| Message ID | 20171028133719.27528-2-linus.walleij@linaro.org |
|---|---|
| State | Accepted |
| Commit | e0e1e39de490a2d9b8a173363ccf2415ddada871 |
| Headers | show |
| Series | [1/4] pinctrl: gemini: Add missing functions | expand |
Hi Linus, On Sat, 28 Oct 2017, Linus Walleij wrote: > 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 > Signed-off-by: Linus Walleij <linus.walleij@linaro.org> > --- Acked-by: Hans Ulli Kroll <ulli.kroll@googlemail.com> -- To unsubscribe from this list: send the line "unsubscribe linux-gpio" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Thu, Nov 2, 2017 at 9:32 AM, Linus Walleij <linus.walleij@linaro.org> wrote: > On Wed, Nov 1, 2017 at 10:26 PM, Rob Herring <robh@kernel.org> wrote: >> On Sat, Oct 28, 2017 at 03:37:17PM +0200, Linus Walleij wrote: >>> 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 >>> Signed-off-by: Linus Walleij <linus.walleij@linaro.org> >>> --- >>> Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt | 4 ++++ >>> drivers/pinctrl/pinconf-generic.c | 2 ++ >>> include/linux/pinctrl/pinconf-generic.h | 5 +++++ >>> 3 files changed, 11 insertions(+) >>> >>> diff --git a/Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt b/Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt >>> index 4483cc31e531..ad9bbbba36e9 100644 >>> --- a/Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt >>> +++ b/Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt >>> @@ -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. >> >> Units? > > Number of double-inverters I guess, just as it says. > > skew-delay = <1>; // number of inverter pairs > > Like with other bindings of this type they are custom. > > The Gemini datasheet says "every unit represents about 0.2 ns". > > So if you set it to 1, that means (as far as I can guess) this > is shunted in: > > |\ |\ > --+ >o--+ >o--- > |/ |/ > > The signal will take ~0.2 ns to propagate through this. > For 2, there will be four inverters etc. > > It is dependent of production technology, and I do not know > if everyone is using something like double-inverters. > > We could try to define a value in picoseconds instead so I > would need to set this to 200 in that case if you think that is better: > > skew-delay = <200>; // picoseconds > > I think it would be kludgy since with increasing clock speeds > maybe picoseconds would be too big even. Nanoseconds is > apparently already a to coarse unit. Okay, it is fine. Acked-by: Rob Herring <robh@kernel.org> -- To unsubscribe from this list: send the line "unsubscribe linux-gpio" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt b/Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt index 4483cc31e531..ad9bbbba36e9 100644 --- a/Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt +++ b/Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt @@ -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: diff --git a/drivers/pinctrl/pinconf-generic.c b/drivers/pinctrl/pinconf-generic.c index 8eaa25c3384f..b4f7f8a458ea 100644 --- a/drivers/pinctrl/pinconf-generic.c +++ b/drivers/pinctrl/pinconf-generic.c @@ -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 }, }; /** diff --git a/include/linux/pinctrl/pinconf-generic.h b/include/linux/pinctrl/pinconf-generic.h index 5d8bc7f21c2a..ec6dadcc1fde 100644 --- a/include/linux/pinctrl/pinconf-generic.h +++ b/include/linux/pinctrl/pinconf-generic.h @@ -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, };
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 Signed-off-by: Linus Walleij <linus.walleij@linaro.org> --- Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt | 4 ++++ drivers/pinctrl/pinconf-generic.c | 2 ++ include/linux/pinctrl/pinconf-generic.h | 5 +++++ 3 files changed, 11 insertions(+) -- 2.13.6 -- To unsubscribe from this list: send the line "unsubscribe linux-gpio" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html