Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757266AbbLBUyV (ORCPT ); Wed, 2 Dec 2015 15:54:21 -0500 Received: from mail-oi0-f53.google.com ([209.85.218.53]:34021 "EHLO mail-oi0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756425AbbLBUyR (ORCPT ); Wed, 2 Dec 2015 15:54:17 -0500 MIME-Version: 1.0 In-Reply-To: <565F4244.7090502@timesys.com> 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: Wed, 2 Dec 2015 12:54:16 -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: Akshay Bhat Cc: Guenter Roeck , linux-watchdog@vger.kernel.org, Rob Herring , Pawel Moll , Mark Rutland , Ian Campbell , Kumar Gala , Wim Van Sebroeck , "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 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: 4089 Lines: 107 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 -- 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/