[PATCH v5 0/2] gpio: Add gpio-latch driver

[PATCH v5 0/2] gpio: Add gpio-latch driver

[Sascha Hauer]

This series includes the changes requested by Serge Semin for v4.

Sascha

Sascha Hauer (2):
  gpio: Add gpio latch driver
  dt-bindings: gpio: Add gpio-latch binding document

 .../devicetree/bindings/gpio/gpio-latch.yaml  |  94 ++++++++
 drivers/gpio/Kconfig                          |   6 +
 drivers/gpio/Makefile                         |   1 +
 drivers/gpio/gpio-latch.c                     | 220 ++++++++++++++++++
 4 files changed, 321 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/gpio/gpio-latch.yaml
 create mode 100644 drivers/gpio/gpio-latch.c

-- 
2.30.2

[PATCH v5 1/2] gpio: Add gpio latch driver

[Sascha Hauer]

This driver implements a GPIO multiplexer based on latches connected to
other GPIOs. A set of data GPIOs is connected to the data input of
multiple latches. The clock input of each latch is driven by another
set of GPIOs. With two 8-bit latches 10 GPIOs can be multiplexed into
16 GPIOs. GPOs might be a better term as in fact the multiplexed pins
are output only.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
---

Notes:
    Changes since v4:
    - Use correct ndelay instead of udelay
    - Use #define for constant value
    - drop unnecessary delay
    
    Changes since v3:
    - Introduce delays between GPIO toggles as suggested by Serge Semin
    
    Changes since v2:
    - Fix inconsistent licensing
    - document locks
    - use regular bit operations
    - include linux/mod_devicetable.h rather than linux/of_device.h
    - Put spinlock and mutex into a union to make clear that only one of them is used
    - rename __gpio_latch_set to gpio_latch_set_unlocked
    
    Changes since v1:
    - Use gpiod_set_value_cansleep when the underlying GPIOs might sleep
    - Move MODULE_DEVICE_TABLE near to the end

 drivers/gpio/Kconfig      |   6 ++
 drivers/gpio/Makefile     |   1 +
 drivers/gpio/gpio-latch.c | 220 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 227 insertions(+)
 create mode 100644 drivers/gpio/gpio-latch.c

diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 0642f579196f2..e4603810ec910 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -1690,6 +1690,12 @@ config GPIO_AGGREGATOR
 	      industrial control context, to be operated from userspace using
 	      the GPIO chardev interface.
 
