e1000e: 82574/82583 TimeSync errata for SYSTIM read

Due to a synchronization error, the value read from SYSTIML/SYSTIMH
might be incorrect.

Signed-off-by: Todd Fujinaka <todd.fujinaka@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

2 files changed, 28 insertions, 1 deletions

diff --git a/drivers/net/ethernet/intel/e1000e/e1000.h b/drivers/net/ethernet/intel/e1000e/e1000.h
index e27e60910949..63bde99a4ab4 100644
--- a/drivers/net/ethernet/intel/e1000e/e1000.h
+++ b/drivers/net/ethernet/intel/e1000e/e1000.h
@@ -391,6 +391,8 @@ s32 e1000e_get_base_timinca(struct e1000_adapter *adapter, u32 *timinca);
  * 25MHz        46-bit  2^46 / 10^9 / 3600 = 19.55 hours
  */
 #define E1000_SYSTIM_OVERFLOW_PERIOD    (HZ * 60 * 60 * 4)
+#define E1000_MAX_82574_SYSTIM_REREADS  50
+#define E1000_82574_SYSTIM_EPSILON      (1ULL << 35ULL)
 
 /* hardware capability, feature, and workaround flags */
 #define FLAG_HAS_AMT                      (1 << 0)
diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c b/drivers/net/ethernet/intel/e1000e/netdev.c
index 6084e6ba45c2..95cf482cf0af 100644
--- a/drivers/net/ethernet/intel/e1000e/netdev.c
+++ b/drivers/net/ethernet/intel/e1000e/netdev.c
@@ -4099,12 +4099,37 @@ 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;
-        cycle_t systim;
+        cycle_t systim, systim_next;
 
         /* latch SYSTIMH on read of SYSTIML */
         systim = (cycle_t)er32(SYSTIML);
         systim |= (cycle_t)er32(SYSTIMH) << 32;
 
+        if ((hw->mac.type == e1000_82574) || (hw->mac.type == e1000_82583)) {
+                u64 incvalue, time_delta, rem, temp;
+                int i;
+
+                /* errata for 82574/82583 possible bad bits read from SYSTIMH/L
+                 * check to see that the time is incrementing at a reasonable
+                 * rate and is a multiple of incvalue
+                 */
+                incvalue = er32(TIMINCA) & E1000_TIMINCA_INCVALUE_MASK;
+                for (i = 0; i < E1000_MAX_82574_SYSTIM_REREADS; i++) {
+                        /* latch SYSTIMH on read of SYSTIML */
+                        systim_next = (cycle_t)er32(SYSTIML);
+                        systim_next |= (cycle_t)er32(SYSTIMH) << 32;
+
+                        time_delta = systim_next - systim;
+                        temp = time_delta;
+                        rem = do_div(temp, incvalue);
+
+                        systim = systim_next;
+
+                        if ((time_delta < E1000_82574_SYSTIM_EPSILON) &&
+                            (rem == 0))
+                                break;
+                }
+        }
         return systim;
 }