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 <[email protected]> --- 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
