From: Denys Vlasenko <dvlas...@redhat.com>
If two consecutive reads of the counter are the same, it is also
not an overflow. "systimel_1 < systimel_2" should be
"systimel_1 <= systimel_2".
Before the patch, we could perform an *erroneous* correction:
Let's say that systimel_1 == systimel_2 == 0xffffffff.
"systimel_1 < systimel_2" is false, we think it's an overflow,
we read "systimeh = er32(SYSTIMH)" which meanwhile had incremented,
and use "(systimeh << 32) + systimel_2" value which is 2^32 too large.
Signed-off-by: Denys Vlasenko <dvlas...@redhat.com>
CC: intel-wired-...@lists.osuosl.org
Tested-by: Aaron Brown <aaron.f.br...@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirs...@intel.com>
---
drivers/net/ethernet/intel/e1000e/netdev.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c
b/drivers/net/ethernet/intel/e1000e/netdev.c
index 4969f64..02c64bc 100644
--- a/drivers/net/ethernet/intel/e1000e/netdev.c
+++ b/drivers/net/ethernet/intel/e1000e/netdev.c
@@ -4287,7 +4287,7 @@ static cycle_t e1000e_cyclecounter_read(const struct
cyclecounter *cc)
systimeh = er32(SYSTIMH);
systimel_2 = er32(SYSTIML);
/* Check for overflow. If there was no overflow, use the values */
- if (systimel_1 < systimel_2) {
+ if (systimel_1 <= systimel_2) {
systim = (cycle_t)systimel_1;
systim |= (cycle_t)systimeh << 32;
} else {
--
2.5.5
