lkml.org 
[lkml]   [2013]   [Mar]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: watchdog: Add Broadcom BCM2708 watchdog timer driver
On Sun, Mar 24, 2013 at 03:06:59PM +0100, Lubomir Rintel wrote:
> 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?
>
I was referring to line continuation aligned with '(', such as

writel_relaxed(PM_PASSWORD | (cur & PM_RSTC_WRCFG_CLR) |
PM_RSTC_WRCFG_FULL_RESET, wdt_regs + PM_RSTC);

I don't recall how deep the indentation was - does that not fit ?

> ...
> > > +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
>
Ok, makes sense.

> ...
> > > +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.
>
Ok.

> ...
> > > + 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.
>
Some user level documentation states that the default timeout for all drivers
would be 60 seconds. Unfortunately, that is not correct, as all drivers do
what they want. I myself use it as a guideline, ie use a 60 seconds default
unless there is a good reason to use another default value (eg if the
chip only supports a lower maximum).

> > > + 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.
>
Excellent!

Thanks,
Guenter


\
 
 \ /
  Last update: 2013-03-24 17:21    [W:0.050 / U:1.052 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site