From: Linus Walleij <[email protected]>
It is counter-intuitive to have "0" mean disable in a boolean
manner for electronic properties of pins such as pull-up and
pull-down. Therefore, define that a pull-up/pull-down argument
of 0 to such a generic option means that the pin is
short-circuited to VDD or GROUND. Pull disablement shall be
done using PIN_CONFIG_BIAS_DISABLE.
Cc: Heiko St?bner <[email protected]>
Cc: James Hogan <[email protected]>
Cc: Laurent Pinchart <[email protected]>
Signed-off-by: Linus Walleij <[email protected]>
---
include/linux/pinctrl/pinconf-generic.h | 13 +++++++------
1 file changed, 7 insertions(+), 6 deletions(-)
diff --git a/include/linux/pinctrl/pinconf-generic.h b/include/linux/pinctrl/pinconf-generic.h
index d414a77..67780f5 100644
--- a/include/linux/pinctrl/pinconf-generic.h
+++ b/include/linux/pinctrl/pinconf-generic.h
@@ -36,14 +36,15 @@
* 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.
+ * if it is 0, pull-up it total, i.e. the pin is connected to VDD.
* @PIN_CONFIG_BIAS_PULL_DOWN: the pin will be pulled down (usually with high
* impedance to GROUND). If the argument is != 0 pull-down is enabled,
- * if it is 0, pull-down is disabled.
+ * if it is 0, pull-down is total, i.e. the pin is connected to GROUND.
* @PIN_CONFIG_BIAS_PULL_PIN_DEFAULT: the pin will be pulled up or down based
* on embedded knowledge of the controller, like current mux function.
- * If the argument is != 0 pull up/down is enabled, if it is 0,
- * the pull is disabled.
+ * If the argument is != 0 pull up/down is enabled, if it is 0, the
+ * configuration is ignored. The proper way to disable it is to use
+ * @PIN_CONFIG_BIAS_DISABLE.
* @PIN_CONFIG_DRIVE_PUSH_PULL: the pin will be driven actively high and
* low, this is the most typical case and is typically achieved with two
* active transistors on the output. Setting this config will enable
@@ -72,8 +73,8 @@
* supplies, the argument to this parameter (on a custom format) tells
* the driver which alternative power source to use.
* @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.
+ * this parameter (on a custom format) tells the driver which alternative
+ * slew rate to use.
* @PIN_CONFIG_LOW_POWER_MODE: this will configure the pin for low power
* operation, if several modes of operation are supported these can be
* passed in the argument on a custom form, else just use argument 1
--
1.7.11.3
Am Sonntag, 16. Juni 2013, 12:45:48 schrieb Linus Walleij:
> From: Linus Walleij <[email protected]>
>
> It is counter-intuitive to have "0" mean disable in a boolean
> manner for electronic properties of pins such as pull-up and
> pull-down. Therefore, define that a pull-up/pull-down argument
> of 0 to such a generic option means that the pin is
> short-circuited to VDD or GROUND. Pull disablement shall be
> done using PIN_CONFIG_BIAS_DISABLE.
>
> Cc: Heiko St�bner <[email protected]>
> Cc: James Hogan <[email protected]>
> Cc: Laurent Pinchart <[email protected]>
> Signed-off-by: Linus Walleij <[email protected]>
very nice :-)
Acked-by: Heiko Stuebner <[email protected]>
> ---
> include/linux/pinctrl/pinconf-generic.h | 13 +++++++------
> 1 file changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/include/linux/pinctrl/pinconf-generic.h
> b/include/linux/pinctrl/pinconf-generic.h index d414a77..67780f5 100644
> --- a/include/linux/pinctrl/pinconf-generic.h
> +++ b/include/linux/pinctrl/pinconf-generic.h
> @@ -36,14 +36,15 @@
> * 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.
> + * if it is 0, pull-up it total, i.e. the pin is connected to VDD.
