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path: root/drivers/net/ethernet/mellanox/mlx4/en_clock.c
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Diffstat (limited to 'drivers/net/ethernet/mellanox/mlx4/en_clock.c')
-rw-r--r--drivers/net/ethernet/mellanox/mlx4/en_clock.c25
1 files changed, 19 insertions, 6 deletions
diff --git a/drivers/net/ethernet/mellanox/mlx4/en_clock.c b/drivers/net/ethernet/mellanox/mlx4/en_clock.c
index 038f9ce391e6..1494997c4f7e 100644
--- a/drivers/net/ethernet/mellanox/mlx4/en_clock.c
+++ b/drivers/net/ethernet/mellanox/mlx4/en_clock.c
@@ -236,6 +236,24 @@ static const struct ptp_clock_info mlx4_en_ptp_clock_info = {
.enable = mlx4_en_phc_enable,
};
+#define MLX4_EN_WRAP_AROUND_SEC 10ULL
+
+/* This function calculates the max shift that enables the user range
+ * of MLX4_EN_WRAP_AROUND_SEC values in the cycles register.
+ */
+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 max_val_cycles_rounded = is_power_of_2(max_val_cycles + 1) ?
+ max_val_cycles : roundup_pow_of_two(max_val_cycles) - 1;
+ /* calculate max possible multiplier in order to fit in 64bit */
+ u64 max_mul = div_u64(0xffffffffffffffffULL, max_val_cycles_rounded);
+
+ /* This comes from the reverse of clocksource_khz2mult */
+ return ilog2(div_u64(max_mul * freq_khz, 1000000));
+}
+
void mlx4_en_init_timestamp(struct mlx4_en_dev *mdev)
{
struct mlx4_dev *dev = mdev->dev;
@@ -254,12 +272,7 @@ void mlx4_en_init_timestamp(struct mlx4_en_dev *mdev)
memset(&mdev->cycles, 0, sizeof(mdev->cycles));
mdev->cycles.read = mlx4_en_read_clock;
mdev->cycles.mask = CLOCKSOURCE_MASK(48);
- /* Using shift to make calculation more accurate. Since current HW
- * clock frequency is 427 MHz, and cycles are given using a 48 bits
- * register, the biggest shift when calculating using u64, is 14
- * (max_cycles * multiplier < 2^64)
- */
- mdev->cycles.shift = 14;
+ mdev->cycles.shift = freq_to_shift(dev->caps.hca_core_clock);
mdev->cycles.mult =
clocksource_khz2mult(1000 * dev->caps.hca_core_clock, mdev->cycles.shift);
mdev->nominal_c_mult = mdev->cycles.mult;