> -----Original Message----- > From: Timo Kokkonen [mailto:timo.kokkonen@xxxxxxxxxx] > Sent: 2015年4月14日 15:27 > To: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-watchdog@xxxxxxxxxxxxxxx; > boris.brezillon@xxxxxxxxxxxxxxxxxx; Ferre, Nicolas; alexandre.belloni@free- > electrons.com > Cc: Yang, Wenyou; Timo Kokkonen > Subject: [PATCHv6 0/4] watchdog: Extend kernel API and add early_timeout_sec > feature > > The watchdog kernel API is quite limited. It has support for providing generic > device handling, but it doesn't really know anything about the watchdog hardware > or its constraints. The watchdog drivers come with a lot of diversity and their own > set of quirks and constraints. Some of their limitations are not nice for the user > space, so the drivers work around them with all sorts of ad hoc implementations. > > One common pattern is to use kernel timers or work queues to allow longer > timeout parameters than the actual hardware supports. To solve this problem, this > patch set extends the kernel watchdog API with a few parameters that let the core > know more about the watchdog HW and take care about the timeout extending. > > The patch set also implements "early_timeout_sec" feature that is very common > on many production systems where early kernel or user space crashes must lead > to a device reset. Traditional watchdog handling does not allow this as the > watchdog is stopped (fully or emulating stopped state with kernel timers) before > user space opens it for the first time. > > The changes are designed to be taken in use one driver at time. If the driver does > not set the new parameters and call watchdog_init_params(), the watchdog > behavior is exactly the same as before. > > In principle this new API makes it possible for the user space to see every > watchdog hardware to behave the same, at least in terms of watchdog timeouts. > Once the API is in, it should be easier to move even more common behavior out of > the driver code to the watchdog core and make the drivers simpler. This patch set > converts at91sam9_wdt to use the new API. > > Please review and give feedback. Tested on sama5d4ek, it works fine. > > Patch revision history: > > -v6: Fixed some issued based on feedback from Wenyou Yang. The logic > in watchdog_worker() function is now significantly easier to > read. Several errors with stopping and starting the worker are also > now fixed. > > -v5: Re-think the approach to be fully generic. The early_timeout_sec > handling is no longer in the driver but in the watchdog core. As a > result the core needed to gain knowledge about the watchdog > hardware. Appropriate handling is added in the core. The side effect > for this is that drivers using the new extensions can be simplified > a lot and different kinds of watchdog hardware can be made to > behave the same for the user space. > > -v4: Binding documentation is now separated completely from the driver > patch. The documentation no longer makes any assumptions about how > the actual implementation is made, it just describes the actual > behavior the driver should implement in order to satisfy the > requirement. > > - v3: Rename the property to "early-timeout-sec" and use it as a > timeout value that stops the timer in the atmel driver after the > timeout expires. A watchdog.txt is also introduced for documenting > the common watchdog properties, including now this one and > "timeout-sec" property. > > - v2: Rename the property to "enable-early-reset" as the behavior > itself is not atmel specific. This way other drivers are free to > implement same behavior with the same property name. > > - v1: Propose property name "atmle,no-early-timer" for disabling the > timer that keeps the atmel watchdog running until user space opens > the device. > > Timo Kokkonen (4): > watchdog: Extend kernel API to know about HW limitations > watchdog: Allow watchdog to reset device at early boot > devicetree: Document generic watchdog properties > watchdog: at91sam9_wdt: Convert to use new watchdog core extensions > > .../devicetree/bindings/watchdog/watchdog.txt | 20 ++++ > drivers/watchdog/at91sam9_wdt.c | 58 ++-------- > drivers/watchdog/watchdog_core.c | 124 ++++++++++++++++++++- > drivers/watchdog/watchdog_dev.c | 26 ++++- > include/linux/watchdog.h | 24 ++++ > 5 files changed, 201 insertions(+), 51 deletions(-) create mode 100644 > Documentation/devicetree/bindings/watchdog/watchdog.txt > > -- > 2.1.0 Best Regards, Wenyou Yang ?韬{.n?????%??檩??w?{.n???{??h?Ф?塄}?财??j:+v?? ? ???2??璀??摺?囤??z夸z罐?+?????w棹f
