I noticed a build error in some randconfig builds in the zl10353 driver:
dvb-frontends/zl10353.c:138: undefined reference to `____ilog2_NaN'
dvb-frontends/zl10353.c:138: undefined reference to `__aeabi_uldivmod'
The problem can be tracked down to the use of -fprofile-arcs (using
CONFIG_GCOV_PROFILE_ALL) in combination with CONFIG_PROFILE_ALL_BRANCHES
on gcc version 4.9 or higher, when it fails to reliably optimize
constant expressions.
Using div_u64() instead of do_div() makes the code slightly more
readable by both humans and by gcc, which gives the compiler enough
of a break to figure it all out.
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
---
drivers/media/dvb-frontends/zl10353.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/drivers/media/dvb-frontends/zl10353.c b/drivers/media/dvb-frontends/zl10353.c
index ef9764a02d4c..160c88710553 100644
--- a/drivers/media/dvb-frontends/zl10353.c
+++ b/drivers/media/dvb-frontends/zl10353.c
@@ -135,8 +135,7 @@ static void zl10353_calc_nominal_rate(struct dvb_frontend *fe,
value = (u64)10 * (1 << 23) / 7 * 125;
value = (bw * value) + adc_clock / 2;
- do_div(value, adc_clock);
- *nominal_rate = value;
+ *nominal_rate = div_u64(value, adc_clock);
dprintk("%s: bw %d, adc_clock %d => 0x%x\n",
__func__, bw, adc_clock, *nominal_rate);
@@ -163,8 +162,7 @@ static void zl10353_calc_input_freq(struct dvb_frontend *fe,
if (ife > adc_clock / 2)
ife = adc_clock - ife;
}
- value = (u64)65536 * ife + adc_clock / 2;
- do_div(value, adc_clock);
+ value = div_u64((u64)65536 * ife + adc_clock / 2, adc_clock);
*input_freq = -value;
dprintk("%s: if2 %d, ife %d, adc_clock %d => %d / 0x%x\n",
--
2.7.0
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