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pinctrl: mcp23s08: Add optional reset GPIO

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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>
This commit is contained in:
Andreas Kaessens 2021-06-10 15:24:37 +02:00 committed by Linus Walleij
parent ca199e1952
commit 4e73bfa3ee
2 changed files with 4 additions and 0 deletions
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3
drivers/pinctrl/pinctrl-mcp23s08.c
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@ -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.
*/

1
drivers/pinctrl/pinctrl-mcp23s08.h
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@ -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;