gpio: Enable pcf857x GPIO expander for Device Tree

Add code to parse the GPIO expander Device Tree node and extract platform data out of it, and populate the struct 'pcf857x_platform_data' maintained by the driver. This enables devices to reference the gpio expander from Device Tree.

Add DT binding info in Documentation.

CC Grant Likely <[email protected]>

Signed-off-by Archit Taneja <[email protected]>

---
  .../devicetree/bindings/gpio/gpio-pcf857x.txt      | 44 +++++++++++++++++
  drivers/gpio/gpio-pcf857x.c                        | 57 ++++++++++++++++++++--
  2 files changed, 97 insertions(+), 4 deletions(-)

create mode 100644 Documentation/devicetree/bindings/gpio/gpio-pcf857x.txt

Documentation/devicetree/bindings/gpio/gpio-pcf857x.txt new file +44 -0

new file mode 100644
index 0000000..0556512
@@ -0,0 +1,44 @@
+PCF857x I2C based GPIO controller bindings
+
+Required properties:
+- compatible:
+  - "nxp,pca9670" for NXP PCA9670 8 bit I/O expander
+  - "nxp,pca9672" for NXP PCA9672 8 bit I/O expander with interrupt
+  - "nxp,pca9674" for NXP PCA9672 8 bit I/O expander with interrupt
+  - "nxp,pca8574" for NXP PCA8574 8 bit I/O expander with interrupt
+  - "nxp,pca8575" for NXP PCA8575 16 bit I/O expander with interrupt
+  - "nxp,pca9671" for NXP PCA9671 16 bit I/O expander
+  - "nxp,pca9673" for NXP PCA9673 16 bit I/O expander with interrupt
+  - "nxp,pca9675" for NXP PCA9675 16 bit I/O expander with interrupt
+  - "ti,pcf8574"  for TI PCF8574 8 bit I/O expander with interrupt
+  - "ti,pcf8574a" for TI PCF8574A 8 bit I/O expander with interrupt
+  - "ti,pcf8575"  for TI PCF8575 16 bit I/O expander with interrupt
+  - "ti,tca9554"  for TI TCA9554 8 bit I/O expander with interrupt
+  - "maxim,max7328" for MAXIM MAX7328 8 bit I/O expander with interrupt
+  - "maxim,max7329" for MAXIM MAX7329 8 bit I/O expander with interrupt
+- gpio-controller : Marks the device node as a GPIO controller.
+- #gpio-cells : Should be two.
+  - first cell is the pin number.
+  - second cell is unused.
+- interrupt-controller: Mark the device node as an interrupt controller.
+- #interrupt-cells : Should be two.
+  - first cell is the GPIO number.
+  - second cell is unused.
+- reg: I2C address of the chip.
+
+Device speific properties:
+- n_latch:		optional bit-inverse of initial register value; if
+			you leave this initialized to zero the driver will act
+			like the chip was just reset.
+
+Example:
+
+pcf8575: pcf8575 {
+	compatible = "ti,pcf8575";
+	gpio-controller;
+	#gpio-cells = <2>;
+	interrupt-controller;
+	#interrupt-cells = <2>;
+	reg = <0x20>;
+	n_latch = <0x0>;
+};

drivers/gpio/gpio-pcf857x.c +53 -4

index e8faf53..3435790 100644
@@ -21,6 +21,7 @@
  #include <linux/kernel.h>
  #include <linux/slab.h>
  #include <linux/gpio.h>
+#include <linux/of.h>
  #include <linux/i2c.h>
  #include <linux/i2c/pcf857x.h>
  #include <linux/interrupt.h>

@@ -255,17 +256,42 @@ fail:
 
