Re: [PATCH 3/5] watchdog: sp805: set WDOG_HW_RUNNING when appropriate

From: Robin Murphy
Date: Wed May 23 2018 - 06:54:49 EST


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@xxxxxxxxxxxx>
Reviewed-by: Vladimir Olovyannikov <vladimir.olovyannikov@xxxxxxxxxxxx>
Reviewed-by: Scott Branden <scott.branden@xxxxxxxxxxxx>
---
 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 @@
ÂÂÂÂÂ /* control register masks */
ÂÂÂÂÂ #defineÂÂÂ INT_ENABLEÂÂÂ (1 << 0)
ÂÂÂÂÂ #defineÂÂÂ RESET_ENABLEÂÂÂ (1 << 1)
+ÂÂÂ #defineÂÂÂ ENABLE_MASKÂÂÂ (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,
ÂÂÂÂÂÂÂÂÂ "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)
+{
+ÂÂÂ struct sp805_wdt *wdt = watchdog_get_drvdata(wdd);
+
+ÂÂÂ if ((readl_relaxed(wdt->base + WDTCONTROL) & ENABLE_MASK) ==
+ÂÂÂÂÂÂÂ ENABLE_MASK)
+ÂÂÂÂÂÂÂ return true;
+ÂÂÂ else
+ÂÂÂÂÂÂÂ return false;

ÂÂÂÂreturn !!(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.

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