From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934572AbeEWTfa (ORCPT ); Wed, 23 May 2018 15:35:30 -0400 Received: from mail-qk0-f194.google.com ([209.85.220.194]:42434 "EHLO mail-qk0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934239AbeEWTf0 (ORCPT ); Wed, 23 May 2018 15:35:26 -0400 X-Google-Smtp-Source: ADUXVKLEUTi16uz9VB8O/axwczK46O6Dwh4vKDanxKEhrl0KIZVdRaXvH/GrBgN7tDcWkqEb1BYrXw== Subject: Re: [PATCH 3/5] watchdog: sp805: set WDOG_HW_RUNNING when appropriate To: Guenter Roeck , Robin Murphy Cc: Scott Branden , Mark Rutland , devicetree@vger.kernel.org, linux-watchdog@vger.kernel.org, Catalin Marinas , Will Deacon , linux-kernel@vger.kernel.org, Rob Herring , bcm-kernel-feedback-list@broadcom.com, Wim Van Sebroeck , Frank Rowand , linux-arm-kernel@lists.infradead.org References: <1527014840-21236-1-git-send-email-ray.jui@broadcom.com> <1527014840-21236-4-git-send-email-ray.jui@broadcom.com> <20180522205457.GA16363@roeck-us.net> <0d92b9e9-a3d1-6e91-8371-b5ed3a83e399@broadcom.com> <00c121ea-d197-93b8-2f56-bcca963f70fb@broadcom.com> <76d47e02-7a5f-3fc2-3905-cd4aa03ac69c@arm.com> <5a996888-d3d3-9ae6-e438-5de4d5e3ea32@broadcom.com> <20180523180920.GB27570@roeck-us.net> From: Ray Jui Message-ID: <4da7f930-2698-3ab5-4fce-50af1eba8af5@broadcom.com> Date: Wed, 23 May 2018 12:35:20 -0700 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 MIME-Version: 1.0 In-Reply-To: <20180523180920.GB27570@roeck-us.net> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Guenter/Robin, On 5/23/2018 11:09 AM, Guenter Roeck wrote: > On Wed, May 23, 2018 at 06:15:14PM +0100, Robin Murphy wrote: >> On 23/05/18 17:29, Ray Jui wrote: >>> Hi Robin, >>> >>> On 5/23/2018 4:48 AM, Robin Murphy wrote: >>>> On 23/05/18 08:52, Scott Branden wrote: >>>>> >>>>> >>>>> On 18-05-22 04:24 PM, Ray Jui wrote: >>>>>> Hi Guenter, >>>>>> >>>>>> On 5/22/2018 1:54 PM, Guenter Roeck wrote: >>>>>>> On Tue, May 22, 2018 at 11:47:18AM -0700, Ray Jui wrote: >>>>>>>> If the watchdog hardware is already enabled during the boot process, >>>>>>>> when the Linux watchdog driver loads, it should reset the >>>>>>>> watchdog and >>>>>>>> tell the watchdog framework. As a result, ping can be generated from >>>>>>>> the watchdog framework, until the userspace watchdog daemon >>>>>>>> takes over >>>>>>>> control >>>>>>>> >>>>>>>> Signed-off-by: Ray Jui >>>>>>>> Reviewed-by: Vladimir Olovyannikov >>>>>>>> >>>>>>>> Reviewed-by: Scott Branden >>>>>>>> --- >>>>>>>>   drivers/watchdog/sp805_wdt.c | 22 ++++++++++++++++++++++ >>>>>>>>   1 file changed, 22 insertions(+) >>>>>>>> >>>>>>>> diff --git a/drivers/watchdog/sp805_wdt.c >>>>>>>> b/drivers/watchdog/sp805_wdt.c >>>>>>>> index 1484609..408ffbe 100644 >>>>>>>> --- a/drivers/watchdog/sp805_wdt.c >>>>>>>> +++ b/drivers/watchdog/sp805_wdt.c >>>>>>>> @@ -42,6 +42,7 @@ >>>>>>>>       /* control register masks */ >>>>>>>>       #define    INT_ENABLE    (1 << 0) >>>>>>>>       #define    RESET_ENABLE    (1 << 1) >>>>>>>> +    #define    ENABLE_MASK    (INT_ENABLE | RESET_ENABLE) >>>>>>>>   #define WDTINTCLR        0x00C >>>>>>>>   #define WDTRIS            0x010 >>>>>>>>   #define WDTMIS            0x014 >>>>>>>> @@ -74,6 +75,18 @@ module_param(nowayout, bool, 0); >>>>>>>>   MODULE_PARM_DESC(nowayout, >>>>>>>>           "Set to 1 to keep watchdog running after device release"); >>>>>>>>   +/* returns true if wdt is running; otherwise returns false */ >>>>>>>> +static bool wdt_is_running(struct watchdog_device *wdd) >>>>>>>> +{ >>>>>>>> +    struct sp805_wdt *wdt = watchdog_get_drvdata(wdd); >>>>>>>> + >>>>>>>> +    if ((readl_relaxed(wdt->base + WDTCONTROL) & ENABLE_MASK) == >>>>>>>> +        ENABLE_MASK) >>>>>>>> +        return true; >>>>>>>> +    else >>>>>>>> +        return false; >>>>>>> >>>>>>>     return !!(readl_relaxed(wdt->base + WDTCONTROL) & ENABLE_MASK)); >>>>>>> >>>>>> >>>>>> Note ENABLE_MASK contains two bits (INT_ENABLE and RESET_ENABLE); >>>>>> therefore, a simple !!(expression) would not work? That is, the >>>>>> masked result needs to be compared against the mask again to ensure >>>>>> both bits are set, right? >>>>> Ray - your original code looks correct to me.  Easier to read and less >>>>> prone to errors as shown in the attempted translation to a single >>>>> statement. >>>> >>>>      if () >>>>          return true; >>>>      else >>>>          return false; >>>> >>>> still looks really dumb, though, and IMO is actually harder to read than >>>> just "return ;" because it forces you to stop and >>>> double-check that the logic is, in fact, only doing the obvious thing. >>> >>> If you can propose a way to modify my original code above to make it more >>> readable, I'm fine to make the change. >> >> Well, >> >> return readl_relaxed(wdt->base + WDTCONTROL) & ENABLE_MASK == ENABLE_MASK; >> >> would probably be reasonable to anyone other than the 80-column zealots, but >> removing the silly boolean-to-boolean translation idiom really only >> emphasises the fact that it's fundamentally a big complex statement; for >> maximum clarity I'd be inclined to separate the two logical operations (read >> and comparison), e.g.: >> >> u32 wdtcontrol = readl_relaxed(wdt->base + WDTCONTROL); >> >> return wdtcontrol & ENABLE_MASK == ENABLE_MASK; > > == has higher precendence than bitwise &, so this will need ( ), > but otherwise I agree. > Sure. Let me change the code to the following: u32 wdtcontrol = readl_relaxed(wdt->base + WDTCONTROL); return (wdtcontrol & ENABLE_MASK) == ENABLE_MASK; Thanks. Ray >> >> which is still -3 lines vs. the original. >> >>> As I mentioned, I don't think the following change proposed by Guenter >>> will work due to the reason I pointed out: >>> >>> return !!(readl_relaxed(wdt->base + WDTCONTROL) & ENABLE_MASK)); >> >> FWIW, getting the desired result should only need one logical not swapping >> for a bitwise one there: >> >> return !(~readl_relaxed(wdt->base + WDTCONTROL) & ENABLE_MASK); >> >> but that's well into "too clever for its own good" territory ;) > > Yes, that would be confusing. > >> >> Robin.