Messages in this thread | | | Date | Thu, 02 Apr 2015 19:35:46 -0700 | From | Guenter Roeck <> | Subject | Re: [PATCH V2 1/3] watchdog: imgpdc: Allow timeout to be set in device-tree |
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On 04/02/2015 07:16 PM, Andrew Bresticker wrote: > Hi Guenter, > > On Thu, Apr 2, 2015 at 6:52 PM, Guenter Roeck <linux@roeck-us.net> wrote: >> On 04/02/2015 09:46 AM, Andrew Bresticker wrote: >>> >>> On Wed, Apr 1, 2015 at 6:08 PM, Guenter Roeck <linux@roeck-us.net> wrote: >>>> >>>> On 04/01/2015 03:22 PM, James Hogan wrote: >>>>> >>>>> >>>>> Hi Andrew, >>>>> >>>>> On Wed, Apr 01, 2015 at 10:43:14AM -0700, Andrew Bresticker wrote: >>>>>> >>>>>> >>>>>> Since the heartbeat is statically initialized to its default value, >>>>>> watchdog_init_timeout() will never look in the device-tree for a >>>>>> timeout-sec value. Instead of statically initializing heartbeat, >>>>>> fall back to the default timeout value if watchdog_init_timeout() >>>>>> fails. >>>>> >>>>> >>>>> >>>>> Whoops. Sorry about that. I wasn't aware that a timeout-sec value was >>>>> expected. It isn't mentioned in the DT binding documentation for this >>>>> device :-(. >>>>> >>>>>> >>>>>> Signed-off-by: Andrew Bresticker <abrestic@chromium.org> >>>>>> Cc: Ezequiel Garcia <ezequiel.garcia@imgtec.com> >>>>>> Cc: James Hogan <james.hogan@imgtec.com> >>>>>> --- >>>>>> New for v2. >>>>>> --- >>>>>> drivers/watchdog/imgpdc_wdt.c | 6 +++--- >>>>>> 1 file changed, 3 insertions(+), 3 deletions(-) >>>>>> >>>>>> diff --git a/drivers/watchdog/imgpdc_wdt.c >>>>>> b/drivers/watchdog/imgpdc_wdt.c >>>>>> index 0deaa4f..89b2abc 100644 >>>>>> --- a/drivers/watchdog/imgpdc_wdt.c >>>>>> +++ b/drivers/watchdog/imgpdc_wdt.c >>>>>> @@ -42,7 +42,7 @@ >>>>>> #define PDC_WDT_MIN_TIMEOUT 1 >>>>>> #define PDC_WDT_DEF_TIMEOUT 64 >>>>>> >>>>>> -static int heartbeat = PDC_WDT_DEF_TIMEOUT; >>>>>> +static int heartbeat; >>>>>> module_param(heartbeat, int, 0); >>>>>> MODULE_PARM_DESC(heartbeat, "Watchdog heartbeats in seconds " >>>>>> "(default=" __MODULE_STRING(PDC_WDT_DEF_TIMEOUT) ")"); >>>>>> @@ -195,9 +195,9 @@ static int pdc_wdt_probe(struct platform_device >>>>>> *pdev) >>>>>> >>>>>> ret = watchdog_init_timeout(&pdc_wdt->wdt_dev, heartbeat, >>>>>> &pdev->dev); >>>>>> if (ret < 0) { >>>>>> - pdc_wdt->wdt_dev.timeout = >>>>>> pdc_wdt->wdt_dev.max_timeout; >>>>>> + pdc_wdt->wdt_dev.timeout = PDC_WDT_DEF_TIMEOUT; >>>>> >>>>> >>>>> >>>>> The watchdog_init_timeout kerneldoc comment suggests that the old value >>>>> should be the default timeout, i.e. that timeout should be set to >>>>> PDC_WDT_DEF_TIMEOUT before calling watchdog_init_timeout, rather than >>>>> whenever ret < 0. >>>>> >>>>> Indeed, if heartbeat is set to an invalid non-zero value, >>>>> watchdog_init_timeout will still try and set timeout from DT, but also >>>>> still returns -EINVAL regardless of whether that succeeds, and this >>>>> would incorrectly override the timeout from DT with the hardcoded >>>>> default. >>>>> >>>>>> dev_warn(&pdev->dev, >>>>>> - "Initial timeout out of range! setting max >>>>>> timeout\n"); >>>>>> + "Initial timeout out of range! setting default >>>>>> timeout\n"); >>>>> >>>>> >>>>> >>>>> It feels wrong for a presumably safe & normal situation (i.e. no default >>>>> in DT, which arguably shouldn't contain policy anyway) to show a >>>>> warning, but it can also show due to an invalid module parameter (or >>>>> invalid DT property) which is most definitely justified. >>>>> >>>> >>>> Agreed. I would suggest to leave that part alone and set the default >>>> prior >>>> to calling watchdog_init_timeout(). >>> >>> >>> Yes, but I think James' concern here was that we'd now get a >>> dev_warn() in the normal case where no timeout is specified via module >>> parameter or DT. >>> >> My understanding is that watchdog_init_timeout only returns an error if >> the second parameter is not 0 and invalid, or if the timeout-sec property >> has been provided and is invalid. I am not entirely sure I understand >> why you think this is a problem. Can you please explain ? > > Unless I've gone completely insane, I'm pretty sure this will return > -EINVAL if timeout_parm is 0 and timeout-sec is not present: > > int watchdog_init_timeout(struct watchdog_device *wdd, > unsigned int timeout_parm, struct device *dev) > { > unsigned int t = 0; > int ret = 0; > > watchdog_check_min_max_timeout(wdd); > > /* try to get the timeout module parameter first */ > if (!watchdog_timeout_invalid(wdd, timeout_parm) && timeout_parm) { > wdd->timeout = timeout_parm; > return ret; > } > if (timeout_parm) > ret = -EINVAL; > > /* try to get the timeout_sec property */ > if (dev == NULL || dev->of_node == NULL) > return ret; > of_property_read_u32(dev->of_node, "timeout-sec", &t); > if (!watchdog_timeout_invalid(wdd, t) && t) > wdd->timeout = t; > else > ret = -EINVAL; > > return ret; > } > > That said, the behavior you describe makes more sense, so perhaps > watchdog_init_timeout() should be updated to match. >
Ah yes, you are right, that last else case. Guess we'll need input from Wim on how to handle this.
Guenter
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