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Tue, 28 Jul 2020 07:34:09 -0700 (PDT) Subject: Re: [PATCH 1/2] watchdog: imx7ulp: Strictly follow the sequence for wdog operations To: Anson Huang , 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 Cc: Linux-imx@nxp.com References: <1595918567-2017-1-git-send-email-Anson.Huang@nxp.com> From: Guenter Roeck Autocrypt: addr=linux@roeck-us.net; keydata= xsFNBE6H1WcBEACu6jIcw5kZ5dGeJ7E7B2uweQR/4FGxH10/H1O1+ApmcQ9i87XdZQiB9cpN RYHA7RCEK2dh6dDccykQk3bC90xXMPg+O3R+C/SkwcnUak1UZaeK/SwQbq/t0tkMzYDRxfJ7 nyFiKxUehbNF3r9qlJgPqONwX5vJy4/GvDHdddSCxV41P/ejsZ8PykxyJs98UWhF54tGRWFl 7i1xvaDB9lN5WTLRKSO7wICuLiSz5WZHXMkyF4d+/O5ll7yz/o/JxK5vO/sduYDIlFTvBZDh gzaEtNf5tQjsjG4io8E0Yq0ViobLkS2RTNZT8ICq/Jmvl0SpbHRvYwa2DhNsK0YjHFQBB0FX IdhdUEzNefcNcYvqigJpdICoP2e4yJSyflHFO4dr0OrdnGLe1Zi/8Xo/2+M1dSSEt196rXaC kwu2KgIgmkRBb3cp2vIBBIIowU8W3qC1+w+RdMUrZxKGWJ3juwcgveJlzMpMZNyM1jobSXZ0 VHGMNJ3MwXlrEFPXaYJgibcg6brM6wGfX/LBvc/haWw4yO24lT5eitm4UBdIy9pKkKmHHh7s jfZJkB5fWKVdoCv/omy6UyH6ykLOPFugl+hVL2Prf8xrXuZe1CMS7ID9Lc8FaL1ROIN/W8Vk BIsJMaWOhks//7d92Uf3EArDlDShwR2+D+AMon8NULuLBHiEUQARAQABzTJHdWVudGVyIFJv ZWNrIChMaW51eCBhY2NvdW50KSA8bGludXhAcm9lY2stdXMubmV0PsLBgQQTAQIAKwIbAwYL CQgHAwIGFQgCCQoLBBYCAwECHgECF4ACGQEFAlVcphcFCRmg06EACgkQyx8mb86fmYFg0RAA nzXJzuPkLJaOmSIzPAqqnutACchT/meCOgMEpS5oLf6xn5ySZkl23OxuhpMZTVX+49c9pvBx hpvl5bCWFu5qC1jC2eWRYU+aZZE4sxMaAGeWenQJsiG9lP8wkfCJP3ockNu0ZXXAXwIbY1O1 c+l11zQkZw89zNgWgKobKzrDMBFOYtAh0pAInZ9TSn7oA4Ctejouo5wUugmk8MrDtUVXmEA9 7f9fgKYSwl/H7dfKKsS1bDOpyJlqhEAH94BHJdK/b1tzwJCFAXFhMlmlbYEk8kWjcxQgDWMu GAthQzSuAyhqyZwFcOlMCNbAcTSQawSo3B9yM9mHJne5RrAbVz4TWLnEaX8gA5xK3uCNCeyI sqYuzA4OzcMwnnTASvzsGZoYHTFP3DQwf2nzxD6yBGCfwNGIYfS0i8YN8XcBgEcDFMWpOQhT Pu3HeztMnF3HXrc0t7e5rDW9zCh3k2PA6D2NV4fews9KDFhLlTfCVzf0PS1dRVVWM+4jVl6l HRIAgWp+2/f8dx5vPc4Ycp4IsZN0l1h9uT7qm1KTwz+sSl1zOqKD/BpfGNZfLRRxrXthvvY8 BltcuZ4+PGFTcRkMytUbMDFMF9Cjd2W9dXD35PEtvj8wnEyzIos8bbgtLrGTv/SYhmPpahJA l8hPhYvmAvpOmusUUyB30StsHIU2LLccUPPOwU0ETofVZwEQALlLbQeBDTDbwQYrj0gbx3bq 7kpKABxN2MqeuqGr02DpS9883d/t7ontxasXoEz2GTioevvRmllJlPQERVxM8gQoNg22twF7 pB/zsrIjxkE9heE4wYfN1AyzT+AxgYN6f8hVQ7Nrc9XgZZe+8IkuW/Nf64KzNJXnSH4u6nJM J2+Dt274YoFcXR1nG76Q259mKwzbCukKbd6piL+VsT/qBrLhZe9Ivbjq5WMdkQKnP7gYKCAi pNVJC4enWfivZsYupMd9qn7Uv/oCZDYoBTdMSBUblaLMwlcjnPpOYK5rfHvC4opxl+P/Vzyz 6WC2TLkPtKvYvXmdsI6rnEI4Uucg0Au/Ulg7aqqKhzGPIbVaL+U0Wk82nz6hz+WP2ggTrY1w ZlPlRt8WM9w6WfLf2j+PuGklj37m+KvaOEfLsF1v464dSpy1tQVHhhp8LFTxh/6RWkRIR2uF I4v3Xu/k5D0LhaZHpQ4C+xKsQxpTGuYh2tnRaRL14YMW1dlI3HfeB2gj7Yc8XdHh9vkpPyuT nY/ZsFbnvBtiw7GchKKri2gDhRb2QNNDyBnQn5mRFw7CyuFclAksOdV/sdpQnYlYcRQWOUGY HhQ5eqTRZjm9z+qQe/T0HQpmiPTqQcIaG/edgKVTUjITfA7AJMKLQHgp04Vylb+G6jocnQQX JqvvP09whbqrABEBAAHCwWUEGAECAA8CGwwFAlVcpi8FCRmg08MACgkQyx8mb86fmYHNRQ/+ J0OZsBYP4leJvQF8lx9zif+v4ZY/6C9tTcUv/KNAE5leyrD4IKbnV4PnbrVhjq861it/zRQW