> * @PIN_CONFIG_BIAS_PULL_DOWN: the pin will be pulled down (usually with
> high * impedance to GROUND). If the argument is != 0 pull-down is enabled,
> - * if it is 0, pull-down is disabled.
> + * if it is 0, pull-down is total, i.e. the pin is connected to GROUND.
> * @PIN_CONFIG_BIAS_PULL_PIN_DEFAULT: the pin will be pulled up or down
> based * on embedded knowledge of the controller, like current mux
> function. - * If the argument is != 0 pull up/down is enabled, if it is 0,
> - * the pull is disabled.
> + * If the argument is != 0 pull up/down is enabled, if it is 0, the
> + * configuration is ignored. The proper way to disable it is to use
> + * @PIN_CONFIG_BIAS_DISABLE.
> * @PIN_CONFIG_DRIVE_PUSH_PULL: the pin will be driven actively high and
> * low, this is the most typical case and is typically achieved with two
> * active transistors on the output. Setting this config will enable
> @@ -72,8 +73,8 @@
> * supplies, the argument to this parameter (on a custom format) tells
> * the driver which alternative power source to use.
> * @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.
> + * this parameter (on a custom format) tells the driver which
alternative
> + * slew rate to use.
> * @PIN_CONFIG_LOW_POWER_MODE: this will configure the pin for low power
> * operation, if several modes of operation are supported these can be
> * passed in the argument on a custom form, else just use argument 1
Hi Linus,
On Sunday 16 June 2013 12:45:48 Linus Walleij wrote:
> From: Linus Walleij <[email protected]>
>
> It is counter-intuitive to have "0" mean disable in a boolean
> manner for electronic properties of pins such as pull-up and
> pull-down. Therefore, define that a pull-up/pull-down argument
> of 0 to such a generic option means that the pin is
> short-circuited to VDD or GROUND. Pull disablement shall be
> done using PIN_CONFIG_BIAS_DISABLE.
>
> Cc: Heiko St�bner <[email protected]>
> Cc: James Hogan <[email protected]>
> Cc: Laurent Pinchart <[email protected]>
> Signed-off-by: Linus Walleij <[email protected]>
Nice clarification, thank you.
Acked-by: Laurent Pinchart <[email protected]>
(with one small comment below)
> ---
> include/linux/pinctrl/pinconf-generic.h | 13 +++++++------
> 1 file changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/include/linux/pinctrl/pinconf-generic.h
> b/include/linux/pinctrl/pinconf-generic.h index d414a77..67780f5 100644
> --- a/include/linux/pinctrl/pinconf-generic.h
> +++ b/include/linux/pinctrl/pinconf-generic.h
> @@ -36,14 +36,15 @@
> * 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.
> + * if it is 0, pull-up it total, i.e. the pin is connected to VDD.
> * @PIN_CONFIG_BIAS_PULL_DOWN: the pin will be pulled down (usually with
> high * impedance to GROUND). If the argument is != 0 pull-down is enabled,
> - * if it is 0, pull-down is disabled.
> + * if it is 0, pull-down is total, i.e. the pin is connected to GROUND.
> * @PIN_CONFIG_BIAS_PULL_PIN_DEFAULT: the pin will be pulled up or down
> based * on embedded knowledge of the controller, like current mux function.
> - * If the argument is != 0 pull up/down is enabled, if it is 0,
> - * the pull is disabled.
> + * If the argument is != 0 pull up/down is enabled, if it is 0, the
> + * configuration is ignored. The proper way to disable it is to use
> + * @PIN_CONFIG_BIAS_DISABLE.
> * @PIN_CONFIG_DRIVE_PUSH_PULL: the pin will be driven actively high and
> * low, this is the most typical case and is typically achieved with two
> * active transistors on the output. Setting this config will enable
> @@ -72,8 +73,8 @@
> * supplies, the argument to this parameter (on a custom format) tells
> * the driver which alternative power source to use.
> * @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.
