igc: add support for frame preemption verification

This patch implements the "ethtool --set-mm" callback to trigger the
frame preemption verification handshake.

Uses the MAC Merge Software Verification (mmsv) mechanism in ethtool
to perform the verification handshake for igc.
The structure fpe.mmsv is set by mmsv in ethtool and should remain
read-only for the driver.

Other mmsv callbacks:
a) configure_tx() -> not used yet at this point
   - igc lacks registers to configure FPE in the transmit direction, so
     this API is not utilized for now. When igc supports preemptible queue,
     driver will use this API to manage its configuration.

b) configure_pmac() -> not used
   - this callback dynamically controls pmac_enabled at runtime. For
     example, mmsv calls configure_pmac() and disables pmac_enabled when
     the link partner goes down, even if the user previously enabled it.
     The intention is to save power but it is not feasible in igc
     because it causes an endless adapter reset loop:

   1) Board A and Board B complete the verification handshake. Tx mode
      register for both boards are in TSN mode.
   2) Board B link goes down.

   On Board A:
   3) mmsv calls configure_pmac() with pmac_enabled = false.
   4) configure_pmac() in igc updates a new field based on pmac_enabled.
      Driver uses this field in igc_tsn_new_flags() to indicate that the
      user enabled/disabled FPE.
   5) configure_pmac() in igc calls igc_tsn_offload_apply() to check
      whether an adapter reset is needed. Calls existing logic in
      igc_tsn_will_tx_mode_change() and igc_tsn_new_flags().
   6) Since pmac_enabled is now disabled and no other TSN feature is
      active, igc_tsn_will_tx_mode_change() evaluates to true because Tx
      mode will switch from TSN to Legacy.
   7) Driver resets the adapter.
   8) Registers are set, and Tx mode switches to Legacy.
   9) When link partner is up, steps 3-8 repeat, but this time with
      pmac_enabled = true, reactivating TSN.
      igc_tsn_will_tx_mode_change() evaluates to true again, since Tx
      mode will switch from Legacy to TSN.
  10) Driver resets the adapter.
  11) Adapter reset completes, registers are set, and Tx mode switches to
      TSN.

  On Board B:
  12) Adapter reset on Board A at step 10 causes it to detect its link
      partner as down.
  13) Repeats steps 3-8.
  14) Once reset adapter on Board A is completed at step 11, it detects
      its link partner as up.
  15) Repeats steps 9-11.

   - this cycle repeats indefinitely. To avoid this issue, igc only uses
     mmsv.pmac_enabled to track whether FPE is enabled or disabled.

Co-developed-by: Vinicius Costa Gomes <[email protected]>
Signed-off-by: Vinicius Costa Gomes <[email protected]>
Co-developed-by: Choong Yong Liang <[email protected]>
Signed-off-by: Choong Yong Liang <[email protected]>
Co-developed-by: Chwee-Lin Choong <[email protected]>
Signed-off-by: Chwee-Lin Choong <[email protected]>
Reviewed-by: Vladimir Oltean <[email protected]>
Signed-off-by: Faizal Rahim <[email protected]>
Tested-by: Mor Bar-Gabay <[email protected]>
Signed-off-by: Tony Nguyen <[email protected]>

1 files changed, 1 insertions, 0 deletions

diff --git a/drivers/net/ethernet/intel/igc/igc_base.h b/drivers/net/ethernet/intel/igc/igc_base.h
index bf8cdfbba9ff..6320eabb72fe 100644
--- a/drivers/net/ethernet/intel/igc/igc_base.h
+++ b/drivers/net/ethernet/intel/igc/igc_base.h
@@ -49,6 +49,7 @@ struct igc_adv_tx_context_desc {
 #define IGC_ADVTXD_DCMD_DEXT	0x20000000 /* Descriptor extension (1=Adv) */
 #define IGC_ADVTXD_DCMD_VLE	0x40000000 /* VLAN pkt enable */
 #define IGC_ADVTXD_DCMD_TSE	0x80000000 /* TCP Seg enable */
+#define IGC_ADVTXD_PAYLEN_MASK	0XFFFFC000 /* Adv desc PAYLEN mask */
 #define IGC_ADVTXD_PAYLEN_SHIFT	14 /* Adv desc PAYLEN shift */
 
 #define IGC_RAR_ENTRIES		16