linux-kernel - Re: [PATCH 1/3] Documentation: dtb: xgene: Add hwmon dts binding documentation

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Date:	Thu, 23 Jun 2016 09:42:02 -0700
From:	Hoan Tran <hotran@....com>
To:	Jassi Brar <jassisinghbrar@...il.com>,
	Rob Herring <robh@...nel.org>
Cc:	Jean Delvare <jdelvare@...e.com>,
	Guenter Roeck <linux@...ck-us.net>,
	Jonathan Corbet <corbet@....net>,
	Ashwin Chaugule <ashwin.chaugule@...aro.org>,
	Duc Dang <dhdang@....com>, Loc Ho <lho@....com>,
	linux-hwmon@...r.kernel.org, linux-doc@...r.kernel.org,
	lkml <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Devicetree List <devicetree@...r.kernel.org>
Subject: Re: [PATCH 1/3] Documentation: dtb: xgene: Add hwmon dts binding documentation

On Tue, Jun 7, 2016 at 11:05 AM, Hoan Tran <hotran@....com> wrote:
> Hi Jassi,
>
> Thanks for your reply !
>
> On Tue, Jun 7, 2016 at 10:20 AM, Jassi Brar <jassisinghbrar@...il.com> wrote:
>> On Tue, May 24, 2016 at 6:31 AM, Hoan Tran <hotran@....com> wrote:
>>> Hi Rob,
>>>
>>> Thanks for your review !
>>>
>>> On Mon, May 23, 2016 at 1:30 PM, Rob Herring <robh@...nel.org> wrote:
>>>>
>>>> On Mon, May 16, 2016 at 09:17:25AM -0700, Hoan Tran wrote:
>>>> > This patch adds the APM X-Gene hwmon device tree node documentation.
>>>> >
>>>> > Signed-off-by: Hoan Tran <hotran@....com>
>>>> > ---
>>>> >  .../devicetree/bindings/hwmon/apm-xgene-hwmon.txt          | 14 ++++++++++++++
>>>> >  1 file changed, 14 insertions(+)
>>>> >  create mode 100644 Documentation/devicetree/bindings/hwmon/apm-xgene-hwmon.txt
>>>> >
>>>> > diff --git a/Documentation/devicetree/bindings/hwmon/apm-xgene-hwmon.txt b/Documentation/devicetree/bindings/hwmon/apm-xgene-hwmon.txt
>>>> > new file mode 100644
>>>> > index 0000000..49a482e
>>>> > --- /dev/null
>>>> > +++ b/Documentation/devicetree/bindings/hwmon/apm-xgene-hwmon.txt
>>>> > @@ -0,0 +1,14 @@
>>>> > +APM X-Gene hwmon driver
>>>> > +
>>>> > +Hwmon driver accesses sensors over the "SLIMpro" mailbox.
>>>>
>>>> DT bindings describe h/w, not driver data.
>>> How about this description: "APM X-Gene SOC sensors are accessed over
>>> the "SLIMpro" mailbox" ?
>>>> I'm not sure this belongs in
>>>> DT and perhaps the devices for the mailbox should be created by the
>>>> mailbox driver.
>>> I don't think the current mailbox supports it.
>>>>
>>>> > +
>>>> > +Required properties :
>>>> > + - compatible : should be "apm,xgene-slimpro-hwmon"
>>>> > + - mboxes : use the label reference for the mailbox as the first parameter.
>>>> > +         The second parameter is the channel number.
>>>>
>>>> When do you expect this to be different mailbox numbers?
>>> No, this number is not changed. This "mboxes" property is used and
>>> required by mailbox.c when hwmon driver requests a mailbox channel
>>>
>> I think that's inaccurate.
>>
>> The h/w and the firmware combined is the "platform" from Linux POV.
>> Channels are physical resources provided by a mailbox controller.
>> Currently the firmware listens on Channel-7 but some future revision
>> might switch to, say, Channel-9.  Or say the same firmware on next
>> revision of h/w may have to switch to Channel-3 because it has only 4
>> channels. So I see the mailbox channel number as a hardware property
>> just like an IRQ (which very often change with SoC iterations).
>
> Agree about that. I suppose this number is not changed. But as you
> said, the mailbox channel number can be changed based on SoC or
> Firmware. It would be better if this channel number is specified
> inside a DT node.
>
> Hi Rob, do you have any comments ?
>
> Thanks
> Hoan
>
>>
>> Cheers.

Hi Rob,

Do you have any comments on Jassi's reply ?
If not, I'll send another version which included the binding document
and DT node.

Thanks
Hoan