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Wed, 14 Apr 2021 05:13:03 -0700 (PDT) Sender: Guenter Roeck Subject: Re: [PATCH V3] watchdog: mtk: support pre-timeout when the bark irq is available To: Wang Qing , Wim Van Sebroeck , Matthias Brugger , linux-watchdog@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org References: <1618400929-17013-1-git-send-email-wangqing@vivo.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: <1e60551b-4961-91d6-1ea8-7e3b6becd385@roeck-us.net> Date: Wed, 14 Apr 2021 05:13:01 -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: <1618400929-17013-1-git-send-email-wangqing@vivo.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/14/21 4:48 AM, Wang Qing wrote: > Use the bark interrupt as the pretimeout notifier if available. > > By default, the pretimeout notification shall occur one second earlier > than the timeout. > > V2: > - panic() by default if WATCHDOG_PRETIMEOUT_GOV is not enabled. > > V3: > - Modify the pretimeout behavior, manually reset after the pretimeout > - is processed and wait until timeout. > > Signed-off-by: Wang Qing > --- > drivers/watchdog/mtk_wdt.c | 62 ++++++++++++++++++++++++++++++++++++++++++---- > 1 file changed, 57 insertions(+), 5 deletions(-) > > diff --git a/drivers/watchdog/mtk_wdt.c b/drivers/watchdog/mtk_wdt.c > index 97ca993..7bef1e3 > --- a/drivers/watchdog/mtk_wdt.c > +++ b/drivers/watchdog/mtk_wdt.c > @@ -25,6 +25,7 @@ > #include > #include > #include > +#include > > #define WDT_MAX_TIMEOUT 31 > #define WDT_MIN_TIMEOUT 1 > @@ -234,18 +235,46 @@ static int mtk_wdt_start(struct watchdog_device *wdt_dev) > void __iomem *wdt_base = mtk_wdt->wdt_base; > int ret; > > - ret = mtk_wdt_set_timeout(wdt_dev, wdt_dev->timeout); > + ret = mtk_wdt_set_timeout(wdt_dev, wdt_dev->timeout - wdt_dev->pretimeout); > if (ret < 0) > return ret; > > reg = ioread32(wdt_base + WDT_MODE); > - reg &= ~(WDT_MODE_IRQ_EN | WDT_MODE_DUAL_EN); > + reg &= ~WDT_MODE_IRQ_EN; > + if (wdt_dev->pretimeout) > + reg |= WDT_MODE_IRQ_EN; > + else > + reg &= ~WDT_MODE_IRQ_EN; > reg |= (WDT_MODE_EN | WDT_MODE_KEY); > iowrite32(reg, wdt_base + WDT_MODE); > > return 0; > } > > +static int mtk_wdt_set_pretimeout(struct watchdog_device *wdd, > + unsigned int timeout) > +{ > + wdd->pretimeout = timeout; > + return mtk_wdt_start(wdd); The watchdog is not necessarily active here. > +} > + > +static irqreturn_t mtk_wdt_isr(int irq, void *arg) > +{ > + struct watchdog_device *wdd = arg; > + struct mtk_wdt_dev *mtk_wdt = watchdog_get_drvdata(wdd); > + void __iomem *wdt_base = mtk_wdt->wdt_base; > + > + watchdog_notify_pretimeout(wdd); > + /* > + * Guaranteed to be reset when the timeout > + * expires under any situations > + */ > + mdelay(1000*wdd->pretimeout); That is not how this is supposed to work. The idea with a pretimeout is that the real watchdog reset will happen under all circumstances, and that executing the pretimeout (and changing some hardware registers) is not a prerequisite for the real timeout to happen. After all, the system could be stuck hard, with interrupts disabled. On top of that, just sleeping here while waiting for the real timeout and then resetting the system isn't the idea either. On a single core system this will just hang. On a multi-core system, who knows if userspace managed to ping the watchdog in the meantime. Unless there is a means to trigger the watchdog twice, without intervention, the first time generating an interrupt and the second time resetting the system, there is no way for this to work. I don't see how this chip really supports pretimeout. It seems that it supports either a hard reset or generating an interrupt on watchdog timeout, and there is only a single timeout. If you have a use case for generating an interrupt and resetting the system via software (ie panic) _instead_ of having it generate a hard reset, please feel free to submit a patch along that line, together with a description of its use case. Thanks, Guenter > + writel(WDT_SWRST_KEY, wdt_base + WDT_SWRST); > + > + return IRQ_HANDLED; > +} > + > static const struct watchdog_info mtk_wdt_info = { > .identity = DRV_NAME, > .options = WDIOF_SETTIMEOUT | > @@ -253,12 +282,21 @@ static const struct watchdog_info mtk_wdt_info = { > WDIOF_MAGICCLOSE, > }; > > +static const struct watchdog_info mtk_wdt_pt_info = { > + .identity = DRV_NAME, > + .options = WDIOF_SETTIMEOUT | > + WDIOF_PRETIMEOUT | > + WDIOF_KEEPALIVEPING | > + WDIOF_MAGICCLOSE, > +}; > + > static const struct watchdog_ops mtk_wdt_ops = { > .owner = THIS_MODULE, > .start = mtk_wdt_start, > .stop = mtk_wdt_stop, > .ping = mtk_wdt_ping, > .set_timeout = mtk_wdt_set_timeout, > + .set_pretimeout = mtk_wdt_set_pretimeout, > .restart = mtk_wdt_restart, > }; > > @@ -267,7 +305,7 @@ static int mtk_wdt_probe(struct platform_device *pdev) > struct device *dev = &pdev->dev; > struct mtk_wdt_dev *mtk_wdt; > const struct mtk_wdt_data *wdt_data; > - int err; > + int err, irq; > > mtk_wdt = devm_kzalloc(dev, sizeof(*mtk_wdt), GFP_KERNEL); > if (!mtk_wdt) > @@ -279,7 +317,22 @@ static int mtk_wdt_probe(struct platform_device *pdev) > if (IS_ERR(mtk_wdt->wdt_base)) > return PTR_ERR(mtk_wdt->wdt_base); > > - mtk_wdt->wdt_dev.info = &mtk_wdt_info; > + irq = platform_get_irq(pdev, 0); > + if (irq > 0) { > + err = devm_request_irq(&pdev->dev, irq, mtk_wdt_isr, 0, "wdt_bark", > + &mtk_wdt->wdt_dev); > + if (err) > + return err; > + > + mtk_wdt->wdt_dev.info = &mtk_wdt_pt_info; > + mtk_wdt->wdt_dev.pretimeout = 1; > + } else { > + if (irq == -EPROBE_DEFER) > + return -EPROBE_DEFER; > + > + mtk_wdt->wdt_dev.info = &mtk_wdt_info; > + } > + > mtk_wdt->wdt_dev.ops = &mtk_wdt_ops; > mtk_wdt->wdt_dev.timeout = WDT_MAX_TIMEOUT; > mtk_wdt->wdt_dev.max_hw_heartbeat_ms = WDT_MAX_TIMEOUT * 1000; > @@ -360,7 +413,6 @@ static struct platform_driver mtk_wdt_driver = { > }; > > module_platform_driver(mtk_wdt_driver); > - > module_param(timeout, uint, 0); > MODULE_PARM_DESC(timeout, "Watchdog heartbeat in seconds"); > >