4.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Slava Shwartsman <slavash@xxxxxxxxxxxx>
[ Upstream commit 61b6034c6cfdcb265bb453505c3d688e7567727a ]
is_power_of_2 expects unsigned long and we pass u64 max_val_cycles,
this will be truncated on 32 bit systems, and the result is not what we
were expecting.
div_u64 expects u32 as a second argument and we pass
max_val_cycles_rounded which is u64 hence it will always be truncated.
Fix was tested on both 64 and 32 bit systems and got same results for
max_val_cycles and max_val_cycles_rounded.
Fixes: 4850cf458157 ("net/mlx4_en: Resolve dividing by zero in 32-bit system")
Signed-off-by: Slava Shwartsman <slavash@xxxxxxxxxxxx>
Signed-off-by: Tariq Toukan <tariqt@xxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/net/ethernet/mellanox/mlx4/en_clock.c | 8 ++------
1 file changed, 2 insertions(+), 6 deletions(-)
--- a/drivers/net/ethernet/mellanox/mlx4/en_clock.c
+++ b/drivers/net/ethernet/mellanox/mlx4/en_clock.c
@@ -251,13 +251,9 @@ static u32 freq_to_shift(u16 freq)
{
u32 freq_khz = freq * 1000;
u64 max_val_cycles = freq_khz * 1000 * MLX4_EN_WRAP_AROUND_SEC;
- u64 tmp_rounded =
- roundup_pow_of_two(max_val_cycles) > max_val_cycles ?
- roundup_pow_of_two(max_val_cycles) - 1 : UINT_MAX;
- u64 max_val_cycles_rounded = is_power_of_2(max_val_cycles + 1) ?
- max_val_cycles : tmp_rounded;
+ u64 max_val_cycles_rounded = 1ULL << fls64(max_val_cycles - 1);
/* calculate max possible multiplier in order to fit in 64bit */
- u64 max_mul = div_u64(0xffffffffffffffffULL, max_val_cycles_rounded);
+ u64 max_mul = div64_u64(ULLONG_MAX, max_val_cycles_rounded);
/* This comes from the reverse of clocksource_khz2mult */
return ilog2(div_u64(max_mul * freq_khz, 1000000));