> + * this parameter (on a custom format) tells the driver which
alternative
> + * slew rate to use.
This hunk doesn't seem to belong to the patch.
> * @PIN_CONFIG_LOW_POWER_MODE: this will configure the pin for low power
> * operation, if several modes of operation are supported these can be
> * passed in the argument on a custom form, else just use argument 1
--
Regards,
Laurent Pinchart
On 16/06/13 22:45, Linus Walleij wrote:
> From: Linus Walleij <[email protected]>
>
> It is counter-intuitive to have "0" mean disable in a boolean
> manner for electronic properties of pins such as pull-up and
> pull-down. Therefore, define that a pull-up/pull-down argument
> of 0 to such a generic option means that the pin is
> short-circuited to VDD or GROUND. Pull disablement shall be
> done using PIN_CONFIG_BIAS_DISABLE.
>
> Cc: Heiko St�bner <[email protected]>
> Cc: James Hogan <[email protected]>
> Cc: Laurent Pinchart <[email protected]>
> Signed-off-by: Linus Walleij <[email protected]>
> ---
> include/linux/pinctrl/pinconf-generic.h | 13 +++++++------
> 1 file changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/include/linux/pinctrl/pinconf-generic.h b/include/linux/pinctrl/pinconf-generic.h
> index d414a77..67780f5 100644
> --- a/include/linux/pinctrl/pinconf-generic.h
> +++ b/include/linux/pinctrl/pinconf-generic.h
> @@ -36,14 +36,15 @@
> * 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.
> + * if it is 0, pull-up it total, i.e. the pin is connected to VDD.
s/it/is
> * @PIN_CONFIG_BIAS_PULL_DOWN: the pin will be pulled down (usually with high
> * impedance to GROUND). If the argument is != 0 pull-down is enabled,
> - * if it is 0, pull-down is disabled.
> + * if it is 0, pull-down is total, i.e. the pin is connected to GROUND.
> * @PIN_CONFIG_BIAS_PULL_PIN_DEFAULT: the pin will be pulled up or down based
> * on embedded knowledge of the controller, like current mux function.
> - * If the argument is != 0 pull up/down is enabled, if it is 0,
> - * the pull is disabled.
> + * If the argument is != 0 pull up/down is enabled, if it is 0, the
> + * configuration is ignored. The proper way to disable it is to use
> + * @PIN_CONFIG_BIAS_DISABLE.
> * @PIN_CONFIG_DRIVE_PUSH_PULL: the pin will be driven actively high and
> * low, this is the most typical case and is typically achieved with two
> * active transistors on the output. Setting this config will enable
> @@ -72,8 +73,8 @@
> * supplies, the argument to this parameter (on a custom format) tells
> * the driver which alternative power source to use.
> * @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.
> + * this parameter (on a custom format) tells the driver which alternative
> + * slew rate to use.
> * @PIN_CONFIG_LOW_POWER_MODE: this will configure the pin for low power
> * operation, if several modes of operation are supported these can be
> * passed in the argument on a custom form, else just use argument 1
>
>
> _______________________________________________
> linux-arm-kernel mailing list
> [email protected]
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
On Mon, Jun 17, 2013 at 7:57 AM, Lothar Wa?mann <[email protected]> wrote:
> Linus Walleij writes:
>> - * if it is 0, pull-up is disabled.
>> + * if it is 0, pull-up it total, i.e. the pin is connected to VDD.
> ^^
> 'is'?
Thanks for noticing, fixed this up when applying.
Yours,
Linus Walleij
On 06/16/2013 04:45 AM, Linus Walleij wrote:
> From: Linus Walleij <[email protected]>
>
> It is counter-intuitive to have "0" mean disable in a boolean
> manner for electronic properties of pins such as pull-up and
> pull-down. Therefore, define that a pull-up/pull-down argument
> of 0 to such a generic option means that the pin is
> short-circuited to VDD or GROUND. Pull disablement shall be
> done using PIN_CONFIG_BIAS_DISABLE.
