Re: [PATCH RESEND V2 1/4] dt-bindings: fsl: scu: add watchdog binding

[Guenter Roeck]

On 2/23/19 7:04 PM, Anson Huang wrote:
> Hi, Guenter/Rob
>
> Best Regards!
> Anson Huang
>
> > -----Original Message-----
> > From: Guenter Roeck [mailto:groeck7@xxxxxxxxx] On Behalf Of Guenter
> > Roeck
> > Sent: 2019å2æ24æ 1:08
> > To: Rob Herring <robh@xxxxxxxxxx>; Anson Huang <anson.huang@xxxxxxx>
> > Cc: mark.rutland@xxxxxxx; shawnguo@xxxxxxxxxx;
> > s.hauer@xxxxxxxxxxxxxx; kernel@xxxxxxxxxxxxxx; festevam@xxxxxxxxx;
> > catalin.marinas@xxxxxxx; will.deacon@xxxxxxx; wim@xxxxxxxxxxxxxxxxxx;
> > Aisheng Dong <aisheng.dong@xxxxxxx>; ulf.hansson@xxxxxxxxxx; Daniel
> > Baluta <daniel.baluta@xxxxxxx>; Andy Gross <andy.gross@xxxxxxxxxx>;
> > horms+renesas@xxxxxxxxxxxx; heiko@xxxxxxxxx; arnd@xxxxxxxx;
> > bjorn.andersson@xxxxxxxxxx; jagan@xxxxxxxxxxxxxxxxxxxx;
> > enric.balletbo@xxxxxxxxxxxxx; marc.w.gonzalez@xxxxxxx; olof@xxxxxxxxx;
> > devicetree@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; linux-arm-
> > kernel@xxxxxxxxxxxxxxxxxxx; linux-watchdog@xxxxxxxxxxxxxxx; dl-linux-imx
> > <linux-imx@xxxxxxx>
> > Subject: Re: [PATCH RESEND V2 1/4] dt-bindings: fsl: scu: add watchdog
> > binding
> >
> > On 2/22/19 11:52 AM, Rob Herring wrote:
> > > On Mon, Feb 18, 2019 at 06:53:48AM +0000, Anson Huang wrote:
> > > > Add i.MX8QXP system controller watchdog binding.
> > > >
> > > > Signed-off-by: Anson Huang <Anson.Huang@xxxxxxx>
> > > > ---
> > > > Changes since V1:
> > > > 	- update dts node name to "watchdog";
> > > > ---
> > > >    Documentation/devicetree/bindings/arm/freescale/fsl,scu.txt | 10
> > ++++++++++
> > > >    1 file changed, 10 insertions(+)
> > > >
> > > > diff --git
> > > > a/Documentation/devicetree/bindings/arm/freescale/fsl,scu.txt
> > > > b/Documentation/devicetree/bindings/arm/freescale/fsl,scu.txt
> > > > index 4b79751..f388ec6 100644
> > > > --- a/Documentation/devicetree/bindings/arm/freescale/fsl,scu.txt
> > > > +++ b/Documentation/devicetree/bindings/arm/freescale/fsl,scu.txt
> > > > @@ -136,6 +136,12 @@ Required properties:
> > > >    			   resource id for thermal driver to get temperature
> > via
> > > >    			   SCU IPC.
> > > >
> > > > +Watchdog bindings based on SCU Message Protocol
> > > > +------------------------------------------------------------
> > > > +
> > > > +Required properties:
> > > > +- compatible: should be "fsl,imx8qxp-sc-wdt";
> > > > +
> > > >    Example (imx8qxp):
> > > >    -------------
> > > >    lsio_mu1: mailbox@5d1c0000 {
> > > > @@ -188,6 +194,10 @@ firmware {
> > > >    			tsens-num = <1>;
> > > >    			#thermal-sensor-cells = <1>;
> > > >    		};
> > > > +
> > > > +		watchdog: watchdog {
> > > > +			compatible = "fsl,imx8qxp-sc-wdt";
> > >
> > > As-is, there's no reason for this to be in DT. The parent node's
> > > driver can instantiate the wdog.
> >
> > As the driver is currently written, you are correct, since it doesn't accept
> > watchdog timeout configuration through devicetree.
> >
> > Question is if that is intended. Is it ?
>
> I am a little confused, do you mean we no need to have "watchdog" node in side "scu"
> node? Or we need to modify the watchdog node's compatible string to " fsl,imx-sc-wdt" to make
> it more generic for other platforms? If yes, I can resend the patch series to modify it.
>   

I think Rob suggested that the SCU parent driver should instantiate the watchdog
without explicit watchdog node. That would be possible, but it currently uses
devm_of_platform_populate() to do the instantiation, and changing that would
be a mess. Besides, it does sem to me that your suggested node would describe
the hardware, so I am not sure I understand the reasoning.

For my part I referred to
	watchdog_init_timeout(imx_sc_wdd, DEFAULT_TIMEOUT, &pdev->dev);
in the driver, which guarantees that the timeout property will not be used
to set the timeout. A more common implementation would have been

	imx_sc_wdd->timeout = DEFAULT_TIMEOUT;
	ret = watchdog_init_timeout(imx_sc_wdd, timeout, &pdev->dev);

where 'timeout' is the module parameter. Which is actually not used in your driver.
Hmm ... I wasn't careful enough with my review. The timeout initialization as-is
doesn't make sense. I'll comment on that in the patch.

Guenter

> Anson.
>
> > Thanks,
> > Guenter