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b=F8T9JCySUxMOmdMscLQfpgHH399FDm0blVYDOoeQkU7MfGWFYiqW+4cHBeeC1QCQ/rgk97SkYF3alyPefqNchCqbdbs0KvXOn0ZzPJludhvnN0ntjwDCC809M6mjOh8gHGvJJq/aAzyh2C1gF7KDEa179ar+tnqfY9xgGxB+RhU= Received: from DB3PR0402MB3916.eurprd04.prod.outlook.com (2603:10a6:8:10::18) by DB6PR0401MB2536.eurprd04.prod.outlook.com (2603:10a6:4:36::23) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3216.26; Wed, 29 Jul 2020 02:26:33 +0000 Received: from DB3PR0402MB3916.eurprd04.prod.outlook.com ([fe80::49f8:20ce:cf20:80b3]) by DB3PR0402MB3916.eurprd04.prod.outlook.com ([fe80::49f8:20ce:cf20:80b3%6]) with mapi id 15.20.3216.034; Wed, 29 Jul 2020 02:26:33 +0000 From: Anson Huang To: Guenter Roeck , "wim@linux-watchdog.org" , "shawnguo@kernel.org" , "s.hauer@pengutronix.de" , "kernel@pengutronix.de" , "festevam@gmail.com" , "linux-watchdog@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" Subject: RE: [PATCH 1/2] watchdog: imx7ulp: Strictly follow the sequence for wdog operations Thread-Topic: [PATCH 1/2] watchdog: imx7ulp: Strictly follow the sequence for wdog operations Thread-Index: AQHWZKrocghDMpUaBEu/lC3XXGngDakdDvaAgACUUzCAADIzYA== Date: Wed, 29 Jul 2020 02:26:33 +0000 Message-ID: References: <1595918567-2017-1-git-send-email-Anson.Huang@nxp.com> <566adde7-c397-72f1-145d-fbca9de77cd7@roeck-us.net> In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: roeck-us.net; dkim=none (message not signed) header.d=none;roeck-us.net; dmarc=none action=none header.from=nxp.com; x-originating-ip: [119.31.174.67] x-ms-publictraffictype: Email x-ms-office365-filtering-ht: Tenant x-ms-office365-filtering-correlation-id: 33e89742-b3f0-4c1d-39f1-08d83366cf88 x-ms-traffictypediagnostic: DB6PR0401MB2536: x-ms-exchange-transport-forked: True x-microsoft-antispam-prvs: x-ms-oob-tlc-oobclassifiers: OLM:10000; x-ms-exchange-senderadcheck: 1 x-microsoft-antispam: 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Bl/JkE3Je4qclvkYpM6xyvqCghHLFmD7bUPO9pO9N4ujWiYprwVQWzhWyrlyv2ZfNUFMkTkavLKnTJDdBoij/zS+lQiJyiuG6Qo+s3VDgGST9SludkdKvY9oAspjTIc0jSGLHZpuFsz3iujQxvUD8uxoi+3H0iiceiotNYGJzuyARJraX9/+1Plkea/jmTcfFf9+t0ZLxnu5xJtjDEYELNQfBMY0NR5O/sdhFWkCqaUvLbMOz1ZTyifA7/imM8yN71MO3QpTyFWbfwwkzmk7l9HBb+WA+SgrSdhPK5j/ZSV38p+VOeFArR6EJ1vddORux5fSZkEyhiQStsawrMRGkUuEGx1lU2DcTlvjmBgpgehB4Vj5B7hn3x0vdozqIY7X5cDgRrie32TS6NTx1UkbWcPDPN541w4mgY/WJJvemR27W5JGO/k5TWO1TIsuwNUMBO+FVEtXDmMbf6GeF8bAjuqQUCtNCvD7WQpL87nxtY4= MIME-Version: 1.0 X-OriginatorOrg: nxp.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: DB3PR0402MB3916.eurprd04.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: 33e89742-b3f0-4c1d-39f1-08d83366cf88 X-MS-Exchange-CrossTenant-originalarrivaltime: 29 Jul 2020 02:26:33.3148 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 686ea1d3-bc2b-4c6f-a92c-d99c5c301635 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: 5FLpL+ov3AWd0EvidSW5IO67a253hpTEaMgHxSkQLDzXFbskXM/eK8TWKyGrwOsuJmh3mmN0iXMKJbH8SFpDeQ== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DB6PR0401MB2536 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200728_222637_101142_AD346E2B X-CRM114-Status: GOOD ( 33.64 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: dl-linux-imx Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi, Guenter > Subject: RE: [PATCH 1/2] watchdog: imx7ulp: Strictly follow the sequence for > wdog operations > > Hi, Guenter > > > > Subject: Re: [PATCH 1/2] watchdog: imx7ulp: Strictly follow the > > sequence for wdog operations > > > > On 7/27/20 11:42 PM, Anson Huang wrote: > > > According to reference manual, the i.MX7ULP WDOG's operations should > > > follow below sequence: > > > > > > 1. disable global interrupts; > > > 2. unlock the wdog and wait unlock bit set; 3. reconfigure the wdog > > > and wait for reconfiguration bit set; 4. enabel global interrupts. > > > > > > Strictly follow the recommended sequence can make it more robust. > > > > > > Signed-off-by: Anson Huang > > > --- > > > drivers/watchdog/imx7ulp_wdt.c | 29 +++++++++++++++++++++++++++++ > > > 1 file changed, 29 insertions(+) > > > > > > diff --git a/drivers/watchdog/imx7ulp_wdt.c > > > b/drivers/watchdog/imx7ulp_wdt.c index 7993c8c..b414ecf 100644 > > > --- a/drivers/watchdog/imx7ulp_wdt.c > > > +++ b/drivers/watchdog/imx7ulp_wdt.c > > > @@ -4,6 +4,7 @@ > > > */ > > > > > > #include > > > +#include > > > #include > > > #include > > > #include > > > @@ -48,17 +49,32 @@ struct imx7ulp_wdt_device { > > > struct clk *clk; > > > }; > > > > > > +static inline void imx7ulp_wdt_wait(void __iomem *base, u32 mask) { > > > + int retries = 100; > > > + > > > + do { > > > + if (readl_relaxed(base + WDOG_CS) & mask) > > > + return; > > > + usleep_range(200, 1000); > > > + } while (retries--); > > > > Sleep with interrupts disabled ? I can not imagine that this works > > well in a single CPU system. On top of that, it seems quite pointless. > > Either you don't want to be interrupted or you do, but sleeping with > > interrupts disabled really doesn't make sense. And does it really take > > 200-1000 uS for the watchdog subsystem to react, and sometimes up to > > 200 * 100 = 20 mS ? That seems highly unlikely. If such a delay loop > > is indeed needed, it should be limited by a time, not by number of > repetitions. > > > > Unless there is evidence that there is a problem that needs to be > > solved, I am not going to accept this code. > > > > Oops, this is a mistake of using sleep with interrupt disabled, sorry for that. > The best option is to use readl_relaxed_poll_timeout_atomic() to poll the > status bit, however, the i.MX7ULP watchdog is very special that the unlock > window ONLY open for several cycles, that means the unlock status bit will be > set and then clear automatically after those cycles, using > readl_relaxed_poll_timeout_atomic() will fail since there are many timeout > handle code in it and the unlock window is open and close during this timeout > handle interval, so it fail to catch the unlock bit. > > The ideal option is using atomic polling without any other timeout check to > make sure the unlock window is NOT missed, but I think Linux kernel will NOT > accept a while loop without timeout, and that is why I tried to use > usleep_ranges(), but obviously I made a mistake of using it with IRQ disabled. > > Do you have any suggestion of how to handle such case? If the hardware ONLY > unlock the register for a small window, how to poll the status bit with timeout > handle and also make sure the timeout handle code as quick as possible to > NOT miss the window? > I did more experiment and found that below readl_poll_timeout_atomic() is actually working, so I sent a V2 with it, please help review, thank you. + u32 val = readl(base + WDOG_CS); + + if (!(val & mask)) + WARN_ON(readl_poll_timeout_atomic(base + WDOG_CS, val, + val & mask, 0, + WDOG_WAIT_TIMEOUT)); Thanks, Anson _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel