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Thu, 25 Jun 2020 06:35:19 -0700 (PDT) Subject: Re: [PATCH 2/2] watchdog: rti: tweak min_hw_heartbeat_ms to match initial allowed window To: Tero Kristo , Jan Kiszka , wim@linux-watchdog.org, linux-watchdog@vger.kernel.org Cc: linux-kernel@vger.kernel.org References: <20200624114534.1362-1-t-kristo@ti.com> <20200624114534.1362-3-t-kristo@ti.com> <289c6104-a885-d3c1-c670-a081ebaaf782@siemens.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: <25bf3ed1-5434-9b45-20ae-e1b2cfc5e5c0@roeck-us.net> Date: Thu, 25 Jun 2020 06:35:17 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-watchdog-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-watchdog@vger.kernel.org On 6/25/20 1:32 AM, Tero Kristo wrote: > On 24/06/2020 18:24, Jan Kiszka wrote: >> On 24.06.20 13:45, Tero Kristo wrote: >>> If the RTI watchdog has been started by someone (like bootloader) when >>> the driver probes, we must adjust the initial ping timeout to match the >>> currently running watchdog window to avoid generating watchdog reset. >>> >>> Signed-off-by: Tero Kristo >>> --- >>>   drivers/watchdog/rti_wdt.c | 25 +++++++++++++++++++++++++ >>>   1 file changed, 25 insertions(+) >>> >>> diff --git a/drivers/watchdog/rti_wdt.c b/drivers/watchdog/rti_wdt.c >>> index d456dd72d99a..02ea2b2435f5 100644 >>> --- a/drivers/watchdog/rti_wdt.c >>> +++ b/drivers/watchdog/rti_wdt.c >>> @@ -55,11 +55,13 @@ static int heartbeat; >>>    * @base - base io address of WD device >>>    * @freq - source clock frequency of WDT >>>    * @wdd  - hold watchdog device as is in WDT core >>> + * @min_hw_heartbeat_save - save of the min hw heartbeat value >>>    */ >>>   struct rti_wdt_device { >>>       void __iomem        *base; >>>       unsigned long        freq; >>>       struct watchdog_device    wdd; >>> +    unsigned int        min_hw_heartbeat_save; >>>   }; >>>   static int rti_wdt_start(struct watchdog_device *wdd) >>> @@ -107,6 +109,11 @@ static int rti_wdt_ping(struct watchdog_device *wdd) >>>       /* put watchdog in active state */ >>>       writel_relaxed(WDKEY_SEQ1, wdt->base + RTIWDKEY); >>> +    if (wdt->min_hw_heartbeat_save) { >>> +        wdd->min_hw_heartbeat_ms = wdt->min_hw_heartbeat_save; >>> +        wdt->min_hw_heartbeat_save = 0; >>> +    } >>> + >>>       return 0; >>>   } >>> @@ -201,6 +208,24 @@ static int rti_wdt_probe(struct platform_device *pdev) >>>           goto err_iomap; >>>       } >>> +    if (readl(wdt->base + RTIDWDCTRL) == WDENABLE_KEY) { >>> +        u32 time_left; >>> +        u32 heartbeat; >>> + >>> +        set_bit(WDOG_HW_RUNNING, &wdd->status); >>> +        time_left = rti_wdt_get_timeleft(wdd); >>> +        heartbeat = readl(wdt->base + RTIDWDPRLD); >>> +        heartbeat <<= WDT_PRELOAD_SHIFT; >>> +        heartbeat /= wdt->freq; >>> +        if (time_left < heartbeat / 2) >>> +            wdd->min_hw_heartbeat_ms = 0; >>> +        else >>> +            wdd->min_hw_heartbeat_ms = >>> +                (time_left - heartbeat / 2 + 1) * 1000; >>> + >>> +        wdt->min_hw_heartbeat_save = 11 * heartbeat * 1000 / 20; >>> +    } >>> + >>>       ret = watchdog_register_device(wdd); >>>       if (ret) { >>>           dev_err(dev, "cannot register watchdog device\n"); >>> >> >> This assumes that the bootloader also programmed a 50% window, right? The pending U-Boot patch will do that, but what if that may chance or someone uses a different setup? > > Yes, we assume 50%. I think based on the hw design, 50% is the only sane value to be used, otherwise you just shrink the open window too much and for no apparent reason. > Not sure if that is a valid assumption. Someone who designs a watchdog with such a narrow ping window might as well also use it. The question is if you want to rely on that assumption, or check and change it if needed. Also, I wonder if we should add an API function such as "set_last_hw_keepalive()" to avoid all that complexity. Thanks, Guenter