watchdog: Add Broadcom BCM2708 watchdog timer driver
Lubomir Rintel
lkundrak at v3.sk
Sun Mar 24 10:06:59 EDT 2013
On Fri, 2013-03-22 at 06:56 -0700, Guenter Roeck wrote:
Thank you for your response!
On Fri Mar 22 09:56:01 EDT 2013, Guenter Roeck wrote:
> On Fri, Mar 22, 2013 at 12:55:07PM -0000, Lubomir Rintel wrote:
...
> > + writel_relaxed(PM_PASSWORD | (cur & PM_RSTC_WRCFG_CLR) |
> > + PM_RSTC_WRCFG_FULL_RESET, wdt_regs + PM_RSTC);
> > +
> Nitpick - I prefer people to use the recommended continuation line style,
> but that is really up to the maintainer to decide.
Well, I intended to comply with Documentation/CodingStyle, are you referring to
it? I fail to understand what to do to be more compliant and could not really
identify a style that would be consistently used across the kernel source.
Should I cut then second line into two smaller parts that would be aligned with
right line end?
...
> > +static int bcm2835_wdt_set_timeout(struct watchdog_device *wdog, unsigned int t)
> > +{
> > + wdog->timeout = t;
>
> No need to update the actual chip timeout ?
No need to, watchdog core applies the new timeout by pinging the device (see
below for what happens when this driver is pinged).
See: WDIOC_SETTIMEOUT in drivers/watchdog/watchdog_dev.c
...
> > +static struct watchdog_ops bcm2835_wdt_ops = {
> > + .owner = THIS_MODULE,
> > + .start = bcm2835_wdt_start,
> > + .stop = bcm2835_wdt_stop,
> > + .set_timeout = bcm2835_wdt_set_timeout,
> > + .get_timeleft = bcm2835_wdt_get_timeleft,
>
> No separate ping function ?
The watchdog documentation core states:
"Most hardware that does not support this as a separate function uses the
start function to restart the watchdog timer hardware. And that's also what
the watchdog timer driver core does."
This indeed applies to this driver.
...
> > + if (WARN(!wdt_regs, "failed to remap watchdog regs"))
> > + return -ENODEV;
>
> WARN seems to be a bit extreme. Is this necessary ?
Probably not. I'll replace it with dev_err() instead.
> > + dev_info(dev, "Broadcom BCM2835 watchdog timer");
> > +
> > + watchdog_init_timeout(&bcm2835_wdt_wdd, heartbeat, dev);
>
> Since heartbeat is by default set to -1, which is interpreted as unsigned
> int, I would expect this call to return -EINVAL, leaving the default timeout
> undefined. Is this really what you want ?
Well, I looked into orion-wdt for an example how to initialize the default
timeout, but failed to understand it correctly. I thought that watchdog core
picks a sensible value upon getting -1, which is incorrect. They in fact use
initialize timeout with maximal value, and use a fall-through vi EINVAL to leave
it untouched if it was not overridden. I'll do the same thing now.
> > + watchdog_set_nowayout(&bcm2835_wdt_wdd, nowayout);
> > + return watchdog_register_device(&bcm2835_wdt_wdd);
>
> Leaking iomap if this fails.
Oops. Fixing.
> Would be nice to have something like devm_of_iomap ...
That sounds sound to me. Sent out a separate patch implementing it, and I'll
modify this if it gets merged.
--
Lubomir Rintel <lkundrak at v3.sk>
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