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Message-ID: <CAJ+vNU2qHQPSJ1KWp_3f3vAdeuOcF0ooZHmHsdafabZLXJv=Bw@mail.gmail.com> Date: Thu, 17 Dec 2015 07:02:08 -0800 From: Tim Harvey <tharvey@...eworks.com> To: Wim Van Sebroeck <wim@...ana.be> Cc: Guenter Roeck <linux@...ck-us.net>, linux-watchdog@...r.kernel.org, Rob Herring <robh+dt@...nel.org>, Pawel Moll <pawel.moll@....com>, Mark Rutland <mark.rutland@....com>, Ian Campbell <ijc+devicetree@...lion.org.uk>, Kumar Gala <galak@...eaurora.org>, "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Shawn Guo <shawnguo@...nel.org>, Sascha Hauer <kernel@...gutronix.de>, Russell King - ARM Linux <linux@....linux.org.uk>, "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, justin.waters@...esys.com, Lucas Stach <l.stach@...gutronix.de>, Fabio Estevam <festevam@...il.com>, Stefan Roese <sr@...x.de>, Akshay Bhat <akshay.bhat@...esys.com> Subject: Re: [PATCH v4 1/2] watchdog: imx2_wdt: add external reset support via 'ext-reset-output' dt prop On Wed, Dec 2, 2015 at 12:54 PM, Tim Harvey <tharvey@...eworks.com> wrote: > > On Wed, Dec 2, 2015 at 11:11 AM, Akshay Bhat <akshay.bhat@...esys.com> wrote: > > > > > > On 11/06/2015 05:02 PM, Guenter Roeck wrote: > >> > >> On Fri, Nov 06, 2015 at 11:53:42AM -0800, Tim Harvey wrote: > >>> > >>> On Thu, Nov 5, 2015 at 2:23 PM, Guenter Roeck <linux@...ck-us.net> wrote: > >>>> > >>>> On Thu, Nov 05, 2015 at 04:19:21PM -0500, Akshay Bhat wrote: > >>>>> > >>>>> From: Tim Harvey <tharvey@...eworks.com> > >>>>> > >>>>> The IMX6 watchdog supports assertion of a signal (WDOG_B) which > >>>>> can be pinmux'd to an external pin. This is typically used for boards > >>>>> that > >>>>> have PMIC's in control of the IMX6 power rails. In fact, failure to use > >>>>> such an external reset on boards with external PMIC's can result in > >>>>> various > >>>>> hangs due to the IMX6 not being fully reset [1] as well as the board > >>>>> failing > >>>>> to reset because its PMIC has not been reset to provide adequate > >>>>> voltage for > >>>>> the CPU when coming out of reset at 800Mhz. > >>>>> > >>>>> This uses a new device-tree property 'ext-reset-output' to indicate the > >>>>> board has such a reset and to cause the watchdog to be configured to > >>>>> assert > >>>>> WDOG_B instead of an internal reset both on a watchdog timeout and in > >>>>> system_restart. > >>>>> > >>>>> [1] > >>>>> http://lists.infradead.org/pipermail/linux-arm-kernel/2015-March/333689.html > >>>>> > >>>>> Cc: Lucas Stach <l.stach@...gutronix.de> > >>>>> Signed-off-by: Tim Harvey <tharvey@...eworks.com> > >>>>> --- > >>>>> .../devicetree/bindings/watchdog/fsl-imx-wdt.txt | 2 ++ > >>>>> drivers/watchdog/imx2_wdt.c | 20 > >>>>> ++++++++++++++++++-- > >>>>> 2 files changed, 20 insertions(+), 2 deletions(-) > >>>>> > >>>>> diff --git a/Documentation/devicetree/bindings/watchdog/fsl-imx-wdt.txt > >>>>> b/Documentation/devicetree/bindings/watchdog/fsl-imx-wdt.txt > >>>>> index 8dab6fd..9b89b3a 100644 > >>>>> --- a/Documentation/devicetree/bindings/watchdog/fsl-imx-wdt.txt > >>>>> +++ b/Documentation/devicetree/bindings/watchdog/fsl-imx-wdt.txt > >>>>> @@ -9,6 +9,8 @@ Optional property: > >>>> > >>>> > >>>> properties ? > >>>> > >>>>> - big-endian: If present the watchdog device's registers are > >>>>> implemented > >>>>> in big endian mode, otherwise in native mode(same with CPU), for > >>>>> more > >>>>> detail please see: > >>>>> Documentation/devicetree/bindings/regmap/regmap.txt. > >>>>> +- ext-reset-output: If present the watchdog device is configured to > >>>>> assert its > >>>> > >>>> > >>>> Should that have a vendor prefix ? Also, not sure if "-output" > >>>> has any real value in the property name. "fsl,external-reset", maybe ? > >>> > >>> > >>> Hi Guenter, > >>> > >>> I don't see why a vendor prefix is necessary - its a feature of the > >>> IMX6 watchdog supported by this driver to be able to trigger an > >>> internal chip-level reset and/or an external signal that can be hooked > >>> to additional hardware. > >>> > >> Sounded like vendor specific to me, but then I am not a devicetree > >> maintainer, > >> so I am not an authority on the subject. > > > > > > Devicetree maintainers, > > > > Any thoughts? > > > > Tim, > > > > After looking at all the other watchdog drivers, it does not appear that > > there is any other processor which uses a similar feature. Since imx is the > > only processor that appears to support this feature, it might make sense in > > making this vendor specific. If in the future it is found more processors > > support a similar functionality, it can be revisited and moved out from > > being vendor specific? > > > > I'm certainly no expert on device-tree policy. I understand your > point, but realize that the driver in question is imx2_wdt.c > (compatible = "fsl,imx21-wdt"). This is an IP block inside the silicon > of only Freescale chips, so its not like a future omap chip would be > using this driver - only fsl devices. So why would it need a 'vendor' > property any more than its other properties? > > Regards, > > Tim Wim, Does the lack of response mean overwhelming approval? I haven't heard any valid complaints - what does it take to get this approved? Regards, Tim -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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