From: Guenter Roeck <linux@roeck-us.net>
To: Tim Harvey <tharvey@gateworks.com>, Wim Van Sebroeck <wim@iguana.be>
Cc: linux-watchdog@vger.kernel.org, Rob Herring <robh+dt@kernel.org>,
Pawel Moll <pawel.moll@arm.com>,
Mark Rutland <mark.rutland@arm.com>,
Ian Campbell <ijc+devicetree@hellion.org.uk>,
Kumar Gala <galak@codeaurora.org>,
"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Shawn Guo <shawnguo@kernel.org>,
Sascha Hauer <kernel@pengutronix.de>,
Russell King - ARM Linux <linux@arm.linux.org.uk>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
justin.waters@timesys.com, Lucas Stach <l.stach@pengutronix.de>,
Fabio Estevam <festevam@gmail.com>, Stefan Roese <sr@denx.de>,
Akshay Bhat <akshay.bhat@timesys.com>
Subject: Re: [PATCH v4 1/2] watchdog: imx2_wdt: add external reset support via 'ext-reset-output' dt prop
Date: Thu, 17 Dec 2015 07:32:02 -0800 [thread overview]
Message-ID: <5672D572.9080104@roeck-us.net> (raw)
In-Reply-To: <CAJ+vNU2qHQPSJ1KWp_3f3vAdeuOcF0ooZHmHsdafabZLXJv=Bw@mail.gmail.com>
On 12/17/2015 07:02 AM, Tim Harvey wrote:
> On Wed, Dec 2, 2015 at 12:54 PM, Tim Harvey <tharvey@gateworks.com> wrote:
>>
>> On Wed, Dec 2, 2015 at 11:11 AM, Akshay Bhat <akshay.bhat@timesys.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@roeck-us.net> wrote:
>>>>>>
>>>>>> On Thu, Nov 05, 2015 at 04:19:21PM -0500, Akshay Bhat wrote:
>>>>>>>
>>>>>>> From: Tim Harvey <tharvey@gateworks.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@pengutronix.de>
>>>>>>> Signed-off-by: Tim Harvey <tharvey@gateworks.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
next prev parent reply other threads:[~2015-12-17 15:32 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-05 21:19 [PATCH v4 0/2] imx6: Implement external watchdog reset Akshay Bhat
2015-11-05 21:19 ` [PATCH v4 1/2] watchdog: imx2_wdt: add external reset support via 'ext-reset-output' dt prop Akshay Bhat
2015-11-05 22:23 ` Guenter Roeck
2015-11-06 19:53 ` Tim Harvey
2015-11-06 22:02 ` Guenter Roeck
2015-12-02 19:11 ` Akshay Bhat
2015-12-02 20:54 ` Tim Harvey
2015-12-17 15:02 ` Tim Harvey
2015-12-17 15:32 ` Guenter Roeck [this message]
2015-12-28 16:29 ` Wim Van Sebroeck
2016-01-28 20:28 ` Akshay Bhat
2016-02-28 13:56 ` Fabio Estevam
2016-03-28 20:19 ` Akshay Bhat
2016-03-30 1:22 ` Shawn Guo
2016-03-30 21:09 ` Guenter Roeck
2016-03-31 1:57 ` Shawn Guo
2016-03-31 18:01 ` Tim Harvey
2016-04-01 1:39 ` Shawn Guo
2015-11-05 21:19 ` [PATCH v4 2/2] ARM: dts: ventana: Add ext-reset support Akshay Bhat
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