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>

diff --git a/drivers/pinctrl/pinconf-generic.c b/drivers/pinctrl/pinconf-generic.c
index 33a5392cf40ca0da06acdf73b9c8c12f13f2c10f..ba465b3e85eff03c13b54ad5f4582678903338b1 100644 (file)
--- a/drivers/pinctrl/pinconf-generic.c
+++ b/drivers/pinctrl/pinconf-generic.c
@@ -37,6 +37,7 @@ struct pin_config_item {
 static struct pin_config_item conf_items[] = {
        PCONFDUMP(PIN_CONFIG_BIAS_DISABLE, "input bias disabled", NULL),
        PCONFDUMP(PIN_CONFIG_BIAS_HIGH_IMPEDANCE, "input bias high impedance", NULL),
+       PCONFDUMP(PIN_CONFIG_BIAS_BUS_HOLD, "input bias bus hold", NULL),
        PCONFDUMP(PIN_CONFIG_BIAS_PULL_UP, "input bias pull up", NULL),
        PCONFDUMP(PIN_CONFIG_BIAS_PULL_DOWN, "input bias pull down", NULL),
        PCONFDUMP(PIN_CONFIG_DRIVE_PUSH_PULL, "output drive push pull", NULL),

diff --git a/include/linux/pinctrl/pinconf-generic.h b/include/linux/pinctrl/pinconf-generic.h
index 6aa238096622441de2125f3a7658fe2777f349a1..ac05b3cfeacc0c0ae7ca4f708385ae01d070616d 100644 (file)
--- 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,