+config GPIO_LATCH
+	tristate "GPIO latch driver"
+	help
+	  Say yes here to enable a driver for GPIO multiplexers based on latches
+	  connected to other GPIOs.
+
 config GPIO_MOCKUP
 	tristate "GPIO Testing Driver"
 	select IRQ_SIM
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index a0985d30f51bb..310fa08decc69 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -75,6 +75,7 @@ obj-$(CONFIG_GPIO_IT87)			+= gpio-it87.o
 obj-$(CONFIG_GPIO_IXP4XX)		+= gpio-ixp4xx.o
 obj-$(CONFIG_GPIO_JANZ_TTL)		+= gpio-janz-ttl.o
 obj-$(CONFIG_GPIO_KEMPLD)		+= gpio-kempld.o
+obj-$(CONFIG_GPIO_LATCH)		+= gpio-latch.o
 obj-$(CONFIG_GPIO_LOGICVC)		+= gpio-logicvc.o
 obj-$(CONFIG_GPIO_LOONGSON1)		+= gpio-loongson1.o
 obj-$(CONFIG_GPIO_LOONGSON)		+= gpio-loongson.o
diff --git a/drivers/gpio/gpio-latch.c b/drivers/gpio/gpio-latch.c
new file mode 100644
index 0000000000000..24a8237b712b4
--- /dev/null
+++ b/drivers/gpio/gpio-latch.c
@@ -0,0 +1,220 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * GPIO latch driver
+ *
+ *  Copyright (C) 2022 Sascha Hauer <s.hauer@pengutronix.de>
+ *
+ * This driver implements a GPIO (or better GPO as there is no input)
+ * multiplexer based on latches like this:
+ *
+ * CLK0 ----------------------.        ,--------.
+ * CLK1 -------------------.  `--------|>    #0 |
+ *                         |           |        |
+ * OUT0 ----------------+--|-----------|D0    Q0|-----|<
+ * OUT1 --------------+-|--|-----------|D1    Q1|-----|<
+ * OUT2 ------------+-|-|--|-----------|D2    Q2|-----|<
+ * OUT3 ----------+-|-|-|--|-----------|D3    Q3|-----|<
+ * OUT4 --------+-|-|-|-|--|-----------|D4    Q4|-----|<
+ * OUT5 ------+-|-|-|-|-|--|-----------|D5    Q5|-----|<
+ * OUT6 ----+-|-|-|-|-|-|--|-----------|D6    Q6|-----|<
+ * OUT7 --+-|-|-|-|-|-|-|--|-----------|D7    Q7|-----|<
+ *        | | | | | | | |  |           `--------'
+ *        | | | | | | | |  |
+ *        | | | | | | | |  |           ,--------.
+ *        | | | | | | | |  `-----------|>    #1 |
+ *        | | | | | | | |              |        |
+ *        | | | | | | | `--------------|D0    Q0|-----|<
+ *        | | | | | | `----------------|D1    Q1|-----|<
+ *        | | | | | `------------------|D2    Q2|-----|<
+ *        | | | | `--------------------|D3    Q3|-----|<
+ *        | | | `----------------------|D4    Q4|-----|<
+ *        | | `------------------------|D5    Q5|-----|<
+ *        | `--------------------------|D6    Q6|-----|<
+ *        `----------------------------|D7    Q7|-----|<
+ *                                     `--------'
+ *
+ * The above is just an example. The actual number of number of latches and
+ * the number of inputs per latch is derived from the number of GPIOs given
+ * in the corresponding device tree properties.
+ */
+
+#include <linux/err.h>
+#include <linux/gpio/consumer.h>
+#include <linux/gpio/driver.h>
+#include <linux/module.h>
+#include <linux/mod_devicetable.h>
+#include <linux/platform_device.h>
+#include <linux/delay.h>
+
+#include "gpiolib.h"
+
+struct gpio_latch_priv {
+	struct gpio_chip gc;
+	struct gpio_descs *clk_gpios;
+	struct gpio_descs *latched_gpios;
+	int n_latched_gpios;
+	unsigned int setup_duration_ns;
+	unsigned int clock_duration_ns;
+	unsigned long *shadow;
+	/*
+	 * Depending on whether any of the underlying GPIOs may sleep we either
+	 * use a mutex or a spinlock to protect our shadow map.
+	 */
+	union {
+		struct mutex mutex; /* protects @shadow */
+		spinlock_t spinlock; /* protects @shadow */
+	};
+};
+
+static int gpio_latch_get_direction(struct gpio_chip *gc, unsigned int offset)
+{
+	return GPIO_LINE_DIRECTION_OUT;
+}
+
+static void gpio_latch_set_unlocked(struct gpio_latch_priv *priv,
+				    void (*set)(struct gpio_desc *desc, int value),
+				    unsigned int offset, bool val)
+{
+	int latch = offset / priv->n_latched_gpios;
+	int i;
+
+	assign_bit(offset, priv->shadow, val);
+
+	for (i = 0; i < priv->n_latched_gpios; i++)
