[PATCH v2 0/5] GPIO driver for Maxim MAX3191x

[PATCH v2 0/5] GPIO driver for Maxim MAX3191x

[Lukas Wunner]

GPIO driver for Maxim MAX31910, MAX31911, MAX31912, MAX31913,
MAX31953 and MAX31963 industrial serializer, a daisy-chainable
chip to make 8 digital 24V inputs available via SPI.  Supports
CRC checksums to guard against electromagnetic interference,
as well as undervoltage and overtemperature detection.

The chip is used by the "Revolution Pi" family of open source PLCs
based on the Raspberry Pi (https://revolution.kunbus.com/).

In a typical SCADA system, all input signals are read periodically,
say, every 5 or 10 ms, and stored in a so-called "process image".
To make this perform well with serializers, add a ->get_multiple
callback to struct gpio_chip, add corresponding consumer functions
and wire it up with linehandle_ioctl().

Changes v1 -> v2:

- Patch [1/5]: Change the argument order of assign_bit() to reflect
  traditional "dst = src" in C. (Peter Zijlstra)

- Patch [2/5]: Update documentation. (Linus Walleij)
  Drop const qualifier from struct gpio_desc ** in all function
  signatures to avoid a cast when passing a non-const array created
  with gpiod_get_array(), which is likely the most common use case.

- Patch [3/5]: Newly inserted patch to introduce common property for
  number of daisy-chained devices.

- Patch [4/5]: Add vendor prefix to GPIO identifiers, use boolean
  instead of integer to select mode, rename boolean to ignore
  undervoltage alarms, separate compatible strings with newlines.
  (Rob Herring)

- Patch [5/5]: Optimize algorithm in max3191x_get_multiple() to
  iterate over the bits in the mask, instead of iterating over every
  chip, thus implicitly skipping chips which are not selected at all
  by the mask.
  Support configurations where all chips in a daisy-chain share the
  same modesel, fault or debounce pin.
  Verify that the number of db0 and db1 GPIOs specified in the DT is
  identical.

Link to v1:

https://www.spinics.net/lists/linux-gpio/msg25067.html

Thanks,

Lukas


Lukas Wunner (5):
  bitops: Introduce assign_bit()
  gpio: Introduce ->get_multiple callback
  dt-bindings: Document common property for daisy-chained devices
  dt-bindings: gpio: max3191x: Document new driver
  gpio: Add driver for Maxim MAX3191x industrial serializer

 .../devicetree/bindings/common-properties.txt      |  26 ++
 .../devicetree/bindings/gpio/gpio-max3191x.txt     |  59 +++
 Documentation/gpio/consumer.txt                    |  41 +-
 drivers/gpio/Kconfig                               |  10 +
 drivers/gpio/Makefile                              |   1 +
 drivers/gpio/gpio-max3191x.c                       | 492 +++++++++++++++++++++
 drivers/gpio/gpiolib.c                             | 179 +++++++-
 drivers/gpio/gpiolib.h                             |   4 +
 drivers/md/dm-mpath.c                              |  22 +-
 include/linux/bitops.h                             |  24 +
 include/linux/gpio/consumer.h                      |  43 ++
 include/linux/gpio/driver.h                        |   5 +
 12 files changed, 869 insertions(+), 37 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/gpio/gpio-max3191x.txt
 create mode 100644 drivers/gpio/gpio-max3191x.c

-- 
2.11.0

[PATCH v2 3/5] dt-bindings: Document common property for daisy-chained devices

[Lukas Wunner]

Many serially-attached GPIO and IIO devices are daisy-chainable.

    Examples for GPIO devices are Maxim MAX3191x and TI SN65HVS88x:
    https://datasheets.maximintegrated.com/en/ds/MAX31913.pdf
    http://www.ti.com/lit/ds/symlink/sn65hvs880.pdf

    Examples for IIO devices are TI DAC128S085 and TI DAC161S055:
    http://www.ti.com/lit/ds/symlink/dac128s085.pdf
    http://www.ti.com/lit/ds/symlink/dac161s055.pdf

We already have drivers for daisy-chainable devices in the tree but
their devicetree bindings are somewhat inconsistent and ill-named:

    The gpio-74x164.c driver uses "registers-number" to convey the
    number of devices in the daisy-chain.  (Sans vendor prefix,
    multiple vendors sell compatible versions of this chip.)

    The gpio-pisosr.c driver takes a different approach and calculates
    the number of devices in the daisy-chain by dividing the common
    "ngpios" property (Documentation/devicetree/bindings/gpio/gpio.txt)
    by 8 (which assumes that each chip has 8 inputs).

Let's standardize on a common "#daisy-chained-devices" property.
That name was chosen because it's the term most frequently used in
datasheets.  (A less frequently used synonym is "cascaded devices".)

Signed-off-by: Lukas Wunner <lukas@wunner.de>
---
Changes v1 -> v2:

- Newly inserted patch.