>
> Cc: Heiko St�bner <[email protected]>
> Cc: James Hogan <[email protected]>
> Cc: Laurent Pinchart <[email protected]>
> Signed-off-by: Linus Walleij <[email protected]>
> ---
> include/linux/pinctrl/pinconf-generic.h | 13 +++++++------
> 1 file changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/include/linux/pinctrl/pinconf-generic.h b/include/linux/pinctrl/pinconf-generic.h
> index d414a77..67780f5 100644
> --- a/include/linux/pinctrl/pinconf-generic.h
> +++ b/include/linux/pinctrl/pinconf-generic.h
> @@ -36,14 +36,15 @@
> * 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.
> + * if it is 0, pull-up it total, i.e. the pin is connected to VDD.
> * @PIN_CONFIG_BIAS_PULL_DOWN: the pin will be pulled down (usually with high
> * impedance to GROUND). If the argument is != 0 pull-down is enabled,
> - * if it is 0, pull-down is disabled.
> + * if it is 0, pull-down is total, i.e. the pin is connected to GROUND.
> * @PIN_CONFIG_BIAS_PULL_PIN_DEFAULT: the pin will be pulled up or down based
> * on embedded knowledge of the controller, like current mux function.
> - * If the argument is != 0 pull up/down is enabled, if it is 0,
> - * the pull is disabled.
> + * If the argument is != 0 pull up/down is enabled, if it is 0, the
> + * configuration is ignored. The proper way to disable it is to use
> + * @PIN_CONFIG_BIAS_DISABLE.
Why treat PULL_UP/PULL_DOWN differently from PULL_PIN_DEFAULT?
PULL_PIN_DEFAULT is logically simply a macro that selects PULL_UP/DOWN
based on what's "normal" for the pin's expected usage, so surely the
value associated with that option should behave identically?
On 19/06/13 23:03, Stephen Warren wrote:
> On 06/16/2013 04:45 AM, Linus Walleij wrote:
>> From: Linus Walleij <[email protected]>
>>
>> It is counter-intuitive to have "0" mean disable in a boolean
>> manner for electronic properties of pins such as pull-up and
>> pull-down. Therefore, define that a pull-up/pull-down argument
>> of 0 to such a generic option means that the pin is
>> short-circuited to VDD or GROUND. Pull disablement shall be
>> done using PIN_CONFIG_BIAS_DISABLE.
>>
>> Cc: Heiko St�bner <[email protected]>
>> Cc: James Hogan <[email protected]>
>> Cc: Laurent Pinchart <[email protected]>
>> Signed-off-by: Linus Walleij <[email protected]>
>> ---
>> include/linux/pinctrl/pinconf-generic.h | 13 +++++++------
>> 1 file changed, 7 insertions(+), 6 deletions(-)
>>
>> diff --git a/include/linux/pinctrl/pinconf-generic.h b/include/linux/pinctrl/pinconf-generic.h
>> index d414a77..67780f5 100644
>> --- a/include/linux/pinctrl/pinconf-generic.h
>> +++ b/include/linux/pinctrl/pinconf-generic.h
>> @@ -36,14 +36,15 @@
>> * 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.
>> + * if it is 0, pull-up it total, i.e. the pin is connected to VDD.
>> * @PIN_CONFIG_BIAS_PULL_DOWN: the pin will be pulled down (usually with high
>> * impedance to GROUND). If the argument is != 0 pull-down is enabled,
>> - * if it is 0, pull-down is disabled.
>> + * if it is 0, pull-down is total, i.e. the pin is connected to GROUND.
>> * @PIN_CONFIG_BIAS_PULL_PIN_DEFAULT: the pin will be pulled up or down based
>> * on embedded knowledge of the controller, like current mux function.
>> - * If the argument is != 0 pull up/down is enabled, if it is 0,
>> - * the pull is disabled.