+		set(priv->latched_gpios->desc[i],
+		    test_bit(latch * priv->n_latched_gpios + i, priv->shadow));
+
+	ndelay(priv->setup_duration_ns);
+	set(priv->clk_gpios->desc[latch], 1);
+	ndelay(priv->clock_duration_ns);
+	set(priv->clk_gpios->desc[latch], 0);
+}
+
+static void gpio_latch_set(struct gpio_chip *gc, unsigned int offset, int val)
+{
+	struct gpio_latch_priv *priv = gpiochip_get_data(gc);
+	unsigned long flags;
+
+	spin_lock_irqsave(&priv->spinlock, flags);
+
+	gpio_latch_set_unlocked(priv, gpiod_set_value, offset, val);
+
+	spin_unlock_irqrestore(&priv->spinlock, flags);
+}
+
+static void gpio_latch_set_can_sleep(struct gpio_chip *gc, unsigned int offset, int val)
+{
+	struct gpio_latch_priv *priv = gpiochip_get_data(gc);
+
+	mutex_lock(&priv->mutex);
+
+	gpio_latch_set_unlocked(priv, gpiod_set_value_cansleep, offset, val);
+
+	mutex_unlock(&priv->mutex);
+}
+
+static bool gpio_latch_can_sleep(struct gpio_latch_priv *priv, unsigned int n_latches)
+{
+	int i;
+
+	for (i = 0; i < n_latches; i++)
+		if (gpiod_cansleep(priv->clk_gpios->desc[i]))
+			return true;
+
+	for (i = 0; i < priv->n_latched_gpios; i++)
+		if (gpiod_cansleep(priv->latched_gpios->desc[i]))
+			return true;
+
+	return false;
+}
+
+/*
+ * Some value which is still acceptable to delay in atomic context.
+ * If we need to go higher we might have to switch to usleep_range(),
+ * but that cannot ne used in atomic context and the driver would have
+ * to be adjusted to support that.
+ */
+#define DURATION_NS_MAX 5000
+
+static int gpio_latch_probe(struct platform_device *pdev)
+{
+	struct gpio_latch_priv *priv;
+	unsigned int n_latches;
+	struct device_node *np = pdev->dev.of_node;
+
+	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->clk_gpios = devm_gpiod_get_array(&pdev->dev, "clk", GPIOD_OUT_LOW);
+	if (IS_ERR(priv->clk_gpios))
+		return PTR_ERR(priv->clk_gpios);
+
+	priv->latched_gpios = devm_gpiod_get_array(&pdev->dev, "latched", GPIOD_OUT_LOW);
+	if (IS_ERR(priv->latched_gpios))
+		return PTR_ERR(priv->latched_gpios);
+
+	n_latches = priv->clk_gpios->ndescs;
+	priv->n_latched_gpios = priv->latched_gpios->ndescs;
+
+	priv->shadow = devm_bitmap_zalloc(&pdev->dev, n_latches * priv->n_latched_gpios,
+					  GFP_KERNEL);
+	if (!priv->shadow)
+		return -ENOMEM;
+
+	if (gpio_latch_can_sleep(priv, n_latches)) {
+		priv->gc.can_sleep = true;
+		priv->gc.set = gpio_latch_set_can_sleep;
+		mutex_init(&priv->mutex);
+	} else {
+		priv->gc.can_sleep = false;
+		priv->gc.set = gpio_latch_set;
+		spin_lock_init(&priv->spinlock);
+	}
+
+	of_property_read_u32(np, "setup-duration-ns", &priv->setup_duration_ns);
+	if (priv->setup_duration_ns > DURATION_NS_MAX) {
+		dev_warn(&pdev->dev, "setup-duration-ns too high, limit to %d\n",
+			 DURATION_NS_MAX);
+		priv->setup_duration_ns = DURATION_NS_MAX;
+	}
+
+	of_property_read_u32(np, "clock-duration-ns", &priv->clock_duration_ns);
+	if (priv->clock_duration_ns > DURATION_NS_MAX) {
+		dev_warn(&pdev->dev, "clock-duration-ns too high, limit to %d\n",
+			 DURATION_NS_MAX);
+		priv->clock_duration_ns = DURATION_NS_MAX;
+	}
+
+	priv->gc.get_direction = gpio_latch_get_direction;
+	priv->gc.ngpio = n_latches * priv->n_latched_gpios;
+	priv->gc.owner = THIS_MODULE;
+	priv->gc.base = -1;
+	priv->gc.parent = &pdev->dev;
+
+	platform_set_drvdata(pdev, priv);
+
+	return devm_gpiochip_add_data(&pdev->dev, &priv->gc, priv);
+}
+
+static const struct of_device_id gpio_latch_ids[] = {
+	{
+		.compatible	= "gpio-latch",
+	}, {
+		/* sentinel */
+	}
+};
+MODULE_DEVICE_TABLE(of, gpio_latch_ids);
+
+static struct platform_driver gpio_latch_driver = {
+	.driver	= {
+		.name		= "gpio-latch",
+		.of_match_table	= gpio_latch_ids,
+	},
+	.probe	= gpio_latch_probe,
+};
+module_platform_driver(gpio_latch_driver);
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Sascha Hauer <s.hauer@pengutronix.de>");
+MODULE_DESCRIPTION("GPIO latch driver");
-- 
2.30.2

