From: Andreas Kaessens <akaessens@gmail.com>
To: linus.walleij@linaro.org, robh+dt@kernel.org,
linux-gpio@vger.kernel.org, devicetree@vger.kernel.org,
linux-kernel@vger.kernel.org
Cc: linux-kernel@i4.cs.fau.de, Andreas Kaessens <akaessens@gmail.com>,
Darian Biastoch <d.biastoch@gmail.com>
Subject: [PATCH 1/2] pinctrl: mcp23s08: Add optional reset GPIO
Date: Thu, 10 Jun 2021 15:24:37 +0200 [thread overview]
Message-ID: <20210610132438.3085841-1-akaessens@gmail.com> (raw)
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
next reply other threads:[~2021-06-10 13:25 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-10 13:24 Andreas Kaessens [this message]
2021-06-10 13:24 ` [PATCH 2/2] dt-bindings: pinctrl: mcp23s08: add documentation for reset-gpios Andreas Kaessens
2021-06-11 23:59 ` [PATCH 1/2] pinctrl: mcp23s08: Add optional reset GPIO Linus Walleij
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