On Sun, Mar 04, 2018 at 07:26:56PM +0300, Ильяс Гасанов wrote: > Hello, > > We (the development team at my current employer company) are having a > specific case of hardware configuraton. Namely, the same GPIO pin is > used for both watchdog keepalive signaling and status LED blinking. > The thing is, there are multiple blinking frequency modes for this > LED, each with its own meaning (i.e. system/firmware states), so > there's a need for changing the frequency/period dynamically from > userspace. > > Previously I've done the thing implementing the timer period > configuration by updating a special sysfs file with new values in the > gpio_wdt driver. However since recently (commit 03bca15 in the kernel > Git repo) the timer has been swapped out with the keepalive callback > thing, which, as far as I can tell, supports updating the timeout > period via the WDIOC_SETTIMEOUT ioctl. However this ioctl is > insufficient for our purposes, in the sense that its minimum > resolution is 1 whole second, while we need a 100 millisecond > granularity at the very most. > > I could also simply disable the gpio_wdt altogether and just use a LED > trigger driven configuration, but I highly doubt this would be a wise > thing, since the whole point of the watchdog is monitoring > responsiveness of the userspace. Also I gather that controlling the > GPIO entirely from a userspace process is rather undesirable, too, as > it might lead to confusing latencies sometimes, for a start. > > I'd like to hear your opinions on the preferred way(s) of implementing > this for our product hardware on the most recent kernels, which could > be sent to upstream to secure further backwards compatibility. > Using the same GPIO pin for both watchdog and LEDs seems odd. I don't have a useful idea how to address your problem, sorry. Guenter