[PATCH v5 2/2] dt-bindings: gpio: Add gpio-latch binding document

[Sascha Hauer]

This adds a binding for a GPIO multiplexer driver based on latches
connected to other GPIOs.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Reviewed-by: Rob Herring <robh@kernel.org>
---

Notes:
    Changes since v3:
    - Introduce delays between GPIO toggles as suggested by Serge Semin
    
    Changes since v1:
    - Add license to binding file

 .../devicetree/bindings/gpio/gpio-latch.yaml  | 94 +++++++++++++++++++
 1 file changed, 94 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/gpio/gpio-latch.yaml

diff --git a/Documentation/devicetree/bindings/gpio/gpio-latch.yaml b/Documentation/devicetree/bindings/gpio/gpio-latch.yaml
new file mode 100644
index 0000000000000..1ed82a2cebdaa
--- /dev/null
+++ b/Documentation/devicetree/bindings/gpio/gpio-latch.yaml
@@ -0,0 +1,94 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/gpio/gpio-latch.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: GPIO latch controller
+
+maintainers:
+  - Sascha Hauer <s.hauer@pengutronix.de>
+
+description: |
+  This binding describes a GPIO multiplexer based on latches connected to
+  other GPIOs, like this:
+
+  CLK0 ----------------------.        ,--------.
+  CLK1 -------------------.  `--------|>    #0 |
+                          |           |        |
+  OUT0 ----------------+--|-----------|D0    Q0|-----|<
+  OUT1 --------------+-|--|-----------|D1    Q1|-----|<
+  OUT2 ------------+-|-|--|-----------|D2    Q2|-----|<
+  OUT3 ----------+-|-|-|--|-----------|D3    Q3|-----|<
+  OUT4 --------+-|-|-|-|--|-----------|D4    Q4|-----|<
+  OUT5 ------+-|-|-|-|-|--|-----------|D5    Q5|-----|<
+  OUT6 ----+-|-|-|-|-|-|--|-----------|D6    Q6|-----|<
+  OUT7 --+-|-|-|-|-|-|-|--|-----------|D7    Q7|-----|<
+         | | | | | | | |  |           `--------'
+         | | | | | | | |  |
+         | | | | | | | |  |           ,--------.
+         | | | | | | | |  `-----------|>    #1 |
+         | | | | | | | |              |        |
+         | | | | | | | `--------------|D0    Q0|-----|<
+         | | | | | | `----------------|D1    Q1|-----|<
+         | | | | | `------------------|D2    Q2|-----|<
+         | | | | `--------------------|D3    Q3|-----|<
+         | | | `----------------------|D4    Q4|-----|<
+         | | `------------------------|D5    Q5|-----|<
+         | `--------------------------|D6    Q6|-----|<
+         `----------------------------|D7    Q7|-----|<
+                                      `--------'
+
+  The number of clk-gpios and latched-gpios is not fixed. The actual number
+  of number of latches and the number of inputs per latch is derived from
+  the number of GPIOs given in the corresponding device tree properties.
+
+properties:
+  compatible:
+    const: gpio-latch
+  "#gpio-cells":
+    const: 2
+
+  clk-gpios:
+    description: Array of GPIOs to be used to clock a latch
+
+  latched-gpios:
+    description: Array of GPIOs to be used as inputs per latch
+
+  setup-duration-ns:
+    description: Delay in nanoseconds to wait after the latch inputs have been
+      set up
+
+  clock-duration-ns:
+    description: Delay in nanoseconds to wait between clock output changes
+
+  gpio-controller: true
+
+  gpio-line-names: true
+
+required:
+  - compatible
+  - "#gpio-cells"
+  - gpio-controller
+  - clk-gpios
+  - latched-gpios
+
+additionalProperties: false
+
+examples:
+  - |
+    gpio-latch {
+        #gpio-cells = <2>;
+        pinctrl-names = "default";
+        pinctrl-0 = <&pinctrl_di_do_leds>;
+        compatible = "gpio-latch";
+        gpio-controller;
+        setup-duration-ns = <100>;
+        clock-duration-ns = <100>;
+
+        clk-gpios = <&gpio3 7 0>, <&gpio3 8 0>;
+        latched-gpios = <&gpio3 21 0>, <&gpio3 22 0>,
+                       <&gpio3 23 0>, <&gpio3 24 0>,
+                       <&gpio3 25 0>, <&gpio3 26 0>,
+                       <&gpio3 27 0>, <&gpio3 28 0>;
+    };
-- 
2.30.2

Re: [PATCH v5 1/2] gpio: Add gpio latch driver

[Serge Semin]

On Fri, Oct 07, 2022 at 01:46:46PM +0200, Sascha Hauer wrote:
> This driver implements a GPIO multiplexer based on latches connected to
> other GPIOs. A set of data GPIOs is connected to the data input of
> multiple latches. The clock input of each latch is driven by another
> set of GPIOs. With two 8-bit latches 10 GPIOs can be multiplexed into
> 16 GPIOs. GPOs might be a better term as in fact the multiplexed pins
> are output only.
> 
> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

Reviewed-by: Serge Semin <fancer.lancer@gmail.com>

Please find a tiny nitpick below.