cFpWQszZyWRwNPWUUz7ejmm9lAwPbr8xWT4qMSA43VKQ7ZCeTQJ4TC8kjqtcbw41SjkjrcTG wF52zFO4bOWyovVAPncvV9eGA/vtnd3xEZXQiSt91kBSqK28yjxAqK/c3G6i7IX2rg6pzgqh hiH3/1qM2M/LSuqAv0Rwrt/k+pZXE+B4Ud42hwmMr0TfhNxG+X7YKvjKC+SjPjqp0CaztQ0H nsDLSLElVROxCd9m8CAUuHplgmR3seYCOrT4jriMFBtKNPtj2EE4DNV4s7k0Zy+6iRQ8G8ng QjsSqYJx8iAR8JRB7Gm2rQOMv8lSRdjva++GT0VLXtHULdlzg8VjDnFZ3lfz5PWEOeIMk7Rj trjv82EZtrhLuLjHRCaG50OOm0hwPSk1J64R8O3HjSLdertmw7eyAYOo4RuWJguYMg5DRnBk WkRwrSuCn7UG+qVWZeKEsFKFOkynOs3pVbcbq1pxbhk3TRWCGRU5JolI4ohy/7JV1TVbjiDI HP/aVnm6NC8of26P40Pg8EdAhajZnHHjA7FrJXsy3cyIGqvg9os4rNkUWmrCfLLsZDHD8FnU mDW4+i+XlNFUPUYMrIKi9joBhu18ssf5i5Q= Message-ID: <566adde7-c397-72f1-145d-fbca9de77cd7@roeck-us.net> Date: Tue, 28 Jul 2020 07:34:07 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <1595918567-2017-1-git-send-email-Anson.Huang@nxp.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Thanks, Guenter > +} > + > static void imx7ulp_wdt_enable(struct watchdog_device *wdog, bool enable) > { > struct imx7ulp_wdt_device *wdt = watchdog_get_drvdata(wdog); > > u32 val = readl(wdt->base + WDOG_CS); > > + local_irq_disable(); > writel(UNLOCK, wdt->base + WDOG_CNT); > + imx7ulp_wdt_wait(wdt->base, WDOG_CS_ULK); > if (enable) > writel(val | WDOG_CS_EN, wdt->base + WDOG_CS); > else > writel(val & ~WDOG_CS_EN, wdt->base + WDOG_CS); > + imx7ulp_wdt_wait(wdt->base, WDOG_CS_RCS); > + local_irq_enable(); > } > > static bool imx7ulp_wdt_is_enabled(void __iomem *base) > @@ -72,7 +88,12 @@ static int imx7ulp_wdt_ping(struct watchdog_device *wdog) > { > struct imx7ulp_wdt_device *wdt = watchdog_get_drvdata(wdog); > > + local_irq_disable(); > + writel(UNLOCK, wdt->base + WDOG_CNT); > + imx7ulp_wdt_wait(wdt->base, WDOG_CS_ULK); > writel(REFRESH, wdt->base + WDOG_CNT); > + imx7ulp_wdt_wait(wdt->base, WDOG_CS_RCS); > + local_irq_enable(); > > return 0; > } > @@ -98,8 +119,12 @@ static int imx7ulp_wdt_set_timeout(struct watchdog_device *wdog, > struct imx7ulp_wdt_device *wdt = watchdog_get_drvdata(wdog); > u32 val = WDOG_CLOCK_RATE * timeout; > > + local_irq_disable(); > writel(UNLOCK, wdt->base + WDOG_CNT); > + imx7ulp_wdt_wait(wdt->base, WDOG_CS_ULK); > writel(val, wdt->base + WDOG_TOVAL); > + imx7ulp_wdt_wait(wdt->base, WDOG_CS_RCS); > + local_irq_enable(); > > wdog->timeout = timeout; > > @@ -140,15 +165,19 @@ static void imx7ulp_wdt_init(void __iomem *base, unsigned int timeout) > { > u32 val; > > + local_irq_disable(); > /* unlock the wdog for reconfiguration */ > writel_relaxed(UNLOCK_SEQ0, base + WDOG_CNT); > writel_relaxed(UNLOCK_SEQ1, base + WDOG_CNT); > + imx7ulp_wdt_wait(base, WDOG_CS_ULK); > > /* set an initial timeout value in TOVAL */ > writel(timeout, base + WDOG_TOVAL); > /* enable 32bit command sequence and reconfigure */ > val = WDOG_CS_CMD32EN | WDOG_CS_CLK | WDOG_CS_UPDATE; > writel(val, base + WDOG_CS); > + imx7ulp_wdt_wait(base, WDOG_CS_RCS); > + local_irq_enable(); > } > > static void imx7ulp_wdt_action(void *data) > From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-12.