 .../devicetree/bindings/common-properties.txt      | 26 ++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/Documentation/devicetree/bindings/common-properties.txt b/Documentation/devicetree/bindings/common-properties.txt
index 697714f8d75c..a3448bfa1c82 100644
--- a/Documentation/devicetree/bindings/common-properties.txt
+++ b/Documentation/devicetree/bindings/common-properties.txt
@@ -1,4 +1,8 @@
 Common properties
+=================
+
+Endianness
+----------
 
 The Devicetree Specification does not define any properties related to hardware
 byteswapping, but endianness issues show up frequently in porting Linux to
@@ -58,3 +62,25 @@ dev: dev@40031000 {
 	      ...
 	      little-endian;
 };
+
+Daisy-chained devices
+---------------------
+
+Many serially-attached GPIO and IIO devices are daisy-chainable.  To the
+host controller, a daisy-chain appears as a single device, but the number
+of inputs and outputs it provides is the sum of inputs and outputs provided
+by all of its devices.  The driver needs to know how many devices the
+daisy-chain comprises to determine the amount of data exchanged, how many
+inputs and outputs to register and so on.
+
+Optional properties:
+ - #daisy-chained-devices: Number of devices in the daisy-chain (default is 1).
+
+Example:
+gpio@0 {
+	      compatible = "name";
+	      reg = <0>;
+	      gpio-controller;
+	      #gpio-cells = <2>;
+	      #daisy-chained-devices = <3>;
+};
-- 
2.11.0

[PATCH v2 4/5] dt-bindings: gpio: max3191x: Document new driver

[Lukas Wunner]

Add device tree bindings for Maxim MAX3191x industrial serializer.

Cc: Mathias Duckeck <m.duckeck-XB/JSsFECOqzQB+pC5nmwQ@public.gmane.org>
Signed-off-by: Lukas Wunner <lukas-JFq808J9C/izQB+pC5nmwQ@public.gmane.org>
---
Changes v1 -> v2:

- Add vendor prefix to GPIO identifiers, use boolean instead of
  integer to select mode, rename boolean to ignore undervoltage
  alarms, separate compatible strings with newlines. (Rob Herring)

 .../devicetree/bindings/gpio/gpio-max3191x.txt     | 59 ++++++++++++++++++++++
 1 file changed, 59 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/gpio/gpio-max3191x.txt

diff --git a/Documentation/devicetree/bindings/gpio/gpio-max3191x.txt b/Documentation/devicetree/bindings/gpio/gpio-max3191x.txt
new file mode 100644
index 000000000000..b3a6444b8f45
--- /dev/null
+++ b/Documentation/devicetree/bindings/gpio/gpio-max3191x.txt
@@ -0,0 +1,59 @@
+GPIO driver for Maxim MAX3191x industrial serializer
+
+Required properties:
+ - compatible:		Must be one of:
+			"maxim,max31910"
+			"maxim,max31911"
+			"maxim,max31912"
+			"maxim,max31913"
+			"maxim,max31953"
+			"maxim,max31963"
+ - reg: 		Chip select number.
+ - gpio-controller:	Marks the device node as a GPIO controller.
+ - #gpio-cells: 	Should be two. For consumer use see gpio.txt.
+
+Optional properties:
+ - #daisy-chained-devices:
+			Number of chips in the daisy-chain (default is 1).
+ - maxim,modesel-gpios: GPIO pins to configure modesel of each chip.
+			The number of GPIOs must equal "#daisy-chained-devices"
+			(if each chip is driven by a separate pin) or 1
+			(if all chips are wired to the same pin).
+ - maxim,fault-gpios: 	GPIO pins to read fault of each chip.
+			The number of GPIOs must equal "#daisy-chained-devices"
+			or 1.
+ - maxim,db0-gpios:	GPIO pins to configure debounce of each chip.
+			The number of GPIOs must equal "#daisy-chained-devices"
+			or 1.
+ - maxim,db1-gpios:	GPIO pins to configure debounce of each chip.
+			The number of GPIOs must equal "maxim,db0-gpios".
+ - maxim,modesel-8bit:	Boolean whether the modesel pin of the chips is
+			pulled high (8-bit mode).  Use this if the modesel pin
+			is hardwired and consequently "maxim,modesel-gpios"
+			cannot be specified.  By default if neither this nor
+			"maxim,modesel-gpios" is given, the driver assumes
+			that modesel is pulled low (16-bit mode).
+ - maxim,ignore-undervoltage:
+			Boolean whether to ignore undervoltage alarms signaled
+			by the "maxim,fault-gpios" or by the status byte
+			(in 16-bit mode).  Use this if the chips are powered
+			through 5VOUT instead of VCC24V, in which case they
+			will constantly signal undervoltage.
+
+For other required and optional properties of SPI slave nodes please refer to
+../spi/spi-bus.txt.
+
+Example:
+	gpio@0 {
+		compatible = "maxim,max31913";
+		reg = <0>;
+		gpio-controller;
+		#gpio-cells = <2>;
+
+		maxim,modesel-gpios = <&gpio2 23>;
+		maxim,fault-gpios   = <&gpio2 24 GPIO_ACTIVE_LOW>;
+		maxim,db0-gpios     = <&gpio2 25>;
+		maxim,db1-gpios     = <&gpio2 26>;
+
+		spi-max-frequency = <25000000>;
+	};
-- 
2.11.0

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[PATCH v2 5/5] gpio: Add driver for Maxim MAX3191x industrial serializer

[Lukas Wunner]

The driver was developed for and tested with the MAX31913 built into
the Revolution Pi by KUNBUS, but should work with all members of the
MAX3191x family:

MAX31910: low power
MAX31911: LED drivers
MAX31912: LED drivers + 2nd voltage monitor + low power
MAX31913: LED drivers + 2nd voltage monitor
MAX31953: LED drivers + 2nd voltage monitor + isolation
MAX31963: LED drivers + 2nd voltage monitor + isolation + buck regulator

Cc: Mathias Duckeck <m.duckeck-XB/JSsFECOqzQB+pC5nmwQ@public.gmane.org>
Signed-off-by: Lukas Wunner <lukas-JFq808J9C/izQB+pC5nmwQ@public.gmane.org>
---
Changes v1 -> v2:

- Optimize algorithm in max3191x_get_multiple() to iterate over the
  bits in the mask, instead of iterating over every chip, thus
  implicitly skipping chips which are not selected at all by the mask.
  Support configurations where all chips in a daisy-chain share the
  same modesel, fault or debounce pin.
  Verify that the number of db0 and db1 GPIOs specified in the DT is
  identical.

 drivers/gpio/Kconfig         |  10 +
 drivers/gpio/Makefile        |   1 +
 drivers/gpio/gpio-max3191x.c | 492 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 503 insertions(+)
 create mode 100644 drivers/gpio/gpio-max3191x.c

diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 3388d54ba114..d5282cac6ea6 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -1255,6 +1255,16 @@ config GPIO_74X164
 	  shift registers. This driver can be used to provide access
 	  to more gpio outputs.
 
+config GPIO_MAX3191X
+	tristate "Maxim MAX3191x industrial serializer"
+	select CRC8
+	help
+	  GPIO driver for Maxim MAX31910, MAX31911, MAX31912, MAX31913,
+	  MAX31953 and MAX31963 industrial serializer, a daisy-chainable
+	  chip to make 8 digital 24V inputs available via SPI.  Supports
+	  CRC checksums to guard against electromagnetic interference,
+	  as well as undervoltage and overtemperature detection.
+
 config GPIO_MAX7301
 	tristate "Maxim MAX7301 GPIO expander"
 	select GPIO_MAX730X
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index aeb70e9de6f2..cf9ecfb24ef4 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -69,6 +69,7 @@ obj-$(CONFIG_ARCH_LPC32XX)	+= gpio-lpc32xx.o
 obj-$(CONFIG_GPIO_LP873X)	+= gpio-lp873x.o
 obj-$(CONFIG_GPIO_LP87565)	+= gpio-lp87565.o
 obj-$(CONFIG_GPIO_LYNXPOINT)	+= gpio-lynxpoint.o
+obj-$(CONFIG_GPIO_MAX3191X)	+= gpio-max3191x.o
 obj-$(CONFIG_GPIO_MAX730X)	+= gpio-max730x.o
 obj-$(CONFIG_GPIO_MAX7300)	+= gpio-max7300.o
 obj-$(CONFIG_GPIO_MAX7301)	+= gpio-max7301.o
diff --git a/drivers/gpio/gpio-max3191x.c b/drivers/gpio/gpio-max3191x.c
new file mode 100644
index 000000000000..f74b1072e84b
--- /dev/null
+++ b/drivers/gpio/gpio-max3191x.c
@@ -0,0 +1,492 @@
+/*
+ * gpio-max3191x.c - GPIO driver for Maxim MAX3191x industrial serializer
+ *
+ * Copyright (C) 2017 KUNBUS GmbH
+ *
+ * The MAX3191x makes 8 digital 24V inputs available via SPI.
+ * Multiple chips can be daisy-chained, the spec does not impose
+ * a limit on the number of chips and neither does this driver.
+ *
+ * Either of two modes is selectable: In 8-bit mode, only the state
+ * of the inputs is clocked out to achieve high readout speeds;
+ * In 16-bit mode, an additional status byte is clocked out with
+ * a CRC and indicator bits for undervoltage and overtemperature.
+ * The driver returns an error instead of potentially bogus data
+ * if any of these fault conditions occur.  However it does allow
+ * readout of non-faulting chips in the same daisy-chain.
+ *
+ * MAX3191x supports four debounce settings and the driver is
+ * capable of configuring these differently for each chip in the
+ * daisy-chain.
+ *
+ * If the chips are hardwired to 8-bit mode ("modesel" pulled high),
+ * gpio-pisosr.c can be used alternatively to this driver.
+ *
+ * https://datasheets.maximintegrated.com/en/ds/MAX31910.pdf
+ * https://datasheets.maximintegrated.com/en/ds/MAX31911.pdf
+ * https://datasheets.maximintegrated.com/en/ds/MAX31912.pdf
+ * https://datasheets.maximintegrated.com/en/ds/MAX31913.pdf
+ * https://datasheets.maximintegrated.com/en/ds/MAX31953-MAX31963.pdf
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License (version 2) as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/bitmap.h>
+#include <linux/crc8.h>
+#include <linux/gpio/consumer.h>
+#include <linux/gpio/driver.h>
+#include <linux/module.h>
+#include <linux/spi/spi.h>
+
+enum max3191x_mode {
+	STATUS_BYTE_ENABLED,
+	STATUS_BYTE_DISABLED,
+};
+
+/**
+ * struct max3191x_chip - max3191x daisy-chain
+ * @gpio: GPIO controller struct
+ * @lock: protects read sequences
+ * @nchips: number of chips in the daisy-chain
+ * @mode: current mode, 0 for 16-bit, 1 for 8-bit;
+ *	for simplicity, all chips in the daisy-chain are assumed
+ *	to use the same mode
+ * @modesel_pins: GPIO pins to configure modesel of each chip
+ * @fault_pins: GPIO pins to detect fault of each chip
+ * @db0_pins: GPIO pins to configure debounce of each chip
+ * @db1_pins: GPIO pins to configure debounce of each chip
+ * @mesg: SPI message to perform a readout
+ * @xfer: SPI transfer used by @mesg
+ * @crc_error: bitmap signaling CRC error for each chip
+ * @overtemp: bitmap signaling overtemperature alarm for each chip
+ * @undervolt1: bitmap signaling undervoltage alarm for each chip
+ * @undervolt2: bitmap signaling undervoltage warning for each chip
+ * @fault: bitmap signaling assertion of @fault_pins for each chip
+ * @ignore_uv: whether to ignore undervoltage alarms;
+ *	set by a device property if the chips are powered through
