[iwl-net v1 2/2] igb: Fix missing time sync events

[Vinicius Costa Gomes]

Fix "double" clearing of interrupts, which can cause external events
or timestamps to be missed.

The E1000_TSIRC Time Sync Interrupt Cause register can be cleared in two
ways, by either reading it or by writing '1' into the specific cause
bit. This is documented in section 8.16.1.

The following flow was used:
    1. read E1000_TSIRC into 'tsicr';
    2. handle the interrupts present into 'tsirc' and mark them in 'ack';
    3. write 'ack' into E1000_TSICR;

As both (1) and (3) will clear the interrupt cause, if an interrupt
happens between (1) and (3) it will be ignored, causing events to be
missed.

Remove the extra clear in (3).

Fixes: 00c65578b47b ("igb: enable internal PPS for the i210")
Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@xxxxxxxxx>
---
 drivers/net/ethernet/intel/igb/igb_main.c | 23 +++++------------------
 1 file changed, 5 insertions(+), 18 deletions(-)

diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
index cebb44f51d5f..7662c42e35c1 100644
--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -6985,44 +6985,31 @@ static void igb_extts(struct igb_adapter *adapter, int tsintr_tt)
 static void igb_tsync_interrupt(struct igb_adapter *adapter)
 {
 	struct e1000_hw *hw = &adapter->hw;
-	u32 ack = 0, tsicr = rd32(E1000_TSICR);
+	u32 tsicr = rd32(E1000_TSICR);
 	struct ptp_clock_event event;
 
 	if (tsicr & TSINTR_SYS_WRAP) {
 		event.type = PTP_CLOCK_PPS;
 		if (adapter->ptp_caps.pps)
 			ptp_clock_event(adapter->ptp_clock, &event);
-		ack |= TSINTR_SYS_WRAP;
 	}
 
 	if (tsicr & E1000_TSICR_TXTS) {
 		/* retrieve hardware timestamp */
 		schedule_work(&adapter->ptp_tx_work);
-		ack |= E1000_TSICR_TXTS;
 	}
 
-	if (tsicr & TSINTR_TT0) {
+	if (tsicr & TSINTR_TT0)
 		igb_perout(adapter, 0);
-		ack |= TSINTR_TT0;
-	}
 
-	if (tsicr & TSINTR_TT1) {
+	if (tsicr & TSINTR_TT1)
 		igb_perout(adapter, 1);
-		ack |= TSINTR_TT1;
-	}
 
-	if (tsicr & TSINTR_AUTT0) {
+	if (tsicr & TSINTR_AUTT0)
 		igb_extts(adapter, 0);
-		ack |= TSINTR_AUTT0;
-	}
 
-	if (tsicr & TSINTR_AUTT1) {
+	if (tsicr & TSINTR_AUTT1)
 		igb_extts(adapter, 1);
-		ack |= TSINTR_AUTT1;
-	}
-
-	/* acknowledge the interrupts */
-	wr32(E1000_TSICR, ack);
 }
 
 static irqreturn_t igb_msix_other(int irq, void *data)
-- 
2.43.2