  /*-------------------------------------------------------------------------*/
 
+static struct pcf857x_platform_data *of_gpio_pcf857x(struct device *dev)
+{
+	struct pcf857x_platform_data *pdata;
+	int r;
+
+	pdata = devm_kzalloc(dev, sizeof(*pdata), GFP_KERNEL);
+	if (!pdata)
+		return NULL;
+
+	pdata->gpio_base = -1;
+
+	r = of_property_read_u32(dev->of_node, "n_latch", &pdata->n_latch);
+	if (r) {
+		dev_dbg(dev, "couldn't find n-latch, use default\n");
+		pdata->n_latch = 0;
+	}
+
+	return pdata;
+}
+
  static int pcf857x_probe(struct i2c_client *client,
  			 const struct i2c_device_id *id)
  {
  	struct pcf857x_platform_data	*pdata;
+	struct device_node		*node;
  	struct pcf857x			*gpio;
  	int				status;
 
  	pdata = client->dev.platform_data;
-	if (!pdata) {
+	node = client->dev.of_node;
+
+	if (!pdata && node)
+		pdata = of_gpio_pcf857x(&client->dev);
+
+	if (!pdata)
  		dev_dbg(&client->dev, "no platform data\n");
-	}
 
  	/* Allocate, initialize, and register this gpio_chip. */
  	gpio = devm_kzalloc(&client->dev, sizeof(*gpio), GFP_KERNEL);

@@ -420,10 +446,33 @@ static int pcf857x_remove(struct i2c_client *client)
  	return status;
  }
 
+static const struct of_device_id pcf857x_dt_ids[] = {
+	{ .compatible = "nxp,pca9670", },
+	{ .compatible = "nxp,pca9672", },
+	{ .compatible = "nxp,pca9674", },
+	{ .compatible = "nxp,pca8574", },
+	{ .compatible = "nxp,pca8575", },
+	{ .compatible = "nxp,pca9671", },
+	{ .compatible = "nxp,pca9673", },
+	{ .compatible = "nxp,pca9675", },
+
+	{ .compatible = "ti,pcf8574", },
+	{ .compatible = "ti,pcf8574a", },
+	{ .compatible = "ti,pcf8575", },
+	{ .compatible = "ti,tca9554", },
+
+	{ .compatible = "maxim,max7328", },
+	{ .compatible = "maxim,max7329", },
+	{ }
+};
+
+MODULE_DEVICE_TABLE(of, pcf857x_dt_ids);
+
  static struct i2c_driver pcf857x_driver = {
  	.driver = {
-		.name	= "pcf857x",
-		.owner	= THIS_MODULE,
+		.name		= "pcf857x",
+		.owner		= THIS_MODULE,
+		.of_match_table	= pcf857x_dt_ids,
  	},
  	.probe	= pcf857x_probe,
  	.remove	= pcf857x_remove,

Add code to parse the GPIO expander Device Tree node and extract platform data out of it, and populate the struct 'pcf857x_platform_data' maintained by the driver. This enables devices to reference the gpio expander from Device Tree.

Add DT binding info in Documentation.

CC Grant Likely <[email protected]>

Signed-off-by Archit Taneja <[email protected]>

+++ b/Documentation/devicetree/bindings/gpio/gpio-pcf857x.txt

Documentation/devicetree/bindings/gpio/gpio-pcf857x.txt new file +12 -0

@@ -0,0 +1,44 @@
+PCF857x I2C based GPIO controller bindings
+
+Required properties:
+- compatible:
+  - "nxp,pca9670" for NXP PCA9670 8 bit I/O expander
+  - "nxp,pca9672" for NXP PCA9672 8 bit I/O expander with interrupt
+  - "nxp,pca9674" for NXP PCA9672 8 bit I/O expander with interrupt
+  - "nxp,pca8574" for NXP PCA8574 8 bit I/O expander with interrupt
+  - "nxp,pca8575" for NXP PCA8575 16 bit I/O expander with interrupt
+  - "nxp,pca9671" for NXP PCA9671 16 bit I/O expander
+  - "nxp,pca9673" for NXP PCA9673 16 bit I/O expander with interrupt
+  - "nxp,pca9675" for NXP PCA9675 16 bit I/O expander with interrupt

Quoted 8 lines · Archit Taneja

Add code to parse the GPIO expander Device Tree node and extract platform data out of it, and populate the struct 'pcf857x_platform_data' maintained by the driver. This enables devices to reference the gpio expander from Device Tree.

Add DT binding info in Documentation.

CC Grant Likely <[email protected]>

Signed-off-by Archit Taneja <[email protected]>

(...)