+ *	5VOUT instead of VCC24V, in which case they will constantly
+ *	signal undervoltage;
+ *	for simplicity, all chips in the daisy-chain are assumed
+ *	to be powered the same way
+ */
+struct max3191x_chip {
+	struct gpio_chip gpio;
+	struct mutex lock;
+	u32 nchips;
+	enum max3191x_mode mode;
+	struct gpio_descs *modesel_pins;
+	struct gpio_descs *fault_pins;
+	struct gpio_descs *db0_pins;
+	struct gpio_descs *db1_pins;
+	struct spi_message mesg;
+	struct spi_transfer xfer;
+	unsigned long *crc_error;
+	unsigned long *overtemp;
+	unsigned long *undervolt1;
+	unsigned long *undervolt2;
+	unsigned long *fault;
+	bool ignore_uv;
+};
+
+#define MAX3191X_NGPIO 8
+#define MAX3191X_CRC8_POLYNOMIAL 0xa8 /* (x^5) + x^4 + x^2 + x^0 */
+
+DECLARE_CRC8_TABLE(max3191x_crc8);
+
+static int max3191x_get_direction(struct gpio_chip *gpio, unsigned int offset)
+{
+	return 1; /* always in */
+}
+
+static int max3191x_direction_input(struct gpio_chip *gpio, unsigned int offset)
+{
+	return 0;
+}
+
+static int max3191x_direction_output(struct gpio_chip *gpio,
+				     unsigned int offset, int value)
+{
+	return -EINVAL;
+}
+
+static void max3191x_set(struct gpio_chip *gpio, unsigned int offset, int value)
+{ }
+
+static void max3191x_set_multiple(struct gpio_chip *gpio, unsigned long *mask,
+				  unsigned long *bits)
+{ }
+
+static unsigned int max3191x_wordlen(struct max3191x_chip *max3191x)
+{
+	return max3191x->mode == STATUS_BYTE_ENABLED ? 2 : 1;
+}
+
+static int max3191x_readout_locked(struct max3191x_chip *max3191x)
+{
+	struct device *dev = max3191x->gpio.parent;
+	struct spi_device *spi = to_spi_device(dev);
+	int val, i, ot = 0, uv1 = 0;
+
+	val = spi_sync(spi, &max3191x->mesg);
+	if (val) {
+		dev_err_ratelimited(dev, "SPI receive error %d\n", val);
+		return val;
+	}
+
+	for (i = 0; i < max3191x->nchips; i++) {
+		if (max3191x->mode == STATUS_BYTE_ENABLED) {
+			u8 in	  = ((u8 *)max3191x->xfer.rx_buf)[i * 2];
+			u8 status = ((u8 *)max3191x->xfer.rx_buf)[i * 2 + 1];
+
+			val = (status & 0xf8) != crc8(max3191x_crc8, &in, 1, 0);
+			__assign_bit(i, max3191x->crc_error, val);
+			if (val)
+				dev_err_ratelimited(dev,
+					"chip %d: CRC error\n", i);
+
+			ot  = (status >> 1) & 1;
+			__assign_bit(i, max3191x->overtemp, ot);
+			if (ot)
+				dev_err_ratelimited(dev,
+					"chip %d: overtemperature\n", i);
+
+			if (!max3191x->ignore_uv) {
+				uv1 = !((status >> 2) & 1);
+				__assign_bit(i, max3191x->undervolt1, uv1);
+				if (uv1)
+					dev_err_ratelimited(dev,
+						"chip %d: undervoltage\n", i);
+
+				val = !(status & 1);
+				__assign_bit(i, max3191x->undervolt2, val);
+				if (val && !uv1)
+					dev_warn_ratelimited(dev,
+						"chip %d: voltage warn\n", i);
+			}
+		}
+
+		if (max3191x->fault_pins && !max3191x->ignore_uv) {
+			/* fault pin shared by all chips or per chip */
+			struct gpio_desc *fault_pin =
+				(max3191x->fault_pins->ndescs == 1)
+					? max3191x->fault_pins->desc[0]
+					: max3191x->fault_pins->desc[i];
+
+			val = gpiod_get_value_cansleep(fault_pin);
+			if (val < 0) {
+				dev_err_ratelimited(dev,
+					"GPIO read error %d\n", val);
+				return val;
+			}
+			__assign_bit(i, max3191x->fault, val);
+			if (val && !uv1 && !ot)
+				dev_err_ratelimited(dev,
+					"chip %d: fault\n", i);
+		}
+	}
+
+	return 0;
+}
+
+static bool max3191x_chip_is_faulting(struct max3191x_chip *max3191x,
+				      unsigned int chipnum)
+{
+	/* without status byte the only diagnostic is the fault pin */
+	if (!max3191x->ignore_uv && test_bit(chipnum, max3191x->fault))
+		return true;
+
+	if (max3191x->mode == STATUS_BYTE_DISABLED)
+		return false;
+
+	return test_bit(chipnum, max3191x->crc_error) ||
+	       test_bit(chipnum, max3191x->overtemp)  ||
+	       (!max3191x->ignore_uv &&
+		test_bit(chipnum, max3191x->undervolt1));
+}
+
+static int max3191x_get(struct gpio_chip *gpio, unsigned int offset)
+{
+	struct max3191x_chip *max3191x = gpiochip_get_data(gpio);
+	int ret, chipnum, wordlen = max3191x_wordlen(max3191x);
+	u8 in;
+
+	mutex_lock(&max3191x->lock);
+	ret = max3191x_readout_locked(max3191x);
