pinctrl: mcp23s08: Add optional reset GPIO

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>
Link: https://lore.kernel.org/r/20210610132438.3085841-1-akaessens@gmail.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

diff --git a/drivers/pinctrl/pinctrl-mcp23s08.c b/drivers/pinctrl/pinctrl-mcp23s08.c
index d025957..bccebe4 100644 (file)
--- 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 90dc270..b8d1593 100644 (file)
--- 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;