> ---
> 
> Notes:
>     Changes since v4:
>     - Use correct ndelay instead of udelay
>     - Use #define for constant value
>     - drop unnecessary delay
>     
>     Changes since v3:
>     - Introduce delays between GPIO toggles as suggested by Serge Semin
>     
>     Changes since v2:
>     - Fix inconsistent licensing
>     - document locks
>     - use regular bit operations
>     - include linux/mod_devicetable.h rather than linux/of_device.h
>     - Put spinlock and mutex into a union to make clear that only one of them is used
>     - rename __gpio_latch_set to gpio_latch_set_unlocked
>     
>     Changes since v1:
>     - Use gpiod_set_value_cansleep when the underlying GPIOs might sleep
>     - Move MODULE_DEVICE_TABLE near to the end
> 
>  drivers/gpio/Kconfig      |   6 ++
>  drivers/gpio/Makefile     |   1 +
>  drivers/gpio/gpio-latch.c | 220 ++++++++++++++++++++++++++++++++++++++
>  3 files changed, 227 insertions(+)
>  create mode 100644 drivers/gpio/gpio-latch.c
> 
> diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
> index 0642f579196f2..e4603810ec910 100644
> --- a/drivers/gpio/Kconfig
> +++ b/drivers/gpio/Kconfig
> @@ -1690,6 +1690,12 @@ config GPIO_AGGREGATOR
>  	      industrial control context, to be operated from userspace using
>  	      the GPIO chardev interface.
>  
> +config GPIO_LATCH
> +	tristate "GPIO latch driver"
> +	help
> +	  Say yes here to enable a driver for GPIO multiplexers based on latches
> +	  connected to other GPIOs.
> +
>  config GPIO_MOCKUP
>  	tristate "GPIO Testing Driver"
>  	select IRQ_SIM
> diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
> index a0985d30f51bb..310fa08decc69 100644
> --- a/drivers/gpio/Makefile
> +++ b/drivers/gpio/Makefile
> @@ -75,6 +75,7 @@ obj-$(CONFIG_GPIO_IT87)			+= gpio-it87.o
>  obj-$(CONFIG_GPIO_IXP4XX)		+= gpio-ixp4xx.o
>  obj-$(CONFIG_GPIO_JANZ_TTL)		+= gpio-janz-ttl.o
>  obj-$(CONFIG_GPIO_KEMPLD)		+= gpio-kempld.o
> +obj-$(CONFIG_GPIO_LATCH)		+= gpio-latch.o
>  obj-$(CONFIG_GPIO_LOGICVC)		+= gpio-logicvc.o
>  obj-$(CONFIG_GPIO_LOONGSON1)		+= gpio-loongson1.o
>  obj-$(CONFIG_GPIO_LOONGSON)		+= gpio-loongson.o
> diff --git a/drivers/gpio/gpio-latch.c b/drivers/gpio/gpio-latch.c
> new file mode 100644
> index 0000000000000..24a8237b712b4
> --- /dev/null
> +++ b/drivers/gpio/gpio-latch.c
> @@ -0,0 +1,220 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * GPIO latch driver
> + *
> + *  Copyright (C) 2022 Sascha Hauer <s.hauer@pengutronix.de>
> + *
> + * This driver implements a GPIO (or better GPO as there is no input)
> + * multiplexer based on latches like this:
> + *
> + * CLK0 ----------------------.        ,--------.
> + * CLK1 -------------------.  `--------|>    #0 |
> + *                         |           |        |
> + * OUT0 ----------------+--|-----------|D0    Q0|-----|<
> + * OUT1 --------------+-|--|-----------|D1    Q1|-----|<
> + * OUT2 ------------+-|-|--|-----------|D2    Q2|-----|<
> + * OUT3 ----------+-|-|-|--|-----------|D3    Q3|-----|<
> + * OUT4 --------+-|-|-|-|--|-----------|D4    Q4|-----|<
> + * OUT5 ------+-|-|-|-|-|--|-----------|D5    Q5|-----|<
> + * OUT6 ----+-|-|-|-|-|-|--|-----------|D6    Q6|-----|<
> + * OUT7 --+-|-|-|-|-|-|-|--|-----------|D7    Q7|-----|<
> + *        | | | | | | | |  |           `--------'
> + *        | | | | | | | |  |
> + *        | | | | | | | |  |           ,--------.
