pinconf-generic: add BIAS_BUS_HOLD pinconf

Add a new PIN_CONFIG_BIAS_BUS_HOLD pin configuration for a bus holder
pin mode (also known as bus keeper, or repeater). This is a weak latch
which drives the last value on a tristate bus. Another device on the bus
can drive the bus high or low before going tristate to change the value
driven by the pin.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/include/linux/pinctrl/pinconf-generic.h b/include/linux/pinctrl/pinconf-generic.h
index 6aa238096622..ac05b3cfeacc 100644
--- a/include/linux/pinctrl/pinconf-generic.h
+++ b/include/linux/pinctrl/pinconf-generic.h
@@ -29,6 +29,11 @@
  *      if for example some other pin is going to drive the signal connected
  *      to it for a while. Pins used for input are usually always high
  *      impedance.
+ * @PIN_CONFIG_BIAS_BUS_HOLD: the pin will be set to weakly latch so that it
+ *      weakly drives the last value on a tristate bus, also known as a "bus
+ *      holder", "bus keeper" or "repeater". This allows another device on the
+ *      bus to change the value by driving the bus high or low and switching to
+ *      tristate. The argument is ignored.
  * @PIN_CONFIG_BIAS_PULL_UP: the pin will be pulled up (usually with high
  *      impedance to VDD). If the argument is != 0 pull-up is enabled,
  *      if it is 0, pull-up is disabled.
@@ -78,6 +83,7 @@
 enum pin_config_param {
         PIN_CONFIG_BIAS_DISABLE,
         PIN_CONFIG_BIAS_HIGH_IMPEDANCE,
+        PIN_CONFIG_BIAS_BUS_HOLD,
         PIN_CONFIG_BIAS_PULL_UP,
         PIN_CONFIG_BIAS_PULL_DOWN,
         PIN_CONFIG_DRIVE_PUSH_PULL,