diff options
| -rw-r--r-- | drivers/net/ethernet/intel/e1000e/netdev.c | 31 |
1 files changed, 21 insertions, 10 deletions
diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c b/drivers/net/ethernet/intel/e1000e/netdev.c index 24b7269ff929..96a816683698 100644 --- a/drivers/net/ethernet/intel/e1000e/netdev.c +++ b/drivers/net/ethernet/intel/e1000e/netdev.c @@ -4280,18 +4280,29 @@ static cycle_t e1000e_cyclecounter_read(const struct cyclecounter *cc) struct e1000_adapter *adapter = container_of(cc, struct e1000_adapter, cc); struct e1000_hw *hw = &adapter->hw; + u32 systimel_1, systimel_2, systimeh; cycle_t systim, systim_next; - /* SYSTIMH latching upon SYSTIML read does not work well. To fix that - * we don't want to allow overflow of SYSTIML and a change to SYSTIMH - * to occur between reads, so if we read a vale close to overflow, we - * wait for overflow to occur and read both registers when its safe. + /* SYSTIMH latching upon SYSTIML read does not work well. + * This means that if SYSTIML overflows after we read it but before + * we read SYSTIMH, the value of SYSTIMH has been incremented and we + * will experience a huge non linear increment in the systime value + * to fix that we test for overflow and if true, we re-read systime. */ - u32 systim_overflow_latch_fix = 0x3FFFFFFF; - - do { - systim = (cycle_t)er32(SYSTIML); - } while (systim > systim_overflow_latch_fix); - systim |= (cycle_t)er32(SYSTIMH) << 32; + systimel_1 = er32(SYSTIML); + systimeh = er32(SYSTIMH); + systimel_2 = er32(SYSTIML); + /* Check for overflow. If there was no overflow, use the values */ + if (systimel_1 < systimel_2) { + systim = (cycle_t)systimel_1; + systim |= (cycle_t)systimeh << 32; + } else { + /* There was an overflow, read again SYSTIMH, and use + * systimel_2 + */ + systimeh = er32(SYSTIMH); + systim = (cycle_t)systimel_2; + systim |= (cycle_t)systimeh << 32; + } if ((hw->mac.type == e1000_82574) || (hw->mac.type == e1000_82583)) { u64 incvalue, time_delta, rem, temp; |