Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752235AbbDCCQK (ORCPT ); Thu, 2 Apr 2015 22:16:10 -0400 Received: from mail-qg0-f44.google.com ([209.85.192.44]:36301 "EHLO mail-qg0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750771AbbDCCQH (ORCPT ); Thu, 2 Apr 2015 22:16:07 -0400 MIME-Version: 1.0 In-Reply-To: <551DF27A.6060704@roeck-us.net> References: <1427910196-28568-1-git-send-email-abrestic@chromium.org> <20150401222218.GB13077@jhogan-linux.le.imgtec.org> <551C96AA.2060906@roeck-us.net> <551DF27A.6060704@roeck-us.net> Date: Thu, 2 Apr 2015 19:16:06 -0700 X-Google-Sender-Auth: yU4J25lQuZTIq6v-Y0mX6BGmwlE Message-ID: Subject: Re: [PATCH V2 1/3] watchdog: imgpdc: Allow timeout to be set in device-tree From: Andrew Bresticker To: Guenter Roeck Cc: James Hogan , Wim Van Sebroeck , "linux-watchdog@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Ezequiel Garcia Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5210 Lines: 143 Hi Guenter, On Thu, Apr 2, 2015 at 6:52 PM, Guenter Roeck wrote: > On 04/02/2015 09:46 AM, Andrew Bresticker wrote: >> >> On Wed, Apr 1, 2015 at 6:08 PM, Guenter Roeck 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 >>>>> Cc: Ezequiel Garcia >>>>> Cc: James Hogan >>>>> --- >>>>> 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. Thanks, Andrew -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/