watchdog: kempld: fix gcc-4.3 build

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>

diff --git a/drivers/watchdog/kempld_wdt.c b/drivers/watchdog/kempld_wdt.c
index 73c46b3a09ab3ec80db0bfb7577fe289fc811b51..2f3b049ea3017c9c481e54b64610975830cdf25d 100644 (file)
--- a/drivers/watchdog/kempld_wdt.c
+++ b/drivers/watchdog/kempld_wdt.c
@@ -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;