>> + * If the argument is != 0 pull up/down is enabled, if it is 0, the
>> + * configuration is ignored. The proper way to disable it is to use
>> + * @PIN_CONFIG_BIAS_DISABLE.
>
> Why treat PULL_UP/PULL_DOWN differently from PULL_PIN_DEFAULT?
> PULL_PIN_DEFAULT is logically simply a macro that selects PULL_UP/DOWN
> based on what's "normal" for the pin's expected usage, so surely the
> value associated with that option should behave identically?
I'm not familiar with hardware that does this so I could be way wrong
here, but presumably if there's a default up/down, there's probably a
default resistance too. Does it really make sense to say
"pull up or down depending on whatever the pin is intended for... but
whichever it is must be XXX Ohm"?
If you know the resistance you want, you surely already know whether you
want it pull up or down with that resistence.
Cheers
James
On 06/20/2013 06:38 AM, James Hogan wrote:
> On 19/06/13 23:03, Stephen Warren wrote:
>> On 06/16/2013 04:45 AM, Linus Walleij wrote:
>>> From: Linus Walleij <[email protected]>
>>>
>>> It is counter-intuitive to have "0" mean disable in a boolean
>>> manner for electronic properties of pins such as pull-up and
>>> pull-down. Therefore, define that a pull-up/pull-down argument
>>> of 0 to such a generic option means that the pin is
>>> short-circuited to VDD or GROUND. Pull disablement shall be
>>> done using PIN_CONFIG_BIAS_DISABLE.
>>>
>>> Cc: Heiko St�bner <[email protected]>
>>> Cc: James Hogan <[email protected]>
>>> Cc: Laurent Pinchart <[email protected]>
>>> Signed-off-by: Linus Walleij <[email protected]>
>>> ---
>>> include/linux/pinctrl/pinconf-generic.h | 13 +++++++------
>>> 1 file changed, 7 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/include/linux/pinctrl/pinconf-generic.h b/include/linux/pinctrl/pinconf-generic.h
>>> index d414a77..67780f5 100644
>>> --- a/include/linux/pinctrl/pinconf-generic.h
>>> +++ b/include/linux/pinctrl/pinconf-generic.h
>>> @@ -36,14 +36,15 @@
>>> * 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.
>>> + * if it is 0, pull-up it total, i.e. the pin is connected to VDD.
>>> * @PIN_CONFIG_BIAS_PULL_DOWN: the pin will be pulled down (usually with high
>>> * impedance to GROUND). If the argument is != 0 pull-down is enabled,
>>> - * if it is 0, pull-down is disabled.
>>> + * if it is 0, pull-down is total, i.e. the pin is connected to GROUND.
>>> * @PIN_CONFIG_BIAS_PULL_PIN_DEFAULT: the pin will be pulled up or down based
>>> * on embedded knowledge of the controller, like current mux function.
>>> - * If the argument is != 0 pull up/down is enabled, if it is 0,
>>> - * the pull is disabled.
>>> + * If the argument is != 0 pull up/down is enabled, if it is 0, the
>>> + * configuration is ignored. The proper way to disable it is to use
>>> + * @PIN_CONFIG_BIAS_DISABLE.
>>
>> Why treat PULL_UP/PULL_DOWN differently from PULL_PIN_DEFAULT?
>> PULL_PIN_DEFAULT is logically simply a macro that selects PULL_UP/DOWN
>> based on what's "normal" for the pin's expected usage, so surely the
>> value associated with that option should behave identically?
>
> I'm not familiar with hardware that does this so I could be way wrong
> here, but presumably if there's a default up/down, there's probably a
> default resistance too. Does it really make sense to say
> "pull up or down depending on whatever the pin is intended for... but
> whichever it is must be XXX Ohm"?
> If you know the resistance you want, you surely already know whether you
> want it pull up or down with that resistence.
