Commit e0e1e39d authored by Linus Walleij's avatar Linus Walleij
Browse files

pinctrl: Add skew-delay pin config and bindings 



Some pin controllers (such as the Gemini) can control the
expected clock skew and output delay on certain pins with a
sub-nanosecond granularity. This is typically done by shunting
in a number of double inverters in front of or behind the pin.
Make it possible to configure this with a generic binding.

Cc: devicetree@vger.kernel.org
Acked-by: default avatarRob Herring <robh@kernel.org>
Acked-by: default avatarHans Ulli Kroll <ulli.kroll@googlemail.com>
Signed-off-by: default avatarLinus Walleij <linus.walleij@linaro.org>
parent 30ac0d3b

Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt

+4 −0
Original line number Diff line number Diff line
@@ -271,6 +271,10 @@ output-high - set the pin to output mode with high level 
sleep-hardware-state	- indicate this is sleep related state which will be programmed

			  into the registers for the sleep state.

slew-rate		- set the slew rate

skew-delay		- this affects the expected clock skew on input pins

			  and the delay before latching a value to an output

			  pin. Typically indicates how many double-inverters are

			  used to delay the signal.



For example:

drivers/pinctrl/pinconf-generic.c

+2 −0
Original line number Diff line number Diff line
@@ -49,6 +49,7 @@ static const struct pin_config_item conf_items[] = { 
	PCONFDUMP(PIN_CONFIG_POWER_SOURCE, "pin power source", "selector", true),

	PCONFDUMP(PIN_CONFIG_SLEEP_HARDWARE_STATE, "sleep hardware state", NULL, false),

	PCONFDUMP(PIN_CONFIG_SLEW_RATE, "slew rate", NULL, true),

	PCONFDUMP(PIN_CONFIG_SKEW_DELAY, "skew delay", NULL, true),

};



static void pinconf_generic_dump_one(struct pinctrl_dev *pctldev,
@@ -181,6 +182,7 @@ static const struct pinconf_generic_params dt_params[] = { 
	{ "power-source", PIN_CONFIG_POWER_SOURCE, 0 },

	{ "sleep-hardware-state", PIN_CONFIG_SLEEP_HARDWARE_STATE, 0 },

	{ "slew-rate", PIN_CONFIG_SLEW_RATE, 0 },

	{ "skew-delay", PIN_CONFIG_SKEW_DELAY, 0 },

};



/**

include/linux/pinctrl/pinconf-generic.h

+5 −0
Original line number Diff line number Diff line
@@ -90,6 +90,10 @@ 
 * @PIN_CONFIG_SLEW_RATE: if the pin can select slew rate, the argument to

 *	this parameter (on a custom format) tells the driver which alternative

 *	slew rate to use.

 * @PIN_CONFIG_SKEW_DELAY: if the pin has programmable skew rate (on inputs)

 *	or latch delay (on outputs) this parameter (in a custom format)

 *	specifies the clock skew or latch delay. It typically controls how

 *	many double inverters are put in front of the line.

 * @PIN_CONFIG_END: this is the last enumerator for pin configurations, if

 *	you need to pass in custom configurations to the pin controller, use

 *	PIN_CONFIG_END+1 as the base offset.
@@ -117,6 +121,7 @@ enum pin_config_param { 
	PIN_CONFIG_POWER_SOURCE,

	PIN_CONFIG_SLEEP_HARDWARE_STATE,

	PIN_CONFIG_SLEW_RATE,

	PIN_CONFIG_SKEW_DELAY,

	PIN_CONFIG_END = 0x7F,

	PIN_CONFIG_MAX = 0xFF,

};

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