Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S967035AbbLQPCZ (ORCPT ); Thu, 17 Dec 2015 10:02:25 -0500 Received: from mail-io0-f173.google.com ([209.85.223.173]:34294 "EHLO mail-io0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S966843AbbLQPCI (ORCPT ); Thu, 17 Dec 2015 10:02:08 -0500 MIME-Version: 1.0 In-Reply-To: References: <1446758362-11702-1-git-send-email-akshay.bhat@timesys.com> <1446758362-11702-2-git-send-email-akshay.bhat@timesys.com> <20151105222325.GA26159@roeck-us.net> <20151106220249.GA19791@roeck-us.net> <565F4244.7090502@timesys.com> Date: Thu, 17 Dec 2015 07:02:08 -0800 Message-ID: Subject: Re: [PATCH v4 1/2] watchdog: imx2_wdt: add external reset support via 'ext-reset-output' dt prop From: Tim Harvey To: Wim Van Sebroeck Cc: Guenter Roeck , linux-watchdog@vger.kernel.org, Rob Herring , Pawel Moll , Mark Rutland , Ian Campbell , Kumar Gala , "devicetree@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Shawn Guo , Sascha Hauer , Russell King - ARM Linux , "linux-arm-kernel@lists.infradead.org" , justin.waters@timesys.com, Lucas Stach , Fabio Estevam , Stefan Roese , Akshay Bhat Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4523 Lines: 119 On Wed, Dec 2, 2015 at 12:54 PM, Tim Harvey wrote: > > On Wed, Dec 2, 2015 at 11:11 AM, Akshay Bhat 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 wrote: > >>>> > >>>> On Thu, Nov 05, 2015 at 04:19:21PM -0500, Akshay Bhat wrote: > >>>>> > >>>>> From: Tim Harvey > >>>>> > >>>>> 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 > >>>>> Signed-off-by: Tim Harvey > >>>>> --- > >>>>> .../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@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/