> + *        | | | | | | | |  `-----------|>    #1 |
> + *        | | | | | | | |              |        |
> + *        | | | | | | | `--------------|D0    Q0|-----|<
> + *        | | | | | | `----------------|D1    Q1|-----|<
> + *        | | | | | `------------------|D2    Q2|-----|<
> + *        | | | | `--------------------|D3    Q3|-----|<
> + *        | | | `----------------------|D4    Q4|-----|<
> + *        | | `------------------------|D5    Q5|-----|<
> + *        | `--------------------------|D6    Q6|-----|<
> + *        `----------------------------|D7    Q7|-----|<
> + *                                     `--------'
> + *
> + * The above is just an example. The actual number of number of latches and
> + * the number of inputs per latch is derived from the number of GPIOs given
> + * in the corresponding device tree properties.
> + */
> +
> +#include <linux/err.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/gpio/driver.h>
> +#include <linux/module.h>
> +#include <linux/mod_devicetable.h>
> +#include <linux/platform_device.h>
> +#include <linux/delay.h>
> +
> +#include "gpiolib.h"
> +
> +struct gpio_latch_priv {
> +	struct gpio_chip gc;
> +	struct gpio_descs *clk_gpios;
> +	struct gpio_descs *latched_gpios;
> +	int n_latched_gpios;
> +	unsigned int setup_duration_ns;
> +	unsigned int clock_duration_ns;
> +	unsigned long *shadow;
> +	/*
> +	 * Depending on whether any of the underlying GPIOs may sleep we either
> +	 * use a mutex or a spinlock to protect our shadow map.
> +	 */
> +	union {
> +		struct mutex mutex; /* protects @shadow */
> +		spinlock_t spinlock; /* protects @shadow */
> +	};
> +};
> +
> +static int gpio_latch_get_direction(struct gpio_chip *gc, unsigned int offset)
> +{
> +	return GPIO_LINE_DIRECTION_OUT;
> +}
> +
> +static void gpio_latch_set_unlocked(struct gpio_latch_priv *priv,
> +				    void (*set)(struct gpio_desc *desc, int value),
> +				    unsigned int offset, bool val)
> +{
> +	int latch = offset / priv->n_latched_gpios;
> +	int i;
> +
> +	assign_bit(offset, priv->shadow, val);
> +
> +	for (i = 0; i < priv->n_latched_gpios; i++)
> +		set(priv->latched_gpios->desc[i],
> +		    test_bit(latch * priv->n_latched_gpios + i, priv->shadow));
> +
> +	ndelay(priv->setup_duration_ns);
> +	set(priv->clk_gpios->desc[latch], 1);
> +	ndelay(priv->clock_duration_ns);
> +	set(priv->clk_gpios->desc[latch], 0);
> +}
> +
> +static void gpio_latch_set(struct gpio_chip *gc, unsigned int offset, int val)
> +{
> +	struct gpio_latch_priv *priv = gpiochip_get_data(gc);
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&priv->spinlock, flags);
> +
> +	gpio_latch_set_unlocked(priv, gpiod_set_value, offset, val);
> +
> +	spin_unlock_irqrestore(&priv->spinlock, flags);
> +}
> +
> +static void gpio_latch_set_can_sleep(struct gpio_chip *gc, unsigned int offset, int val)
> +{
> +	struct gpio_latch_priv *priv = gpiochip_get_data(gc);
> +
> +	mutex_lock(&priv->mutex);
> +
> +	gpio_latch_set_unlocked(priv, gpiod_set_value_cansleep, offset, val);
> +
> +	mutex_unlock(&priv->mutex);
> +}
> +
> +static bool gpio_latch_can_sleep(struct gpio_latch_priv *priv, unsigned int n_latches)
> +{
> +	int i;
> +
> +	for (i = 0; i < n_latches; i++)
> +		if (gpiod_cansleep(priv->clk_gpios->desc[i]))
> +			return true;
> +
> +	for (i = 0; i < priv->n_latched_gpios; i++)
> +		if (gpiod_cansleep(priv->latched_gpios->desc[i]))
> +			return true;
> +
> +	return false;
> +}
> +