+	if (ret)
+		goto out_unlock;
+
+	chipnum = offset / MAX3191X_NGPIO;
+	if (max3191x_chip_is_faulting(max3191x, chipnum)) {
+		ret = -EIO;
+		goto out_unlock;
+	}
+
+	in = ((u8 *)max3191x->xfer.rx_buf)[chipnum * wordlen];
+	ret = (in >> (offset % MAX3191X_NGPIO)) & 1;
+
+out_unlock:
+	mutex_unlock(&max3191x->lock);
+	return ret;
+}
+
+static int max3191x_get_multiple(struct gpio_chip *gpio, unsigned long *mask,
+				 unsigned long *bits)
+{
+	struct max3191x_chip *max3191x = gpiochip_get_data(gpio);
+	int ret, bit = 0, wordlen = max3191x_wordlen(max3191x);
+
+	mutex_lock(&max3191x->lock);
+	ret = max3191x_readout_locked(max3191x);
+	if (ret)
+		goto out_unlock;
+
+	while ((bit = find_next_bit(mask, gpio->ngpio, bit)) != gpio->ngpio) {
+		unsigned int chipnum = bit / MAX3191X_NGPIO;
+		unsigned long in, shift, index;
+
+		if (max3191x_chip_is_faulting(max3191x, chipnum)) {
+			ret = -EIO;
+			goto out_unlock;
+		}
+
+		in = ((u8 *)max3191x->xfer.rx_buf)[chipnum * wordlen];
+		shift = round_down(bit % BITS_PER_LONG, MAX3191X_NGPIO);
+		index = bit / BITS_PER_LONG;
+		bits[index] &= ~(mask[index] & (0xff << shift));
+		bits[index] |= mask[index] & (in << shift); /* copy bits */
+
+		bit = (chipnum + 1) * MAX3191X_NGPIO; /* go to next chip */
+	}
+
+out_unlock:
+	mutex_unlock(&max3191x->lock);
+	return ret;
+}
+
+static int max3191x_set_config(struct gpio_chip *gpio, unsigned int offset,
+			       unsigned long config)
+{
+	struct max3191x_chip *max3191x = gpiochip_get_data(gpio);
+	u32 debounce, chipnum, db0_val, db1_val;
+
+	if (pinconf_to_config_param(config) != PIN_CONFIG_INPUT_DEBOUNCE)
+		return -ENOTSUPP;
+
+	if (!max3191x->db0_pins || !max3191x->db1_pins)
+		return -EINVAL;
+
+	debounce = pinconf_to_config_argument(config);
+	switch (debounce) {
+	case 0:
+		db0_val = 0;
+		db1_val = 0;
+		break;
+	case 1 ... 25:
+		db0_val = 0;
+		db1_val = 1;
+		break;
+	case 26 ... 750:
+		db0_val = 1;
+		db1_val = 0;
+		break;
+	case 751 ... 3000:
+		db0_val = 1;
+		db1_val = 1;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	if (max3191x->db0_pins->ndescs == 1)
+		chipnum = 0; /* all chips use the same pair of debounce pins */
+	else
+		chipnum = offset / MAX3191X_NGPIO; /* per chip debounce pins */
+
+	mutex_lock(&max3191x->lock);
+	gpiod_set_value_cansleep(max3191x->db0_pins->desc[chipnum], db0_val);
+	gpiod_set_value_cansleep(max3191x->db1_pins->desc[chipnum], db1_val);
+	mutex_unlock(&max3191x->lock);
+	return 0;
+}
+
+static void gpiod_set_array_single_value_cansleep(unsigned int ndescs,
+						  struct gpio_desc **desc,
+						  int value)
+{
+	int i, values[ndescs];
+
+	for (i = 0; i < ndescs; i++)
+		values[i] = value;
+
+	gpiod_set_array_value_cansleep(ndescs, desc, values);
+}
+
+static struct gpio_descs *devm_gpiod_get_array_optional_count(
+				struct device *dev, const char *con_id,
+				enum gpiod_flags flags, unsigned int expected)
+{
+	struct gpio_descs *descs;
+	int found = gpiod_count(dev, con_id);
+
+	if (found == -ENOENT)
+		return NULL;
+
+	if (found != expected && found != 1) {
+		dev_err(dev, "ignoring %s-gpios: found %d, expected %u or 1\n",
+			con_id, found, expected);
+		return NULL;
+	}
+
+	descs = devm_gpiod_get_array_optional(dev, con_id, flags);
+
+	if (IS_ERR(descs)) {
+		dev_err(dev, "failed to get %s-gpios: %ld\n",
+			con_id, PTR_ERR(descs));
+		return NULL;
+	}
+
+	return descs;
+}
+
+static int max3191x_probe(struct spi_device *spi)
+{
+	struct device *dev = &spi->dev;
+	struct max3191x_chip *max3191x;
+	int n, ret;
+
+	max3191x = devm_kzalloc(dev, sizeof(*max3191x), GFP_KERNEL);
+	if (!max3191x)
+		return -ENOMEM;
+	spi_set_drvdata(spi, max3191x);
+
+	max3191x->nchips = 1;
+	device_property_read_u32(dev, "#daisy-chained-devices",
+				 &max3191x->nchips);
+
+	n = BITS_TO_LONGS(max3191x->nchips);
+	max3191x->crc_error   = devm_kcalloc(dev, n, sizeof(long), GFP_KERNEL);
+	max3191x->undervolt1  = devm_kcalloc(dev, n, sizeof(long), GFP_KERNEL);
+	max3191x->undervolt2  = devm_kcalloc(dev, n, sizeof(long), GFP_KERNEL);
+	max3191x->overtemp    = devm_kcalloc(dev, n, sizeof(long), GFP_KERNEL);
