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pinconf-generic: add BIAS_BUS_HOLD pinconf

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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>
This commit is contained in:
James Hogan 2013-05-24 17:21:12 +01:00 committed by Linus Walleij
parent 73ae368cd3
commit a2df4269ca
2 changed files with 7 additions and 0 deletions
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1
drivers/pinctrl/pinconf-generic.c
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@ -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),

6
include/linux/pinctrl/pinconf-generic.h
View File

@ -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,