On 2/26/2017 11:08, Neftin, Sasha wrote:

On 2/19/2017 14:55, Neftin, Sasha wrote:

quoted

On 2/16/2017 20:42, Bernd Faust wrote:

quoted

After an upgrade to Linux kernel v4.x the hardware timestamps of the
82579 Gigabit Ethernet Controller are different than expected.
The values that are being read are almost four times as big as before
the kernel upgrade.

The difference is that after the upgrade the driver sets the clock
frequency to 25MHz, where before the upgrade it was set to 96MHz. Intel
confirmed that the correct frequency for this network adapter is 96MHz.

Signed-off-by: Bernd Faust <redacted>
---
  drivers/net/ethernet/intel/e1000e/netdev.c | 6 ++++++
  1 file changed, 6 insertions(+)

diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c 

b/drivers/net/ethernet/intel/e1000e/netdev.c
index 7017281..8b7113d 100644

--- a/drivers/net/ethernet/intel/e1000e/netdev.c
+++ b/drivers/net/ethernet/intel/e1000e/netdev.c

@@ -3511,6 +3511,12 @@ s32 e1000e_get_base_timinca(struct 

e1000_adapter *adapter, u32 *timinca)

      switch (hw->mac.type) {
      case e1000_pch2lan:
+        /* Stable 96MHz frequency */
+        incperiod = INCPERIOD_96MHz;
+        incvalue = INCVALUE_96MHz;
+        shift = INCVALUE_SHIFT_96MHz;
+        adapter->cc.shift = shift + INCPERIOD_SHIFT_96MHz;
+        break;
      case e1000_pch_lpt:
          if (er32(TSYNCRXCTL) & E1000_TSYNCRXCTL_SYSCFI) {
              /* Stable 96MHz frequency */
-- 
2.7.4
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Hello,

e1000_pch2lan mac type corresponds to 82579LM and 82579V network 
adapters. System clock frequency indication (SYSCFI) for these 
devices supports both 25MHz and 96MHz frequency. By default 
TSYNCRXCTL.SYSCFI is set to 1 and that means 96MHz frequency is picked.

It is better to keep the current implementation as it covers all 
options.

Thanks,

Sasha

Hello,

During last couple of weeks I saw few  complaints from community on 
same timing problem with 82579. I will double check clock definition 
with HW architecture.

Sasha

I've double checked - 82579 support 96MHz frequency only. So, let's 
accept this suggestion to upstream.

Ack.