+	max3191x->fault       = devm_kcalloc(dev, n, sizeof(long), GFP_KERNEL);
+	max3191x->xfer.rx_buf = devm_kcalloc(dev, max3191x->nchips,
+								2, GFP_KERNEL);
+	if (!max3191x->crc_error || !max3191x->undervolt1 ||
+	    !max3191x->overtemp  || !max3191x->undervolt2 ||
+	    !max3191x->fault     || !max3191x->xfer.rx_buf)
+		return -ENOMEM;
+
+	max3191x->modesel_pins = devm_gpiod_get_array_optional_count(dev,
+				 "maxim,modesel", GPIOD_ASIS, max3191x->nchips);
+	max3191x->fault_pins   = devm_gpiod_get_array_optional_count(dev,
+				 "maxim,fault", GPIOD_IN, max3191x->nchips);
+	max3191x->db0_pins     = devm_gpiod_get_array_optional_count(dev,
+				 "maxim,db0", GPIOD_OUT_LOW, max3191x->nchips);
+	max3191x->db1_pins     = devm_gpiod_get_array_optional_count(dev,
+				 "maxim,db1", GPIOD_OUT_LOW, max3191x->nchips);
+
+	max3191x->mode = device_property_read_bool(dev, "maxim,modesel-8bit")
+				 ? STATUS_BYTE_DISABLED : STATUS_BYTE_ENABLED;
+	if (max3191x->modesel_pins)
+		gpiod_set_array_single_value_cansleep(
+				 max3191x->modesel_pins->ndescs,
+				 max3191x->modesel_pins->desc, max3191x->mode);
+
+	max3191x->ignore_uv = device_property_read_bool(dev,
+						  "maxim,ignore-undervoltage");
+
+	if (max3191x->db0_pins && max3191x->db1_pins &&
+	    max3191x->db0_pins->ndescs != max3191x->db1_pins->ndescs) {
+		dev_err(dev, "ignoring maxim,db*-gpios: array len mismatch\n");
+		devm_gpiod_put_array(dev, max3191x->db0_pins);
+		devm_gpiod_put_array(dev, max3191x->db1_pins);
+		max3191x->db0_pins = NULL;
+		max3191x->db1_pins = NULL;
+	}
+
+	max3191x->xfer.len = max3191x->nchips * max3191x_wordlen(max3191x);
+	spi_message_init_with_transfers(&max3191x->mesg, &max3191x->xfer, 1);
+
+	max3191x->gpio.label = spi->modalias;
+	max3191x->gpio.owner = THIS_MODULE;
+	max3191x->gpio.parent = dev;
+	max3191x->gpio.base = -1;
+	max3191x->gpio.ngpio = max3191x->nchips * MAX3191X_NGPIO;
+	max3191x->gpio.can_sleep = true;
+
+	max3191x->gpio.get_direction = max3191x_get_direction;
+	max3191x->gpio.direction_input = max3191x_direction_input;
+	max3191x->gpio.direction_output = max3191x_direction_output;
+	max3191x->gpio.set = max3191x_set;
+	max3191x->gpio.set_multiple = max3191x_set_multiple;
+	max3191x->gpio.get = max3191x_get;
+	max3191x->gpio.get_multiple = max3191x_get_multiple;
+	max3191x->gpio.set_config = max3191x_set_config;
+
+	mutex_init(&max3191x->lock);
+
+	ret = gpiochip_add_data(&max3191x->gpio, max3191x);
+	if (ret) {
+		mutex_destroy(&max3191x->lock);
+		return ret;
+	}
+
+	return 0;
+}
+
+static int max3191x_remove(struct spi_device *spi)
+{
+	struct max3191x_chip *max3191x = spi_get_drvdata(spi);
+
+	gpiochip_remove(&max3191x->gpio);
+	mutex_destroy(&max3191x->lock);
+
+	return 0;
+}
+
+static int __init max3191x_register_driver(struct spi_driver *sdrv)
+{
+	crc8_populate_msb(max3191x_crc8, MAX3191X_CRC8_POLYNOMIAL);
+	return spi_register_driver(sdrv);
+}
+
+#ifdef CONFIG_OF
+static const struct of_device_id max3191x_of_id[] = {
+	{ .compatible = "maxim,max31910" },
+	{ .compatible = "maxim,max31911" },
+	{ .compatible = "maxim,max31912" },
+	{ .compatible = "maxim,max31913" },
+	{ .compatible = "maxim,max31953" },
+	{ .compatible = "maxim,max31963" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, max3191x_of_id);
+#endif
+
+static const struct spi_device_id max3191x_spi_id[] = {
+	{ "max31910" },
+	{ "max31911" },
+	{ "max31912" },
+	{ "max31913" },
+	{ "max31953" },
+	{ "max31963" },
+	{ }
+};
+MODULE_DEVICE_TABLE(spi, max3191x_spi_id);
+
+static struct spi_driver max3191x_driver = {
+	.driver = {
+		.name		= "max3191x",
+		.of_match_table	= of_match_ptr(max3191x_of_id),
+	},
+	.probe	  = max3191x_probe,
+	.remove	  = max3191x_remove,
+	.id_table = max3191x_spi_id,
+};
+module_driver(max3191x_driver, max3191x_register_driver, spi_unregister_driver);
+
+MODULE_AUTHOR("Lukas Wunner <lukas-JFq808J9C/izQB+pC5nmwQ@public.gmane.org>");
+MODULE_DESCRIPTION("GPIO driver for Maxim MAX3191x industrial serializer");
+MODULE_LICENSE("GPL v2");
-- 
2.11.0

