[PATCH 2/2] DT: pwm: Add NXP LPC18xx PWM/SCT binding documentation

[Ezequiel Garcia]

+devicetree guys

On 28 July 2015 at 20:22, Joachim  Eastwood <manabian at gmail.com> wrote:
> On 29 July 2015 at 00:45, Ezequiel Garcia <ezequiel at vanguardiasur.com.ar> wrote:
>> On 28 July 2015 at 19:37, Joachim  Eastwood <manabian at gmail.com> wrote:
>>> On 27 July 2015 at 06:45, Ariel D'Alessandro <ariel at vanguardiasur.com.ar> wrote:
>>>> Add the devicetree binding document for NXP LPC18xx PWM/SCT.
>>>>
>>>> Signed-off-by: Ariel D'Alessandro <ariel at vanguardiasur.com.ar>
>>>> ---
>>>>  .../devicetree/bindings/pwm/lpc1850-pwm.txt          | 20 ++++++++++++++++++++
>>>>  1 file changed, 20 insertions(+)
>>>>  create mode 100644 Documentation/devicetree/bindings/pwm/lpc1850-pwm.txt
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/pwm/lpc1850-pwm.txt b/Documentation/devicetree/bindings/pwm/lpc1850-pwm.txt
>>>> new file mode 100644
>>>> index 0000000..3055429
>>>> --- /dev/null
>>>> +++ b/Documentation/devicetree/bindings/pwm/lpc1850-pwm.txt
>>>> @@ -0,0 +1,20 @@
>>>> +* NXP LPC18xx Pulse Width Modulator driver
>>>> +
>>>> +Required properties:
>>>> +  - compatible: Should be "nxp,lpc1850-pwm"
>>>> +  - reg: Should contain physical base address and length of pwm registers.
>>>> +  - clocks: Must contain an entry for each entry in clock-names.
>>>> +    See ../clock/clock-bindings.txt for details.
>>>> +  - clock-names: Must include the following entries.
>>>> +    - pwm: PWM operating clock.
>>>> +  - #pwm-cells: Should be 3. See pwm.txt in this directory for the description
>>>> +    of the cells format.
>>>> +
>>>> +Example:
>>>> +  pwm: pwm at 40000000 {
>>>> +    compatible = "nxp,lpc1850-pwm";
>>>
>>> I would prefer "nxp,lpc1850-sct" for a couple of reasons. SCT is the
>>> name of hardware block as described in the user manual and while PWM
>>> is the most obvious usage for this block on Linux, the hardware is not
>>> limited to just doing that. So as a bit of future proofing if someone
>>> wants to use this block for more than PWM I would prefer SCT.
>>>
>>
>> Shouldn't we use something like "nxp,lpc1850-sct-pwm"?
>>
>> Sounds like the word PWM should be in the compatible as it describes
>> not only the device, but the device used in a certain way.
>>
>> Otherwise, how would we use "nxp,lpc1850-sct" to distinguish a PWM from
>> e.g. a clocksource/clockevents (we can also use SCT for that)?
>
> I not sure how to best handle dt bindings with such flexible hardware blocks.
>
> But are you suggestion to have multiple drivers for the same hw block?
> ie.: "nxp,lpc1850-sct-pwm" for PWM and for example
> "nxp,lpc1850-sct-clocksource" for clocksource and then use/enable one
> or the other.
>

Yup, I'm suggesting just that. If the hardware is capable, I can't see
why we can't have different drivers for it.

> So I am not sure how to best handle this, but I think we should at
> least consider more than just PWM usage for this hw block. Note that
> not against calling it "lpc1850-sct-pwm", I like that better than just
> "lpc1850-pwm".
>


-- 
Ezequiel García, VanguardiaSur
www.vanguardiasur.com.ar