Quoted 19 lines

+++ b/Documentation/devicetree/bindings/gpio/gpio-pcf857x.txt

Documentation/devicetree/bindings/gpio/gpio-pcf857x.txt new file +17 -0

@@ -0,0 +1,44 @@
+PCF857x I2C based GPIO controller bindings
+
+Required properties:
+- compatible:
+  - "nxp,pca9670" for NXP PCA9670 8 bit I/O expander
+  - "nxp,pca9672" for NXP PCA9672 8 bit I/O expander with interrupt
+  - "nxp,pca9674" for NXP PCA9672 8 bit I/O expander with interrupt
+  - "nxp,pca8574" for NXP PCA8574 8 bit I/O expander with interrupt
+  - "nxp,pca8575" for NXP PCA8575 16 bit I/O expander with interrupt
+  - "nxp,pca9671" for NXP PCA9671 16 bit I/O expander
+  - "nxp,pca9673" for NXP PCA9673 16 bit I/O expander with interrupt
+  - "nxp,pca9675" for NXP PCA9675 16 bit I/O expander with interrupt
+  - "ti,pcf8574"  for TI PCF8574 8 bit I/O expander with interrupt
+  - "ti,pcf8574a" for TI PCF8574A 8 bit I/O expander with interrupt
+  - "ti,pcf8575"  for TI PCF8575 16 bit I/O expander with interrupt
+  - "ti,tca9554"  for TI TCA9554 8 bit I/O expander with interrupt
+  - "maxim,max7328" for MAXIM MAX7328 8 bit I/O expander with interrupt

Documentation/devicetree/bindings/gpio/gpio-pcf857x.txt line 22

Quoted 5 lines

Documentation/devicetree/bindings/gpio/gpio-pcf857x.txt new file +5 -0

+  - "maxim,max7329" for MAXIM MAX7329 8 bit I/O expander with interrupt
+- gpio-controller : Marks the device node as a GPIO controller.
+- #gpio-cells : Should be two.
+  - first cell is the pin number.
+  - second cell is unused.

I guess you're adding this because the generic GPIO bindings use it and of_gpio_simple_xlate() depends on this two-cell layout.

Make a reference to the generic GPIO bindings and note that the second cell is *NOT* unused, as it is used in the GPIOlib!

Documentation/devicetree/bindings/gpio/gpio-pcf857x.txt line 25

Quoted 4 lines

Documentation/devicetree/bindings/gpio/gpio-pcf857x.txt new file +3 -0

+- interrupt-controller: Mark the device node as an interrupt controller.
+- #interrupt-cells : Should be two.
+  - first cell is the GPIO number.

Surely it is the IRQ number and not the GPIO number. The fact that the IRQ originates in a GPIO controller does not matter.

Review line 26

Quoted 2 lines

(quoted diff) +1 -0

+  - second cell is unused.

So why do you add it? Usually this is used for trigger flags. Are you planning to add this later, i.e. does the chip support this, and if it doesn't then get rid of this flag.

Documentation/devicetree/bindings/gpio/gpio-pcf857x.txt line 32

Quoted 7 lines

Documentation/devicetree/bindings/gpio/gpio-pcf857x.txt new file +6 -0

+- reg: I2C address of the chip.
+
+Device speific properties:
+- n_latch:             optional bit-inverse of initial register value; if
+                       you leave this initialized to zero the driver will act
+                       like the chip was just reset.

Explain what happens if you do *not* leave it as zero and what the bits mean in that case.

On Monday 17 June 2013 02:35 PM, Linus Walleij wrote:

Just a query, there is an example in gpio.txt in the gpio bindings documentation which sets #gpio-cells as 1. Is this is a wrong example, or are 1 cell gpio controllers valid?

About this chip, a change in any of it's GPIOs configured as inputs will generate an interrupt, then it's up to the driver to figure out which GPIOs changed and handle their corresponding irqs. So shouldn't a device connected to the chip describe the gpio number within the pcf857x chip as it's first cell?

I've made a hypothetical example of a pcf8575 chip, which has it's interrupt line connected to an omap gpio, and pcf8575's 7th gpio is connected to 'pcf_slave'. The pcf_slave's driver requests for an interrupt. Is this the correct way to describe this? :

pcf: pcf8575@23 {
        compatible = "ti,pcf8575";
        reg = <0x23>;
        gpio-controller;
        #gpio-cells = <2>;
        #interrupt-controller;
        #interrupt-cells = <1>;
        interrupt-parent = <&gpio2>;    /* an omap gpio bank */
        interrupts = <2 8>;             /* gpio line 34, low triggered*/
};

pcf_slave: slave {
        ...
        ...
        #interrupt-parent = <&pcf>;
        interrupts = <7>;       /* connected to 7th IO pin of pcf857x*/
};

drivers/gpio/gpio-pcf857x.c fail: · line 264

Quoted 6 lines · Archit Taneja

drivers/gpio/gpio-pcf857x.c +6 -0

+static struct pcf857x_platform_data *of_gpio_pcf857x(struct device *dev)
+{
+       struct pcf857x_platform_data *pdata;
+       int r;
+
+       pdata = devm_kzalloc(dev, sizeof(*pdata), GFP_KERNEL);

This memory is never freed, is it?

Add code to parse the GPIO expander Device Tree node and extract platform data out of it, and populate the struct 'pcf857x_platform_data' maintained by the driver. This enables devices to reference the gpio expander from Device Tree.

Add DT binding info in Documentation.

Signed-off-by Archit Taneja <[email protected]>

---
- v2 posted after quite a while, sorry for the delay!

Changes in v2:
- second gpeio-cell description corrected in Documentation
- interrupt controller description removed for now, will be added in a follow up patch
- n_latch description updated

Quoted 11 lines · Archit Taneja

Add code to parse the GPIO expander Device Tree node and extract platform data out of it, and populate the struct 'pcf857x_platform_data' maintained by the driver. This enables devices to reference the gpio expander from Device Tree.

Add DT binding info in Documentation.

Signed-off-by Archit Taneja <[email protected]>

---
- v2 posted after quite a while, sorry for the delay!

Quoted 5 lines

Changes in v2:
- second gpeio-cell description corrected in Documentation
- interrupt controller description removed for now, will be added in a follow up patch
- n_latch description updated

The devicetree portions of this patch needs to be reviewed by devicetree at vger.kernel.org, so please repost including that list.

Quoted 12 lines · On Tuesday 27 August 2013 05:20:45 Linus Walleij wrote:

Quoted 11 lines · Archit Taneja

Add code to parse the GPIO expander Device Tree node and extract platform data out of it, and populate the struct 'pcf857x_platform_data' maintained by the driver. This enables devices to reference the gpio expander from Device Tree.

Add DT binding info in Documentation.

Signed-off-by Archit Taneja <[email protected]>

---
- v2 posted after quite a while, sorry for the delay!

Quoted 5 lines

Quoted 5 lines

Changes in v2:
- second gpeio-cell description corrected in Documentation
- interrupt controller description removed for now, will be added in a follow up patch
- n_latch description updated

And it seems that the patch conflicts with

https://lkml.org/lkml/2013/8/26/248

:-/

If we end up merging this one, I'd like to at least rename the DT n-latch property to pin-initial-states as in my patch and update the documentation, as I find it more explicit.

Quoted 20 lines · Laurent Pinchart

Quoted 19 lines · On Tuesday 27 August 2013 05:20:45 Linus Walleij wrote:

Quoted 18 lines · Archit Taneja

Add code to parse the GPIO expander Device Tree node and extract platform
data out of it, and populate the struct 'pcf857x_platform_data' maintained by the driver. This enables devices to reference the gpio expander from Device Tree.

Add DT binding info in Documentation.

Signed-off-by Archit Taneja <[email protected]>

---
- v2 posted after quite a while, sorry for the delay!

Changes in v2:
- second gpeio-cell description corrected in Documentation
- interrupt controller description removed for now, will be added in a

follow up patch

Quoted 7 lines

Quoted 1 line

Quoted 1 line

- n_latch description updated

And it seems that the patch conflicts with

https://lkml.org/lkml/2013/8/26/248

:-/

:/

Quoted 3 lines

If we end up merging this one, I'd like to at least rename the DT n-latch property to pin-initial-states as in my patch and update the documentation, as I find it more explicit.

I think your patch is cleaner and more descriptive.

The only thing which I am not clear about in your patch is the extra work done in getting ngpio, that should be available in i2c_device_id pointer argument in probe(id points to the array pcf857x_id already available in the driver with the number of gpios for each chip variant).