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From: Vinicius Costa Gomes <vinicius.gomes@intel.com>
To: intel-wired-lan@lists.osuosl.org
Cc: sasha.neftin@intel.com,
	richardcochran@gmail.com,
	kurt@linutronix.de,
	anthony.l.nguyen@intel.com,
	jesse.brandeburg@intel.com,
	Vinicius Costa Gomes <vinicius.gomes@intel.com>,
	"David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>,
	Paolo Abeni <pabeni@redhat.com>,
	Jeff Kirsher <jeffrey.t.kirsher@intel.com>,
	netdev@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: [iwl-net v1 1/2] igc: Fix missing time sync events
Date: Fri, 16 Feb 2024 17:04:53 -0800
Message-ID: <20240217010455.58258-2-vinicius.gomes@intel.com>
In-Reply-To: <20240217010455.58258-1-vinicius.gomes@intel.com>
References: <20240217010455.58258-1-vinicius.gomes@intel.com>
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Fix "double" clearing of interrupts, which can cause external events
or timestamps to be missed.

The IGC_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 IGC_TSIRC into 'tsicr';
 2. handle the interrupts present in 'tsirc' and mark them in 'ack';
 3. write 'ack' into IGC_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: 2c344ae24501 ("igc: Add support for TX timestamping")
Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
---
 drivers/net/ethernet/intel/igc/igc_main.c | 12 +-----------
 1 file changed, 1 insertion(+), 11 deletions(-)

diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c
index ba8d3fe186ae..39b6a8d64de3 100644
--- a/drivers/net/ethernet/intel/igc/igc_main.c
+++ b/drivers/net/ethernet/intel/igc/igc_main.c
@@ -5302,25 +5302,22 @@ igc_features_check(struct sk_buff *skb, struct net_device *dev,
 
 static void igc_tsync_interrupt(struct igc_adapter *adapter)
 {
-	u32 ack, tsauxc, sec, nsec, tsicr;
 	struct igc_hw *hw = &adapter->hw;
+	u32 tsauxc, sec, nsec, tsicr;
 	struct ptp_clock_event event;
 	struct timespec64 ts;
 
 	tsicr = rd32(IGC_TSICR);
-	ack = 0;
 
 	if (tsicr & IGC_TSICR_SYS_WRAP) {
 		event.type = PTP_CLOCK_PPS;
 		if (adapter->ptp_caps.pps)
 			ptp_clock_event(adapter->ptp_clock, &event);
-		ack |= IGC_TSICR_SYS_WRAP;
 	}
 
 	if (tsicr & IGC_TSICR_TXTS) {
 		/* retrieve hardware timestamp */
 		igc_ptp_tx_tstamp_event(adapter);
-		ack |= IGC_TSICR_TXTS;
 	}
 
 	if (tsicr & IGC_TSICR_TT0) {
@@ -5334,7 +5331,6 @@ static void igc_tsync_interrupt(struct igc_adapter *adapter)
 		wr32(IGC_TSAUXC, tsauxc);
 		adapter->perout[0].start = ts;
 		spin_unlock(&adapter->tmreg_lock);
-		ack |= IGC_TSICR_TT0;
 	}
 
 	if (tsicr & IGC_TSICR_TT1) {
@@ -5348,7 +5344,6 @@ static void igc_tsync_interrupt(struct igc_adapter *adapter)
 		wr32(IGC_TSAUXC, tsauxc);
 		adapter->perout[1].start = ts;
 		spin_unlock(&adapter->tmreg_lock);
-		ack |= IGC_TSICR_TT1;
 	}
 
 	if (tsicr & IGC_TSICR_AUTT0) {
@@ -5358,7 +5353,6 @@ static void igc_tsync_interrupt(struct igc_adapter *adapter)
 		event.index = 0;
 		event.timestamp = sec * NSEC_PER_SEC + nsec;
 		ptp_clock_event(adapter->ptp_clock, &event);
-		ack |= IGC_TSICR_AUTT0;
 	}
 
 	if (tsicr & IGC_TSICR_AUTT1) {
@@ -5368,11 +5362,7 @@ static void igc_tsync_interrupt(struct igc_adapter *adapter)
 		event.index = 1;
 		event.timestamp = sec * NSEC_PER_SEC + nsec;
 		ptp_clock_event(adapter->ptp_clock, &event);
-		ack |= IGC_TSICR_AUTT1;
 	}
-
-	/* acknowledge the interrupts */
-	wr32(IGC_TSICR, ack);
 }
 
 /**
-- 
2.43.2