IIRC the idea of the PULL_PIN_DEFAULT was to avoid having to specify
UP/DOWN for each pin/group, but could just say "default", which would
then reduce the number of pinctrl mapping table entries or pinctrl DT
property entries. I don't think this would have any interaction with
setting the resistance; it's entirely plausible that you'd want the same
explicit, or same default, resistance, for all pins, irrespective of
pull-up vs. down.
Hi Stephen,
On Friday 21 June 2013 13:06:47 Stephen Warren wrote:
> On 06/20/2013 06:38 AM, James Hogan wrote:
> > On 19/06/13 23:03, Stephen Warren wrote:
> >> On 06/16/2013 04:45 AM, Linus Walleij wrote:
> >>> From: Linus Walleij <[email protected]>
> >>>
> >>> It is counter-intuitive to have "0" mean disable in a boolean
> >>> manner for electronic properties of pins such as pull-up and
> >>> pull-down. Therefore, define that a pull-up/pull-down argument
> >>> of 0 to such a generic option means that the pin is
> >>> short-circuited to VDD or GROUND. Pull disablement shall be
> >>> done using PIN_CONFIG_BIAS_DISABLE.
> >>>
> >>> Cc: Heiko St�bner <[email protected]>
> >>> Cc: James Hogan <[email protected]>
> >>> Cc: Laurent Pinchart <[email protected]>
> >>> Signed-off-by: Linus Walleij <[email protected]>
> >>> ---
> >>>
> >>> include/linux/pinctrl/pinconf-generic.h | 13 +++++++------
> >>> 1 file changed, 7 insertions(+), 6 deletions(-)
> >>>
> >>> diff --git a/include/linux/pinctrl/pinconf-generic.h
> >>> b/include/linux/pinctrl/pinconf-generic.h index d414a77..67780f5 100644
> >>> --- a/include/linux/pinctrl/pinconf-generic.h
> >>> +++ b/include/linux/pinctrl/pinconf-generic.h
> >>> @@ -36,14 +36,15 @@
> >>>
> >>> * 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.
> >>> + * if it is 0, pull-up it total, i.e. the pin is connected to VDD.
> >>>
> >>> * @PIN_CONFIG_BIAS_PULL_DOWN: the pin will be pulled down (usually
> >>> with high * impedance to GROUND). If the argument is != 0 pull-down
> >>> is enabled,>>>
> >>> - * if it is 0, pull-down is disabled.
> >>> + * if it is 0, pull-down is total, i.e. the pin is connected to GROUND.
> >>>
> >>> * @PIN_CONFIG_BIAS_PULL_PIN_DEFAULT: the pin will be pulled up or down
> >>> based * on embedded knowledge of the controller, like current mux
> >>> function.>>>
> >>> - * If the argument is != 0 pull up/down is enabled, if it is 0,
> >>> - * the pull is disabled.
> >>> + * If the argument is != 0 pull up/down is enabled, if it is 0, the
> >>> + * configuration is ignored. The proper way to disable it is to use
> >>> + * @PIN_CONFIG_BIAS_DISABLE.
> >>
> >> Why treat PULL_UP/PULL_DOWN differently from PULL_PIN_DEFAULT?
> >> PULL_PIN_DEFAULT is logically simply a macro that selects PULL_UP/DOWN
> >> based on what's "normal" for the pin's expected usage, so surely the
> >> value associated with that option should behave identically?
> >
> > I'm not familiar with hardware that does this so I could be way wrong
> > here, but presumably if there's a default up/down, there's probably a
> > default resistance too. Does it really make sense to say
> > "pull up or down depending on whatever the pin is intended for... but
> > whichever it is must be XXX Ohm"?
> > If you know the resistance you want, you surely already know whether you
> > want it pull up or down with that resistence.
>
> IIRC the idea of the PULL_PIN_DEFAULT was to avoid having to specify
> UP/DOWN for each pin/group, but could just say "default", which would
> then reduce the number of pinctrl mapping table entries or pinctrl DT
> property entries.