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Re: [PATCH v2 0/5] GPIO driver for Maxim MAX3191x

[Linus Walleij]

On Thu, Oct 12, 2017 at 12:40 PM, Lukas Wunner <lukas@wunner.de> wrote:

> - Patch [1/5]: Change the argument order of assign_bit() to reflect
>   traditional "dst = src" in C. (Peter Zijlstra)
>
> - Patch [2/5]: Update documentation. (Linus Walleij)
>   Drop const qualifier from struct gpio_desc ** in all function
>   signatures to avoid a cast when passing a non-const array created
>   with gpiod_get_array(), which is likely the most common use case.

Applied these two so we get the infrastructure in place so others
can use it too.

> - Patch [3/5]: Newly inserted patch to introduce common property for
>   number of daisy-chained devices.
>
> - Patch [4/5]: Add vendor prefix to GPIO identifiers, use boolean
>   instead of integer to select mode, rename boolean to ignore
>   undervoltage alarms, separate compatible strings with newlines.
>   (Rob Herring)
>
> - Patch [5/5]: Optimize algorithm in max3191x_get_multiple() to
>   iterate over the bits in the mask, instead of iterating over every
>   chip, thus implicitly skipping chips which are not selected at all
>   by the mask.

These are pending device tree maintainer review.

Yours,
Linus Walleij

Re: [PATCH v2 3/5] dt-bindings: Document common property for daisy-chained devices

[Jonathan Cameron]

On Thu, 12 Oct 2017 12:40:10 +0200
Lukas Wunner <lukas-JFq808J9C/izQB+pC5nmwQ@public.gmane.org> wrote:

> Many serially-attached GPIO and IIO devices are daisy-chainable.
> 
>     Examples for GPIO devices are Maxim MAX3191x and TI SN65HVS88x:
>     https://datasheets.maximintegrated.com/en/ds/MAX31913.pdf
>     http://www.ti.com/lit/ds/symlink/sn65hvs880.pdf
> 
>     Examples for IIO devices are TI DAC128S085 and TI DAC161S055:
>     http://www.ti.com/lit/ds/symlink/dac128s085.pdf
>     http://www.ti.com/lit/ds/symlink/dac161s055.pdf
> 
> We already have drivers for daisy-chainable devices in the tree but
> their devicetree bindings are somewhat inconsistent and ill-named:
> 
>     The gpio-74x164.c driver uses "registers-number" to convey the
>     number of devices in the daisy-chain.  (Sans vendor prefix,
>     multiple vendors sell compatible versions of this chip.)
> 
>     The gpio-pisosr.c driver takes a different approach and calculates
>     the number of devices in the daisy-chain by dividing the common
>     "ngpios" property (Documentation/devicetree/bindings/gpio/gpio.txt)
>     by 8 (which assumes that each chip has 8 inputs).
> 
> Let's standardize on a common "#daisy-chained-devices" property.
> That name was chosen because it's the term most frequently used in
> datasheets.  (A less frequently used synonym is "cascaded devices".)
> 
> Signed-off-by: Lukas Wunner <lukas-JFq808J9C/izQB+pC5nmwQ@public.gmane.org>
Makes sense to me.
Acked-by: Jonathan Cameron <Jonathan.Cameron-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
> ---
> Changes v1 -> v2:
> 
> - Newly inserted patch.
> 
>  .../devicetree/bindings/common-properties.txt      | 26 ++++++++++++++++++++++
>  1 file changed, 26 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/common-properties.txt b/Documentation/devicetree/bindings/common-properties.txt
> index 697714f8d75c..a3448bfa1c82 100644
> --- a/Documentation/devicetree/bindings/common-properties.txt
> +++ b/Documentation/devicetree/bindings/common-properties.txt
> @@ -1,4 +1,8 @@
>  Common properties
> +=================
> +
> +Endianness
> +----------
>  
>  The Devicetree Specification does not define any properties related to hardware
>  byteswapping, but endianness issues show up frequently in porting Linux to
> @@ -58,3 +62,25 @@ dev: dev@40031000 {
>  	      ...
>  	      little-endian;
>  };
> +
> +Daisy-chained devices
> +---------------------
> +
> +Many serially-attached GPIO and IIO devices are daisy-chainable.  To the
> +host controller, a daisy-chain appears as a single device, but the number
> +of inputs and outputs it provides is the sum of inputs and outputs provided
> +by all of its devices.  The driver needs to know how many devices the
> +daisy-chain comprises to determine the amount of data exchanged, how many
> +inputs and outputs to register and so on.
> +
> +Optional properties:
> + - #daisy-chained-devices: Number of devices in the daisy-chain (default is 1).
> +
> +Example:
> +gpio@0 {
> +	      compatible = "name";
> +	      reg = <0>;
> +	      gpio-controller;
> +	      #gpio-cells = <2>;
> +	      #daisy-chained-devices = <3>;
> +};

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Re: [PATCH v2 4/5] dt-bindings: gpio: max3191x: Document new driver

[Rob Herring]

On Thu, Oct 12, 2017 at 12:40:10PM +0200, Lukas Wunner wrote:
> Add device tree bindings for Maxim MAX3191x industrial serializer.
> 
> Cc: Mathias Duckeck <m.duckeck@kunbus.de>
> Signed-off-by: Lukas Wunner <lukas@wunner.de>
> ---
> Changes v1 -> v2:
> 
> - Add vendor prefix to GPIO identifiers, use boolean instead of
>   integer to select mode, rename boolean to ignore undervoltage
>   alarms, separate compatible strings with newlines. (Rob Herring)
> 
>  .../devicetree/bindings/gpio/gpio-max3191x.txt     | 59 ++++++++++++++++++++++
>  1 file changed, 59 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/gpio/gpio-max3191x.txt

