w1: w1-gpio: Convert to use GPIO descriptors

The w1 master driver includes a complete open drain emulation
reimplementation among other things.

This converts the driver and all board files using it to use
GPIO descriptors associated with the device to look up the
GPIO wire, as well ass the optional pull-up GPIO line.

When probed from the device tree, the driver will just pick
descriptors and use them right off. For the two board files
in the kernel, we add descriptor lookups so we do not need
to keep any old platform data handling around for the GPIO
lines.

As the platform data is also a state container for this driver,
we augment it to contain the GPIO descriptors.

w1_gpio_write_bit_dir() and w1_gpio_write_bit_val() are gone
since this pair was a reimplementation of open drain emulation
which is now handled by gpiolib.

The special "linux,open-drain" flag is a bit of mishap here:
it has the same semantic as the same flags in I2C: it means
that something in the platform is setting up the line as
open drain behind our back. We handle this the same way as
in I2C.

To drive the pull-up, we need to bypass open drain emulation
in gpiolib for the line, and this is done by driving it high
using gpiod_set_raw_value() which has been augmented to have
the semantic of overriding the open drain emulation.

We also augment the documentation to reflect the way to pass
GPIO descriptors from the machine.

Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

1 files changed, 14 insertions, 3 deletions

diff --git a/Documentation/w1/masters/w1-gpio b/Documentation/w1/masters/w1-gpio
index af5d3b4aa851..623961d9e83f 100644
--- a/Documentation/w1/masters/w1-gpio
+++ b/Documentation/w1/masters/w1-gpio
@@ -8,17 +8,27 @@ Description
 -----------
 
 GPIO 1-wire bus master driver. The driver uses the GPIO API to control the
-wire and the GPIO pin can be specified using platform data.
+wire and the GPIO pin can be specified using GPIO machine descriptor tables.
+It is also possible to define the master using device tree, see
+Documentation/devicetree/bindings/w1/w1-gpio.txt
 
 
 Example (mach-at91)
 -------------------
 
+#include <linux/gpio/machine.h>
 #include <linux/w1-gpio.h>
 
+static struct gpiod_lookup_table foo_w1_gpiod_table = {
+	.dev_id = "w1-gpio",
+	.table = {
+		GPIO_LOOKUP_IDX("at91-gpio", AT91_PIN_PB20, NULL, 0,
+			GPIO_ACTIVE_HIGH|GPIO_OPEN_DRAIN),
+	},
+};
+
 static struct w1_gpio_platform_data foo_w1_gpio_pdata = {
-	.pin		= AT91_PIN_PB20,
-	.is_open_drain	= 1,
+	.ext_pullup_enable_pin	= -EINVAL,
 };
 
 static struct platform_device foo_w1_device = {
@@ -30,4 +40,5 @@ static struct platform_device foo_w1_device = {
 ...
 	at91_set_GPIO_periph(foo_w1_gpio_pdata.pin, 1);
 	at91_set_multi_drive(foo_w1_gpio_pdata.pin, 1);
+	gpiod_add_lookup_table(&foo_w1_gpiod_table);
 	platform_device_register(&foo_w1_device);