrl/pinctrl-mcp23s08.h b/drivers/pinctrl/pinctrl-mcp23s08.h
index 90dc27081a3c..b8d15939e0c2 100644
--- a/drivers/pinctrl/pinctrl-mcp23s08.h
+++ b/drivers/pinctrl/pinctrl-mcp23s08.h
@@ -43,6 +43,7 @@ struct mcp23s08 {
 
 	struct pinctrl_dev	*pctldev;
 	struct pinctrl_desc	pinctrl_desc;
+	struct gpio_desc        *reset_gpio;
 };
 
 extern const struct regmap_config mcp23x08_regmap;
-- 
2.25.1

[PATCH 2/2] dt-bindings: pinctrl: mcp23s08: add documentation for reset-gpios

[Andreas Kaessens]

The reset-gpios property is added to the optional dt-bindings and
also an example for it's usage.

Signed-off-by: Andreas Kaessens <akaessens@gmail.com>
Signed-off-by: Darian Biastoch <d.biastoch@gmail.com>
---
 Documentation/devicetree/bindings/pinctrl/pinctrl-mcp23s08.txt | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/Documentation/devicetree/bindings/pinctrl/pinctrl-mcp23s08.txt b/Documentation/devicetree/bindings/pinctrl/pinctrl-mcp23s08.txt
index 6ec3c8d79f49..2fa5edac7a35 100644
--- a/Documentation/devicetree/bindings/pinctrl/pinctrl-mcp23s08.txt
+++ b/Documentation/devicetree/bindings/pinctrl/pinctrl-mcp23s08.txt
@@ -49,6 +49,7 @@ Optional properties:
 - interrupt-controller: Marks the device node as a interrupt controller.
 - drive-open-drain: Sets the ODR flag in the IOCON register. This configures
         the IRQ output as open drain active low.
+- reset-gpios: Corresponds to the active-low RESET# pin for the chip
 
 Optional device specific properties:
 - microchip,irq-mirror: Sets the mirror flag in the IOCON register. Devices
@@ -135,6 +136,7 @@ gpio21: gpio@21 {
 	microchip,irq-mirror;
 	pinctrl-names = "default";
 	pinctrl-0 = <&i2cgpio0irq>, <&gpio21pullups>;
+	reset-gpios = <&gpio6 15 GPIO_ACTIVE_LOW>;
 
 	gpio21pullups: pinmux {
 		pins =	"gpio0", "gpio1", "gpio2", "gpio3",
-- 
2.25.1

Re: [PATCH 1/2] pinctrl: mcp23s08: Add optional reset GPIO

[Linus Walleij]

On Thu, Jun 10, 2021 at 3:24 PM Andreas Kaessens <akaessens@gmail.com> wrote:

> The MCP23x port expander RESET# line can be connected to a host GPIO.
> The optional reset-gpio must be set to LOW if the reset is asserted
> at probing time.
>
> On page 5 in the datasheet [0] the "Device Active After Reset high"
> time is specified at 0 µs. Therefore no waiting is needed after the
> reset transition.
>
> [0] https://ww1.microchip.com/downloads/en/DeviceDoc/20001952C.pdf
>
> Signed-off-by: Andreas Kaessens <akaessens@gmail.com>
> Signed-off-by: Darian Biastoch <d.biastoch@gmail.com>

Both patches applied, thanks!

Yours,
Linus Walleij