Acked-by: Rob Herring <robh@kernel.org>

Re: [PATCH v2 3/5] dt-bindings: Document common property for daisy-chained devices

[Rob Herring]

On Thu, Oct 12, 2017 at 12:40:10PM +0200, Lukas Wunner wrote:
> Many serially-attached GPIO and IIO devices are daisy-chainable.
> 
>     Examples for GPIO devices are Maxim MAX3191x and TI SN65HVS88x:
>     https://datasheets.maximintegrated.com/en/ds/MAX31913.pdf
>     http://www.ti.com/lit/ds/symlink/sn65hvs880.pdf
> 
>     Examples for IIO devices are TI DAC128S085 and TI DAC161S055:
>     http://www.ti.com/lit/ds/symlink/dac128s085.pdf
>     http://www.ti.com/lit/ds/symlink/dac161s055.pdf
> 
> We already have drivers for daisy-chainable devices in the tree but
> their devicetree bindings are somewhat inconsistent and ill-named:
> 
>     The gpio-74x164.c driver uses "registers-number" to convey the
>     number of devices in the daisy-chain.  (Sans vendor prefix,
>     multiple vendors sell compatible versions of this chip.)
> 
>     The gpio-pisosr.c driver takes a different approach and calculates
>     the number of devices in the daisy-chain by dividing the common
>     "ngpios" property (Documentation/devicetree/bindings/gpio/gpio.txt)
>     by 8 (which assumes that each chip has 8 inputs).
> 
> Let's standardize on a common "#daisy-chained-devices" property.
> That name was chosen because it's the term most frequently used in
> datasheets.  (A less frequently used synonym is "cascaded devices".)
> 
> Signed-off-by: Lukas Wunner <lukas-JFq808J9C/izQB+pC5nmwQ@public.gmane.org>
> ---
> Changes v1 -> v2:
> 
> - Newly inserted patch.
> 
>  .../devicetree/bindings/common-properties.txt      | 26 ++++++++++++++++++++++
>  1 file changed, 26 insertions(+)

Acked-by: Rob Herring <robh-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>

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Re: [PATCH v2 3/5] dt-bindings: Document common property for daisy-chained devices

[Linus Walleij]

On Thu, Oct 12, 2017 at 12:40 PM, Lukas Wunner <lukas-JFq808J9C/izQB+pC5nmwQ@public.gmane.org> wrote:

> Many serially-attached GPIO and IIO devices are daisy-chainable.
>
>     Examples for GPIO devices are Maxim MAX3191x and TI SN65HVS88x:
>     https://datasheets.maximintegrated.com/en/ds/MAX31913.pdf
>     http://www.ti.com/lit/ds/symlink/sn65hvs880.pdf
>
>     Examples for IIO devices are TI DAC128S085 and TI DAC161S055:
>     http://www.ti.com/lit/ds/symlink/dac128s085.pdf
>     http://www.ti.com/lit/ds/symlink/dac161s055.pdf
>
> We already have drivers for daisy-chainable devices in the tree but
> their devicetree bindings are somewhat inconsistent and ill-named:
>
>     The gpio-74x164.c driver uses "registers-number" to convey the
>     number of devices in the daisy-chain.  (Sans vendor prefix,
>     multiple vendors sell compatible versions of this chip.)
>
>     The gpio-pisosr.c driver takes a different approach and calculates
>     the number of devices in the daisy-chain by dividing the common
>     "ngpios" property (Documentation/devicetree/bindings/gpio/gpio.txt)
>     by 8 (which assumes that each chip has 8 inputs).
>
> Let's standardize on a common "#daisy-chained-devices" property.
> That name was chosen because it's the term most frequently used in
> datasheets.  (A less frequently used synonym is "cascaded devices".)
>
> Signed-off-by: Lukas Wunner <lukas-JFq808J9C/izQB+pC5nmwQ@public.gmane.org>
> ---
> Changes v1 -> v2:
>
> - Newly inserted patch.

Patch applied with the ACKs.

Yours,
Linus Walleij
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Re: [PATCH v2 4/5] dt-bindings: gpio: max3191x: Document new driver

[Linus Walleij]

On Thu, Oct 12, 2017 at 12:40 PM, Lukas Wunner <lukas-JFq808J9C/izQB+pC5nmwQ@public.gmane.org> wrote:

> Add device tree bindings for Maxim MAX3191x industrial serializer.
>
> Cc: Mathias Duckeck <m.duckeck-XB/JSsFECOqzQB+pC5nmwQ@public.gmane.org>
> Signed-off-by: Lukas Wunner <lukas-JFq808J9C/izQB+pC5nmwQ@public.gmane.org>
> ---
> Changes v1 -> v2:

Patch applied with Rob's ACK.

Yours,
Linus Walleij
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Re: [PATCH v2 5/5] gpio: Add driver for Maxim MAX3191x industrial serializer

[Linus Walleij]

On Thu, Oct 12, 2017 at 12:40 PM, Lukas Wunner <lukas@wunner.de> wrote:

> The driver was developed for and tested with the MAX31913 built into
> the Revolution Pi by KUNBUS, but should work with all members of the
> MAX3191x family:
>
> MAX31910: low power
> MAX31911: LED drivers
> MAX31912: LED drivers + 2nd voltage monitor + low power
> MAX31913: LED drivers + 2nd voltage monitor
> MAX31953: LED drivers + 2nd voltage monitor + isolation
> MAX31963: LED drivers + 2nd voltage monitor + isolation + buck regulator
>
> Cc: Mathias Duckeck <m.duckeck@kunbus.de>
> Signed-off-by: Lukas Wunner <lukas@wunner.de>

Patch applied.

Yours,
Linus Walleij