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Tue, 28 Jul 2020 21:15:04 -0700 (PDT) Subject: Re: [PATCH V2 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: <1595989227-24700-1-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: <00587a78-8069-4fbd-7e02-b774d541f75a@roeck-us.net> Date: Tue, 28 Jul 2020 21:15:02 -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: <1595989227-24700-1-git-send-email-Anson.Huang@nxp.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-watchdog-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-watchdog@vger.kernel.org On 7/28/20 7:20 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 > --- > Changes since V1: > - use readl_poll_timeout_atomic() instead of usleep_ranges() since IRQ is disabled. > --- > 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..7d2b12e 100644 > --- a/drivers/watchdog/imx7ulp_wdt.c > +++ b/drivers/watchdog/imx7ulp_wdt.c > @@ -5,6 +5,7 @@ > > #include > #include > +#include > #include > #include > #include > @@ -36,6 +37,7 @@ > #define DEFAULT_TIMEOUT 60 > #define MAX_TIMEOUT 128 > #define WDOG_CLOCK_RATE 1000 > +#define WDOG_WAIT_TIMEOUT 10000 > > static bool nowayout = WATCHDOG_NOWAYOUT; > module_param(nowayout, bool, 0000); > @@ -48,17 +50,31 @@ struct imx7ulp_wdt_device { > struct clk *clk; > }; > > +static inline void imx7ulp_wdt_wait(void __iomem *base, u32 mask) > +{ > + 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)); I am not a friend of WARN_ON, especially in situations like this. Please explain why this is needed, and why a return of -ETIMEDOUT is not feasible. Also, I do not believe that a 10 milli-second timeout is warranted. This will need to be backed up by the datasheet. 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) >