Commit graph

5 commits

Author SHA1 Message Date
Linus Walleij
e0fc62a655 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>
2017-12-08 15:32:53 +01:00
Evgeny Boger
3089a4c8d3 drivers/w1/masters/w1-gpio.c: add strong pullup emulation
Strong pullup is emulated by driving pin logic high after write command
when using tri-state push-pull GPIO.

Signed-off-by: Evgeny Boger <boger@contactless.ru>
Cc: Greg KH <greg@kroah.com>
Acked-by: David Fries <david@fries.net>
Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-01-23 16:37:04 -08:00
Daniel Mack
d2323cf773 onewire: w1-gpio: add ext_pullup_enable pin in platform data
In the process of porting boards to devicetree implemenation, we should
keep information about external circuitry where they belong - the
individual drivers.

This patch adds a way to specify a GPIO to drive the (optional) external
pull-up logic, rather than using a function pointer for that.

Signed-off-by: Daniel Mack <zonque@gmail.com>
Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Acked-by: Ville Syrjälä <syrjala@sci.fi>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-08-16 10:02:33 -07:00
Daniel Mack
c8a06c1ef0 w1-gpio: add external pull-up enable callback
On embedded devices, sleep mode conditions can be tricky to handle,
Especially when processors tend to pull-down the w1 bus during sleep.  Bus
slaves (such as the ds2760) may interpret this as a reason for power-down
conditions and entirely switch off the device.

This patch adds a callback function pointer to let users switch on and off
the external pull-up resistor.  This lets the outside world know whether
the processor is currently actively driving the bus or not.

When this callback is not provided, the code behaviour won't change.

Signed-off-by: Daniel Mack <daniel@caiaq.de>
Acked-by: Ville Syrjala <syrjala@sci.fi>
Acked-by: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-06-18 13:03:58 -07:00
Ville Syrjala
ad8dc96e3b w1-gpio: add GPIO w1 bus master driver
Add a GPIO 1-wire bus master driver.  The driver used the GPIO API to
control the wire and the GPIO pin can be specified using platform data
similar to i2c-gpio.  The driver was tested with AT91SAM9260 + DS2401.

Signed-off-by: Ville Syrjala <syrjala@sci.fi>
Cc: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-06 10:41:15 -08:00