[PATCH 07/13] watchdog: kempld: fix gcc-4.3 build

Arnd Bergmann
2016-12-16T10:55:41Z

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>
---
drivers/watchdog/kempld_wdt.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/watchdog/kempld_wdt.c b/drivers/watchdog/kempld_wdt.c
index 8e302d0e346c..3efa295ac627 100644
--- 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;

--
2.9.0