> +/*
> + * Some value which is still acceptable to delay in atomic context.
> + * If we need to go higher we might have to switch to usleep_range(),
> + * but that cannot ne used in atomic context and the driver would have
> + * to be adjusted to support that.
> + */
> +#define DURATION_NS_MAX 5000

As I mentioned in v4 it would be better to place this above the struct
gpio_latch_priv declaration with the same comment. It's a common
practice to collect the macros in the head of the C-files above any
struct or forward declarations. But I guess @Linus or @Bartosz could
do that after merging the patch in if they find it's worth to be done.

-Sergey

> +
> +static int gpio_latch_probe(struct platform_device *pdev)
> +{
> +	struct gpio_latch_priv *priv;
> +	unsigned int n_latches;
> +	struct device_node *np = pdev->dev.of_node;
> +
> +	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
> +	if (!priv)
> +		return -ENOMEM;
> +
> +	priv->clk_gpios = devm_gpiod_get_array(&pdev->dev, "clk", GPIOD_OUT_LOW);
> +	if (IS_ERR(priv->clk_gpios))
> +		return PTR_ERR(priv->clk_gpios);
> +
> +	priv->latched_gpios = devm_gpiod_get_array(&pdev->dev, "latched", GPIOD_OUT_LOW);
> +	if (IS_ERR(priv->latched_gpios))
> +		return PTR_ERR(priv->latched_gpios);
> +
> +	n_latches = priv->clk_gpios->ndescs;
> +	priv->n_latched_gpios = priv->latched_gpios->ndescs;
> +
> +	priv->shadow = devm_bitmap_zalloc(&pdev->dev, n_latches * priv->n_latched_gpios,
> +					  GFP_KERNEL);
> +	if (!priv->shadow)
> +		return -ENOMEM;
> +
> +	if (gpio_latch_can_sleep(priv, n_latches)) {
> +		priv->gc.can_sleep = true;
> +		priv->gc.set = gpio_latch_set_can_sleep;
> +		mutex_init(&priv->mutex);
> +	} else {
> +		priv->gc.can_sleep = false;
> +		priv->gc.set = gpio_latch_set;
> +		spin_lock_init(&priv->spinlock);
> +	}
> +
> +	of_property_read_u32(np, "setup-duration-ns", &priv->setup_duration_ns);
> +	if (priv->setup_duration_ns > DURATION_NS_MAX) {
> +		dev_warn(&pdev->dev, "setup-duration-ns too high, limit to %d\n",
> +			 DURATION_NS_MAX);
> +		priv->setup_duration_ns = DURATION_NS_MAX;
> +	}
> +
> +	of_property_read_u32(np, "clock-duration-ns", &priv->clock_duration_ns);
> +	if (priv->clock_duration_ns > DURATION_NS_MAX) {
> +		dev_warn(&pdev->dev, "clock-duration-ns too high, limit to %d\n",
> +			 DURATION_NS_MAX);
> +		priv->clock_duration_ns = DURATION_NS_MAX;
> +	}
> +
> +	priv->gc.get_direction = gpio_latch_get_direction;
> +	priv->gc.ngpio = n_latches * priv->n_latched_gpios;
> +	priv->gc.owner = THIS_MODULE;
> +	priv->gc.base = -1;
> +	priv->gc.parent = &pdev->dev;
> +
> +	platform_set_drvdata(pdev, priv);
> +
> +	return devm_gpiochip_add_data(&pdev->dev, &priv->gc, priv);
> +}
> +
> +static const struct of_device_id gpio_latch_ids[] = {
> +	{
> +		.compatible	= "gpio-latch",
> +	}, {
> +		/* sentinel */
> +	}
> +};
> +MODULE_DEVICE_TABLE(of, gpio_latch_ids);
> +
> +static struct platform_driver gpio_latch_driver = {
> +	.driver	= {
> +		.name		= "gpio-latch",
> +		.of_match_table	= gpio_latch_ids,
> +	},
> +	.probe	= gpio_latch_probe,
> +};
> +module_platform_driver(gpio_latch_driver);
> +
> +MODULE_LICENSE("GPL v2");
> +MODULE_AUTHOR("Sascha Hauer <s.hauer@pengutronix.de>");
> +MODULE_DESCRIPTION("GPIO latch driver");
> -- 
> 2.30.2
> 

Re: [PATCH v5 2/2] dt-bindings: gpio: Add gpio-latch binding document

[Serge Semin]

On Fri, Oct 07, 2022 at 01:46:47PM +0200, Sascha Hauer wrote:
> This adds a binding for a GPIO multiplexer driver based on latches
> connected to other GPIOs.
> 
> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> Reviewed-by: Rob Herring <robh@kernel.org>

Reviewed-by: Serge Semin <fancer.lancer@gmail.com>

Just a note. In accordance with [1] the DT-bindings patches should come
in the series before the code implementing the bindings.

[1] Documentation/devicetree/bindings/submitting-patches.rst, unit I.5).