I may be mistaken, but I've understood the PULL_PIN_DEFAULT option as a way to
select the default bias configuration when the default value is hardware-
controlled, not as a pure software option.
> I don't think this would have any interaction with setting the resistance;
> it's entirely plausible that you'd want the same explicit, or same default,
> resistance, for all pins, irrespective of pull-up vs. down.
--
Regards,
Laurent Pinchart
Am Samstag, 22. Juni 2013, 01:30:18 schrieb Laurent Pinchart:
> Hi Stephen,
>
> On Friday 21 June 2013 13:06:47 Stephen Warren wrote:
> > On 06/20/2013 06:38 AM, James Hogan wrote:
> > > On 19/06/13 23:03, Stephen Warren wrote:
> > >> On 06/16/2013 04:45 AM, Linus Walleij wrote:
> > >>> From: Linus Walleij <[email protected]>
> > >>>
> > >>> It is counter-intuitive to have "0" mean disable in a boolean
> > >>> manner for electronic properties of pins such as pull-up and
> > >>> pull-down. Therefore, define that a pull-up/pull-down argument
> > >>> of 0 to such a generic option means that the pin is
> > >>> short-circuited to VDD or GROUND. Pull disablement shall be
> > >>> done using PIN_CONFIG_BIAS_DISABLE.
> > >>>
> > >>> Cc: Heiko St�bner <[email protected]>
> > >>> Cc: James Hogan <[email protected]>
> > >>> Cc: Laurent Pinchart <[email protected]>
> > >>> Signed-off-by: Linus Walleij <[email protected]>
> > >>> ---
> > >>>
> > >>> include/linux/pinctrl/pinconf-generic.h | 13 +++++++------
> > >>> 1 file changed, 7 insertions(+), 6 deletions(-)
> > >>>
> > >>> diff --git a/include/linux/pinctrl/pinconf-generic.h
> > >>> b/include/linux/pinctrl/pinconf-generic.h index d414a77..67780f5
> > >>> 100644 --- a/include/linux/pinctrl/pinconf-generic.h
> > >>> +++ b/include/linux/pinctrl/pinconf-generic.h
> > >>> @@ -36,14 +36,15 @@
> > >>>
> > >>> * 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.
> > >>> + * if it is 0, pull-up it total, i.e. the pin is connected to VDD.
> > >>>
> > >>> * @PIN_CONFIG_BIAS_PULL_DOWN: the pin will be pulled down (usually
> > >>> with high * impedance to GROUND). If the argument is != 0 pull-down
> > >>> is enabled,>>>
> > >>>
> > >>> - * if it is 0, pull-down is disabled.
> > >>> + * if it is 0, pull-down is total, i.e. the pin is connected to
> > >>> GROUND.
> > >>>
> > >>> * @PIN_CONFIG_BIAS_PULL_PIN_DEFAULT: the pin will be pulled up or
> > >>> down based * on embedded knowledge of the controller, like current
> > >>> mux function.>>>
> > >>>
> > >>> - * If the argument is != 0 pull up/down is enabled, if it is 0,
> > >>> - * the pull is disabled.
> > >>> + * If the argument is != 0 pull up/down is enabled, if it is 0, the
> > >>> + * configuration is ignored. The proper way to disable it is to use
> > >>> + * @PIN_CONFIG_BIAS_DISABLE.
> > >>
> > >> Why treat PULL_UP/PULL_DOWN differently from PULL_PIN_DEFAULT?
> > >> PULL_PIN_DEFAULT is logically simply a macro that selects PULL_UP/DOWN
> > >> based on what's "normal" for the pin's expected usage, so surely the
> > >> value associated with that option should behave identically?
> > >
> > > I'm not familiar with hardware that does this so I could be way wrong
> > > here, but presumably if there's a default up/down, there's probably a
> > > default resistance too. Does it really make sense to say
> > > "pull up or down depending on whatever the pin is intended for... but
> > > whichever it is must be XXX Ohm"?
