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watchdog: kempld: fix gcc-4.3 build

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gcc-4.3 can't decide whether the constant value in
kempld_prescaler[PRESCALER_21] is built-time constant or
not, and gets confused by the logic in do_div():

drivers/watchdog/kempld_wdt.o: In function `kempld_wdt_set_stage_timeout':
kempld_wdt.c:(.text.kempld_wdt_set_stage_timeout+0x130): undefined reference to `__aeabi_uldivmod'

This adds a call to ACCESS_ONCE() to force it to not consider
it to be constant, and leaves the more efficient normal case
in place for modern compilers, using an #ifdef to annotate
why we do this hack.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
This commit is contained in:
Arnd Bergmann 2017-03-01 10:15:29 +01:00 committed by Guenter Roeck
parent 8d5755b3f7
commit 3736d4eb6a
1 changed files with 8 additions and 1 deletions
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9
drivers/watchdog/kempld_wdt.c
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@ -140,12 +140,19 @@ static int kempld_wdt_set_stage_timeout(struct kempld_wdt_data *wdt_data,
unsigned int timeout)
{
struct kempld_device_data *pld = wdt_data->pld;
u32 prescaler = kempld_prescaler[PRESCALER_21];
u32 prescaler;
u64 stage_timeout64;
u32 stage_timeout;
u32 remainder;
u8 stage_cfg;
#if GCC_VERSION < 40400
/* work around a bug compiling do_div() */
prescaler = READ_ONCE(kempld_prescaler[PRESCALER_21]);
#else
prescaler = kempld_prescaler[PRESCALER_21];
#endif
if (!stage)
return -EINVAL;