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Message-ID: <5672D572.9080104@roeck-us.net> Date: Thu, 17 Dec 2015 07:32:02 -0800 From: Guenter Roeck <linux@...ck-us.net> To: Tim Harvey <tharvey@...eworks.com>, Wim Van Sebroeck <wim@...ana.be> Cc: 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 12/17/2015 07:02 AM, Tim Harvey wrote: > 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? > Tim, Do you have an Ack from a devicetree maintainer ? I don't recall seeing one. Thanks, Guenter -- 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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