Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1561387 > unrolled thread

Re: [PATCH v7 3/8] PWM: add pwm-stm32 DT bindings

Back to article view | Back to linux.kernel

This discussion starts older than the indexed window; earlier articles aren't shown. The article labeled Started by below is the oldest one visible, not the original post.

Contents

  Re: [PATCH v7 3/8] PWM: add pwm-stm32 DT bindings Thierry Reding <thierry.reding@gmail.com> - 2017-01-18 10:40 +0100
    Re: [PATCH v7 3/8] PWM: add pwm-stm32 DT bindings Benjamin Gaignard <benjamin.gaignard@linaro.org> - 2017-01-18 10:50 +0100

#1561387 — Re: [PATCH v7 3/8] PWM: add pwm-stm32 DT bindings

[Multipart message — attachments visible in raw view] — view raw

On Thu, Jan 05, 2017 at 10:25:39AM +0100, Benjamin Gaignard wrote:
> Define bindings for pwm-stm32
> 
> version 6:
> - change st,breakinput parameter format to make it usuable on stm32f7 too.
> 
> version 2:
> - use parameters instead of compatible of handle the hardware configuration
> 
> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@st.com>
> ---
>  .../devicetree/bindings/pwm/pwm-stm32.txt          | 33 ++++++++++++++++++++++
>  1 file changed, 33 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/pwm/pwm-stm32.txt
> 
> diff --git a/Documentation/devicetree/bindings/pwm/pwm-stm32.txt b/Documentation/devicetree/bindings/pwm/pwm-stm32.txt
> new file mode 100644
> index 0000000..866f222
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/pwm/pwm-stm32.txt
> @@ -0,0 +1,33 @@
> +STMicroelectronics STM32 Timers PWM bindings
> +
> +Must be a sub-node of an STM32 Timers device tree node.
> +See ../mfd/stm32-timers.txt for details about the parent node.
> +
> +Required parameters:
> +- compatible:		Must be "st,stm32-pwm".
> +- pinctrl-names: 	Set to "default".
> +- pinctrl-0: 		List of phandles pointing to pin configuration nodes for PWM module.
> +			For Pinctrl properties see ../pinctrl/pinctrl-bindings.txt
> +
> +Optional parameters:
> +- st,breakinput:	Arrays of three u32 <index level filter> to describe break input configurations.
> +			"index" indicates on which break input the configuration should be applied.

It might be useful to specify what the valid values are for the break
input index.

Also, u32 is kind of a Linuxism, perhaps "Arrays of three cells"? Also,
does this mean there can be multiple entries? Such as 6 cells for two
configurations? What's the maximum number of such configurations?

If it's possible to specify multiple configurations, maybe a slightly
clearer wording would be: "One or more <index level filter> triplets to
describe..."

> +			"level" gives the active level (0=low or 1=high) for this configuration.

So how does this work exactly? "level" specifies the output level if the
filter value is matched?

> +			"filter" gives the filtering value to be applied.

Is this a single value at which "level" will be applied? Or is it an
upper/lower bound that can be used to restrict the output to "level" if
the signal goes beyond/below a certain threshold?

Maybe an example would clarify this. Or perhaps a reference to a manual
where a more in-depth description of this functionality can be found.

Thierry

[toc] | [next] | [standalone]

#1561412

2017-01-18 10:20 GMT+01:00 Thierry Reding <thierry.reding@gmail.com>:
> On Thu, Jan 05, 2017 at 10:25:39AM +0100, Benjamin Gaignard wrote:
>> Define bindings for pwm-stm32
>>
>> version 6:
>> - change st,breakinput parameter format to make it usuable on stm32f7 too.
>>
>> version 2:
>> - use parameters instead of compatible of handle the hardware configuration
>>
>> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@st.com>
>> ---
>>  .../devicetree/bindings/pwm/pwm-stm32.txt          | 33 ++++++++++++++++++++++
>>  1 file changed, 33 insertions(+)
>>  create mode 100644 Documentation/devicetree/bindings/pwm/pwm-stm32.txt
>>
>> diff --git a/Documentation/devicetree/bindings/pwm/pwm-stm32.txt b/Documentation/devicetree/bindings/pwm/pwm-stm32.txt
>> new file mode 100644
>> index 0000000..866f222
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/pwm/pwm-stm32.txt
>> @@ -0,0 +1,33 @@
>> +STMicroelectronics STM32 Timers PWM bindings
>> +
>> +Must be a sub-node of an STM32 Timers device tree node.
>> +See ../mfd/stm32-timers.txt for details about the parent node.
>> +
>> +Required parameters:
>> +- compatible:                Must be "st,stm32-pwm".
>> +- pinctrl-names:     Set to "default".
>> +- pinctrl-0:                 List of phandles pointing to pin configuration nodes for PWM module.
>> +                     For Pinctrl properties see ../pinctrl/pinctrl-bindings.txt
>> +
>> +Optional parameters:
>> +- st,breakinput:     Arrays of three u32 <index level filter> to describe break input configurations.
>> +                     "index" indicates on which break input the configuration should be applied.
>
> It might be useful to specify what the valid values are for the break
> input index.

It could 0 and 1, I will add this information.

>
> Also, u32 is kind of a Linuxism, perhaps "Arrays of three cells"? Also,
> does this mean there can be multiple entries? Such as 6 cells for two
> configurations? What's the maximum number of such configurations?
>
> If it's possible to specify multiple configurations, maybe a slightly
> clearer wording would be: "One or more <index level filter> triplets to
> describe..."
>

You can have one configuration per index so I will rephrase it like that:
One or two <index level filter> to describe break input configurations.
"index" indicates on which break input (0 or 1 ) the configuration
should be applied.


>> +                     "level" gives the active level (0=low or 1=high) for this configuration.
>
> So how does this work exactly? "level" specifies the output level if the
> filter value is matched?

No it specify on which input level the break event is generated

>
>> +                     "filter" gives the filtering value to be applied.
>
> Is this a single value at which "level" will be applied? Or is it an
> upper/lower bound that can be used to restrict the output to "level" if
> the signal goes beyond/below a certain threshold?

Very very basically filter is more a debounce value set on the signal
to avoid glitches.
The goal of break input feature is to stop PWM generation in hardware
errors failure case.

For a more completed description you can read "using break input
function" (starting page 645) in this doc:

http://www.st.com/content/ccc/resource/technical/document/reference_manual/c5/cf/ef/52/c0/f1/4b/fa/DM00124865.pdf/files/DM00124865.pdf/jcr:content/translations/en.DM00124865.pdf

>
> Maybe an example would clarify this. Or perhaps a reference to a manual
> where a more in-depth description of this functionality can be found.
>
> Thierry



-- 
Benjamin Gaignard

Graphic Study Group

Linaro.org │ Open source software for ARM SoCs

Follow Linaro: Facebook | Twitter | Blog

[toc] | [prev] | [standalone]

Back to top | Article view | linux.kernel

csiph-web