From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754835AbeEWSJY (ORCPT ); Wed, 23 May 2018 14:09:24 -0400 Received: from bh-25.webhostbox.net ([208.91.199.152]:43001 "EHLO bh-25.webhostbox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750866AbeEWSJW (ORCPT ); Wed, 23 May 2018 14:09:22 -0400 Date: Wed, 23 May 2018 11:09:20 -0700 From: Guenter Roeck To: Robin Murphy Cc: Ray Jui , 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 Subject: Re: [PATCH 3/5] watchdog: sp805: set WDOG_HW_RUNNING when appropriate Message-ID: <20180523180920.GB27570@roeck-us.net> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) X-Authenticated_sender: guenter@roeck-us.net X-OutGoing-Spam-Status: No, score=-1.0 X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - bh-25.webhostbox.net X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - roeck-us.net X-Get-Message-Sender-Via: bh-25.webhostbox.net: authenticated_id: guenter@roeck-us.net X-Authenticated-Sender: bh-25.webhostbox.net: guenter@roeck-us.net X-Source: X-Source-Args: X-Source-Dir: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. > > 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.