linux-kernel - Re: [PATCH 3/5] watchdog: sp805: set WDOG_HW

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Date:   Wed, 23 May 2018 11:06:39 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Robin Murphy <robin.murphy@....com>
Cc:     Scott Branden <scott.branden@...adcom.com>,
        Ray Jui <ray.jui@...adcom.com>,
        Mark Rutland <mark.rutland@....com>,
        devicetree@...r.kernel.org, linux-watchdog@...r.kernel.org,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        linux-kernel@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
        bcm-kernel-feedback-list@...adcom.com,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Frank Rowand <frowand.list@...il.com>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 3/5] watchdog: sp805: set WDOG_HW_RUNNING when appropriate

On Wed, May 23, 2018 at 12:48:10PM +0100, 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 <ray.jui@...adcom.com>
> >>>>Reviewed-by: Vladimir Olovyannikov <vladimir.olovyannikov@...adcom.com>
> >>>>Reviewed-by: Scott Branden <scott.branden@...adcom.com>
> >>>>---
> >>>>  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 (<boolean condition>)
> 		return true;
> 	else
> 		return false;
> 
> still looks really dumb, though, and IMO is actually harder to read than
> just "return <boolean condition>;" because it forces you to stop and
> double-check that the logic is, in fact, only doing the obvious thing.
> 

Yes, and I won't accept it, sorry.

Guenter

> Robin.
> 
> 
> 
> p.s. No thanks for making me remember the mind-boggling horror of briefly
> maintaining part of this legacy codebase... :P
> 
> $ grep -r '? true : false' --include=*.cpp . | wc -l
> 951