> > > If you know the resistance you want, you surely already know whether
> > > you want it pull up or down with that resistence.
> >
> > IIRC the idea of the PULL_PIN_DEFAULT was to avoid having to specify
> > UP/DOWN for each pin/group, but could just say "default", which would
> > then reduce the number of pinctrl mapping table entries or pinctrl DT
> > property entries.
>
> I may be mistaken, but I've understood the PULL_PIN_DEFAULT option as a way
> to select the default bias configuration when the default value is
> hardware- controlled, not as a pure software option.
Yep that was the original intent ... to handle hardware that hides the
complete logic from the software and you only get to turn it on or off, while
the direction and other params are determined internally for example by the
pin function.
>
> > I don't think this would have any interaction with setting the
> > resistance; it's entirely plausible that you'd want the same explicit,
> > or same default, resistance, for all pins, irrespective of pull-up vs.
> > down.
On Sat, Jun 22, 2013 at 1:39 AM, Heiko St?bner <[email protected]> wrote:
> Am Samstag, 22. Juni 2013, 01:30:18 schrieb Laurent Pinchart:
>> [Stephen]
>> > IIRC the idea of the PULL_PIN_DEFAULT was to avoid having to specify
>> > UP/DOWN for each pin/group, but could just say "default", which would
>> > then reduce the number of pinctrl mapping table entries or pinctrl DT
>> > property entries.
>>
>> I may be mistaken, but I've understood the PULL_PIN_DEFAULT option as a way
>> to select the default bias configuration when the default value is
>> hardware- controlled, not as a pure software option.
>
> Yep that was the original intent ... to handle hardware that hides the
> complete logic from the software and you only get to turn it on or off, while
> the direction and other params are determined internally for example by the
> pin function.
Heiko, can you send a documentation patch to clarify this so we
don't get any misunderstandings?
Maybe it'd be useful for software purposes as well, but let's save
that for when it gets used like that.
Yours,
Linus Walleij
Am Montag, 24. Juni 2013, 14:24:12 schrieb Linus Walleij:
> On Sat, Jun 22, 2013 at 1:39 AM, Heiko St?bner <[email protected]> wrote:
> > Am Samstag, 22. Juni 2013, 01:30:18 schrieb Laurent Pinchart:
> >> [Stephen]
> >>
> >> > IIRC the idea of the PULL_PIN_DEFAULT was to avoid having to specify
> >> > UP/DOWN for each pin/group, but could just say "default", which would
> >> > then reduce the number of pinctrl mapping table entries or pinctrl DT
> >> > property entries.
> >>
> >> I may be mistaken, but I've understood the PULL_PIN_DEFAULT option as a
> >> way to select the default bias configuration when the default value is
> >> hardware- controlled, not as a pure software option.
> >
> > Yep that was the original intent ... to handle hardware that hides the
> > complete logic from the software and you only get to turn it on or off,
> > while the direction and other params are determined internally for
> > example by the pin function.
>
> Heiko, can you send a documentation patch to clarify this so we
> don't get any misunderstandings?
>
> Maybe it'd be useful for software purposes as well, but let's save
> that for when it gets used like that.
will try to get this (and the changes from the other mail) done today
Heiko
On 06/21/2013 05:30 PM, Laurent Pinchart wrote:
> Hi Stephen,
>
> On Friday 21 June 2013 13:06:47 Stephen Warren wrote:
...
>> IIRC the idea of the PULL_PIN_DEFAULT was to avoid having to specify
>> UP/DOWN for each pin/group, but could just say "default", which would
>> then reduce the number of pinctrl mapping table entries or pinctrl DT
>> property entries.
>
> I may be mistaken, but I've understood the PULL_PIN_DEFAULT option as a way to
> select the default bias configuration when the default value is hardware-
> controlled, not as a pure software option.
That's my understanding too.