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A7448C433DF for ; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <1595918567-2017-1-git-send-email-Anson.Huang@nxp.com> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200728_103414_040994_AA9DDD97 X-CRM114-Status: GOOD ( 27.41 ) 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: Linux-imx@nxp.com 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 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. Thanks, Guenter > +} > + > static void imx7ulp_wdt_enable(struct watchdog_device *wdog, bool enable) > { > struct imx7ulp_wdt_device *wdt = watchdog_get_drvdata(wdog); > > u32 val = readl(wdt->base + WDOG_CS); > > + local_irq_disable(); > writel(UNLOCK, wdt->base + WDOG_CNT); > + imx7ulp_wdt_wait(wdt->base, WDOG_CS_ULK); > if (enable) > writel(val | WDOG_CS_EN, wdt->base + WDOG_CS); > else > writel(val & ~WDOG_CS_EN, wdt->base + WDOG_CS); > + imx7ulp_wdt_wait(wdt->base, WDOG_CS_RCS); > + local_irq_enable(); > } > > static bool imx7ulp_wdt_is_enabled(void __iomem *base) > @@ -72,7 +88,12 @@ static int imx7ulp_wdt_ping(struct watchdog_device *wdog) > { > struct imx7ulp_wdt_device *wdt = watchdog_get_drvdata(wdog); > > + local_irq_disable(); > + writel(UNLOCK, wdt->base + WDOG_CNT); > + imx7ulp_wdt_wait(wdt->base, WDOG_CS_ULK); > writel(REFRESH, wdt->base + WDOG_CNT); > + imx7ulp_wdt_wait(wdt->base, WDOG_CS_RCS); > + local_irq_enable(); > > return 0; > } > @@ -98,8 +119,12 @@ static int imx7ulp_wdt_set_timeout(struct watchdog_device *wdog, > struct imx7ulp_wdt_device *wdt = watchdog_get_drvdata(wdog); > u32 val = WDOG_CLOCK_RATE * timeout; > > + local_irq_disable(); > writel(UNLOCK, wdt->base + WDOG_CNT); > + imx7ulp_wdt_wait(wdt->base, WDOG_CS_ULK); > writel(val, wdt->base + WDOG_TOVAL); > + imx7ulp_wdt_wait(wdt->base, WDOG_CS_RCS); > + local_irq_enable(); > > wdog->timeout = timeout; > > @@ -140,15 +165,19 @@ static void imx7ulp_wdt_init(void __iomem *base, unsigned int timeout) > { > u32 val; > > + local_irq_disable(); > /* unlock the wdog for reconfiguration */ > writel_relaxed(UNLOCK_SEQ0, base + WDOG_CNT); > writel_relaxed(UNLOCK_SEQ1, base + WDOG_CNT); > + imx7ulp_wdt_wait(base, WDOG_CS_ULK); > > /* set an initial timeout value in TOVAL */ > writel(timeout, base + WDOG_TOVAL); > /* enable 32bit command sequence and reconfigure */ > val = WDOG_CS_CMD32EN | WDOG_CS_CLK | WDOG_CS_UPDATE; > writel(val, base + WDOG_CS); > + imx7ulp_wdt_wait(base, WDOG_CS_RCS); > + local_irq_enable(); > } > > static void imx7ulp_wdt_action(void *data) > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel