Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Ken Sloat <KSloat@aampglobal.com>
To:     Alexandre Belloni <alexandre.belloni@bootlin.com>
CC:     Guenter Roeck <linux@roeck-us.net>,
        "nicolas.ferre@microchip.com" <nicolas.ferre@microchip.com>,
        "ludovic.desroches@microchip.com" <ludovic.desroches@microchip.com>,
        "wim@linux-watchdog.org" <wim@linux-watchdog.org>,
        "linux-arm-kernel@lists.infradead.org" 
        <linux-arm-kernel@lists.infradead.org>,
        "linux-watchdog@vger.kernel.org" <linux-watchdog@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH v2 1/1] watchdog: atmel: atmel-sama5d4-wdt: Disable
 watchdog on system suspend
Thread-Topic: [PATCH v2 1/1] watchdog: atmel: atmel-sama5d4-wdt: Disable
 watchdog on system suspend
Thread-Index: AQHVIrAmpSe7ef5LPkq+gtVGV8yaCKabW/WAgAAQIfCAAAbcAIAAAenAgAAmm4CAAADR8A==
Date:   Fri, 14 Jun 2019 20:45:28 +0000
Message-ID: <BL0PR07MB4115721DA2EB445BE7590BF6ADEE0@BL0PR07MB4115.namprd07.prod.outlook.com>
References: <20190614125310.29458-1-ksloat@aampglobal.com>
 <20190614164609.GA29814@roeck-us.net>
 <BL0PR07MB4115E99D065FD9BEA4C43BB5ADEE0@BL0PR07MB4115.namprd07.prod.outlook.com>
 <20190614180826.GD3369@piout.net>
 <BL0PR07MB4115D5ECDEDCC028197637E5ADEE0@BL0PR07MB4115.namprd07.prod.outlook.com>
 <20190614203327.GE3369@piout.net>
In-Reply-To: <20190614203327.GE3369@piout.net>
Accept-Language: en-US
Content-Language: en-US
received-spf: None (protection.outlook.com: aampglobal.com does not designate
 permitted sender hosts)
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
X-MS-Exchange-CrossTenant-Network-Message-Id: ef799d38-ce9a-450a-4553-08d6f1093bfb
X-MS-Exchange-CrossTenant-originalarrivaltime: 14 Jun 2019 20:45:28.0817
 (UTC)
X-MS-Exchange-CrossTenant-fromentityheader: Hosted
X-MS-Exchange-CrossTenant-id: e20e3a66-8b9e-46e9-b859-cb654c1ec6ea
X-MS-Exchange-CrossTenant-mailboxtype: HOSTED
X-MS-Exchange-CrossTenant-userprincipalname: ken.sloat@aampglobal.com
X-MS-Exchange-Transport-CrossTenantHeadersStamped: BL0PR07MB5521
X-MS-Exchange-CrossPremises-AuthAs: Internal
X-MS-Exchange-CrossPremises-AuthMechanism: 04
X-MS-Exchange-CrossPremises-AuthSource: BL0PR07MB4115.namprd07.prod.outlook.com
X-MS-Exchange-CrossPremises-TransportTrafficType: Email
X-MS-Exchange-CrossPremises-TransportTrafficSubType: 
X-MS-Exchange-CrossPremises-SCL: 1
X-MS-Exchange-CrossPremises-messagesource: StoreDriver
X-MS-Exchange-CrossPremises-BCC: 
X-MS-Exchange-CrossPremises-originalclientipaddress: 100.3.71.115
X-MS-Exchange-CrossPremises-transporttraffictype: Email
X-MS-Exchange-CrossPremises-transporttrafficsubtype: 
X-MS-Exchange-CrossPremises-antispam-scancontext: DIR:Originating;SFV:NSPM;SKIP:0;
X-MS-Exchange-CrossPremises-processed-by-journaling: Journal Agent
X-OrganizationHeadersPreserved: BL0PR07MB5521.namprd07.prod.outlook.com
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

> -----Original Message-----
> From: Alexandre Belloni <alexandre.belloni@bootlin.com>
> Sent: Friday, June 14, 2019 4:33 PM
> To: Ken Sloat <KSloat@aampglobal.com>
> Cc: Guenter Roeck <linux@roeck-us.net>; nicolas.ferre@microchip.com;
> ludovic.desroches@microchip.com; wim@linux-watchdog.org; linux-arm-
> kernel@lists.infradead.org; linux-watchdog@vger.kernel.org; linux-
> kernel@vger.kernel.org
> Subject: Re: [PATCH v2 1/1] watchdog: atmel: atmel-sama5d4-wdt: Disable
> watchdog on system suspend
>=20
> [This is an EXTERNAL EMAIL]
> ________________________________
>=20
> On 14/06/2019 18:43:22+0000, Ken Sloat wrote:
> > Well I'm a little confused still because there are two separate
> > comments in these statements. The first within resume implies that the
> > init should be called because we might have lost register values for
> > some reason unexplained.
>=20
> The sama5d2 has a suspend mode where power to the core is completely
> cut. Only a few IPs remain powered (in the backup power domain).
> Unfortunately, the watchdog is not in that domain and may lose its regist=
ers.
>=20
> > Then within the init it says that the bootloader might have modified
> > the registers so we should check them and then update it or otherwise
> > disable it. I'm not trying to pick apart the logic or anything, I'm
> > just readily assuming it is good as it was already reviewed before.
> >
>=20
> The bootloaders may have started the watchdog (this makes sense if you
> really care about reliability) and so we need to be careful to keep the p=
roper
> parameters.

Thanks for the explanation Alexandre I appreciate it.

> > So without digging into that too much, if we don't know if any of the
> > runtime situations above might have occurred, then isn't it best to
> > leave my patch as is? Yes this has the side effect of resetting the
> > timer count, but if the init call is needed and we don't have any way
> > to know if any of the situations occurred, then we have no choice right=
?
> >
>=20
> Until we can differentiate between suspend modes, we have no other
> choice.

Ok I will leave my patch as is for now then

> --
> Alexandre Belloni, Bootlin
> Embedded Linux and Kernel engineering
> https://bootlin.com

Thanks,
Ken Sloat