-Sergey

> ---
> 
> Notes:
>     Changes since v3:
>     - Introduce delays between GPIO toggles as suggested by Serge Semin
>     
>     Changes since v1:
>     - Add license to binding file
> 
>  .../devicetree/bindings/gpio/gpio-latch.yaml  | 94 +++++++++++++++++++
>  1 file changed, 94 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/gpio/gpio-latch.yaml
> 
> diff --git a/Documentation/devicetree/bindings/gpio/gpio-latch.yaml b/Documentation/devicetree/bindings/gpio/gpio-latch.yaml
> new file mode 100644
> index 0000000000000..1ed82a2cebdaa
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/gpio/gpio-latch.yaml
> @@ -0,0 +1,94 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/gpio/gpio-latch.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: GPIO latch controller
> +
> +maintainers:
> +  - Sascha Hauer <s.hauer@pengutronix.de>
> +
> +description: |
> +  This binding describes a GPIO multiplexer based on latches connected to
> +  other GPIOs, like this:
> +
> +  CLK0 ----------------------.        ,--------.
> +  CLK1 -------------------.  `--------|>    #0 |
> +                          |           |        |
> +  OUT0 ----------------+--|-----------|D0    Q0|-----|<
> +  OUT1 --------------+-|--|-----------|D1    Q1|-----|<
> +  OUT2 ------------+-|-|--|-----------|D2    Q2|-----|<
> +  OUT3 ----------+-|-|-|--|-----------|D3    Q3|-----|<
> +  OUT4 --------+-|-|-|-|--|-----------|D4    Q4|-----|<
> +  OUT5 ------+-|-|-|-|-|--|-----------|D5    Q5|-----|<
> +  OUT6 ----+-|-|-|-|-|-|--|-----------|D6    Q6|-----|<
> +  OUT7 --+-|-|-|-|-|-|-|--|-----------|D7    Q7|-----|<
> +         | | | | | | | |  |           `--------'
> +         | | | | | | | |  |
> +         | | | | | | | |  |           ,--------.
> +         | | | | | | | |  `-----------|>    #1 |
> +         | | | | | | | |              |        |
> +         | | | | | | | `--------------|D0    Q0|-----|<
> +         | | | | | | `----------------|D1    Q1|-----|<
> +         | | | | | `------------------|D2    Q2|-----|<
> +         | | | | `--------------------|D3    Q3|-----|<
> +         | | | `----------------------|D4    Q4|-----|<
> +         | | `------------------------|D5    Q5|-----|<
> +         | `--------------------------|D6    Q6|-----|<
> +         `----------------------------|D7    Q7|-----|<
> +                                      `--------'
> +
> +  The number of clk-gpios and latched-gpios is not fixed. The actual number
> +  of number of latches and the number of inputs per latch is derived from
> +  the number of GPIOs given in the corresponding device tree properties.
> +
> +properties:
> +  compatible:
> +    const: gpio-latch
> +  "#gpio-cells":
> +    const: 2
> +
> +  clk-gpios:
> +    description: Array of GPIOs to be used to clock a latch
> +
> +  latched-gpios:
> +    description: Array of GPIOs to be used as inputs per latch
> +
> +  setup-duration-ns:
> +    description: Delay in nanoseconds to wait after the latch inputs have been
> +      set up
> +
> +  clock-duration-ns:
> +    description: Delay in nanoseconds to wait between clock output changes
> +
> +  gpio-controller: true
> +
> +  gpio-line-names: true
> +
> +required:
> +  - compatible
> +  - "#gpio-cells"
> +  - gpio-controller
> +  - clk-gpios
> +  - latched-gpios
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    gpio-latch {
> +        #gpio-cells = <2>;
> +        pinctrl-names = "default";
> +        pinctrl-0 = <&pinctrl_di_do_leds>;
> +        compatible = "gpio-latch";
> +        gpio-controller;
> +        setup-duration-ns = <100>;
> +        clock-duration-ns = <100>;
> +
> +        clk-gpios = <&gpio3 7 0>, <&gpio3 8 0>;
> +        latched-gpios = <&gpio3 21 0>, <&gpio3 22 0>,
> +                       <&gpio3 23 0>, <&gpio3 24 0>,
> +                       <&gpio3 25 0>, <&gpio3 26 0>,
> +                       <&gpio3 27 0>, <&gpio3 28 0>;
> +    };
> -- 
> 2.30.2
> 

Re: [PATCH v5 1/2] gpio: Add gpio latch driver

[Linus Walleij]

On Fri, Oct 7, 2022 at 1:47 PM Sascha Hauer <s.hauer@pengutronix.de> wrote:

> This driver implements a GPIO multiplexer based on latches connected to
> other GPIOs. A set of data GPIOs is connected to the data input of
> multiple latches. The clock input of each latch is driven by another
> set of GPIOs. With two 8-bit latches 10 GPIOs can be multiplexed into
> 16 GPIOs. GPOs might be a better term as in fact the multiplexed pins
> are output only.
>
> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

This looks fine to me!
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>

Yours,
Linus Walleij

Re: [PATCH v5 2/2] dt-bindings: gpio: Add gpio-latch binding document

[Linus Walleij]

On Fri, Oct 7, 2022 at 1:47 PM Sascha Hauer <s.hauer@pengutronix.de> wrote:

> This adds a binding for a GPIO multiplexer driver based on latches
> connected to other GPIOs.
>
> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> Reviewed-by: Rob Herring <robh@kernel.org>

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>

Yours,
Linus Walleij

Re: [PATCH v5 0/2] gpio: Add gpio-latch driver

[Bartosz Golaszewski]

On Fri, Oct 7, 2022 at 1:47 PM Sascha Hauer <s.hauer@pengutronix.de> wrote:
>
> This series includes the changes requested by Serge Semin for v4.
>
> Sascha
>
> Sascha Hauer (2):
>   gpio: Add gpio latch driver
>   dt-bindings: gpio: Add gpio-latch binding document
>
>  .../devicetree/bindings/gpio/gpio-latch.yaml  |  94 ++++++++
>  drivers/gpio/Kconfig                          |   6 +
>  drivers/gpio/Makefile                         |   1 +
>  drivers/gpio/gpio-latch.c                     | 220 ++++++++++++++++++
>  4 files changed, 321 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/gpio/gpio-latch.yaml
>  create mode 100644 drivers/gpio/gpio-latch.c
>
> --
> 2.30.2
>

I reversed the order of the patches, fixed the strange formatting of
struct of_device_id and queued the series.

Bartosz