[PATCH iwl-net v2 2/5] i40e: serialize timestamp configuration with PTP teardown

From: Xuanqiang Luo <[email protected]>

i40e_remove() can call i40e_ptp_stop() without the networking locks held.
A concurrent hardware timestamp request can observe I40E_FLAG_PTP_ENA
before teardown clears it, then program PRTTSYN_CTL0 after teardown has
disabled the event source. This can leave time sync interrupts enabled
during device removal.

Add ptp_config_lock to serialize the enable check and register programming
in i40e_ptp_hwtstamp_set() with the PTP state transition in
i40e_ptp_stop(). Requests which observe PTP enabled finish programming
before the state transition; later requests return -EOPNOTSUPP and cannot
re-enable the interrupt.

Fixes: 1050713026a0 ("i40e: add support for PTP external synchronization clock")
Signed-off-by: Xuanqiang Luo <[email protected]>
---
 drivers/net/ethernet/intel/i40e/i40e.h      |  2 ++
 drivers/net/ethernet/intel/i40e/i40e_main.c |  1 +
 drivers/net/ethernet/intel/i40e/i40e_ptp.c  | 17 +++++++++++++----
 3 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/intel/i40e/i40e.h b/drivers/net/ethernet/intel/i40e/i40e.h
index 4c8bcaa9dd192..84564d747d09a 100644
--- a/drivers/net/ethernet/intel/i40e/i40e.h
+++ b/drivers/net/ethernet/intel/i40e/i40e.h
@@ -668,6 +668,8 @@ struct i40e_pf {
 	struct timespec64 ptp_prev_hw_time;
 	struct work_struct ptp_extts0_work;
 	ktime_t ptp_reset_start;
+	/* Serializes timestamp configuration with PTP teardown. */
+	struct mutex ptp_config_lock;
 	struct mutex tmreg_lock; /* Used to protect the SYSTIME registers. */
 	u32 ptp_adj_mult;
 	u32 tx_hwtstamp_timeouts;
diff --git a/drivers/net/ethernet/intel/i40e/i40e_main.c b/drivers/net/ethernet/intel/i40e/i40e_main.c
index 0a259351c127e..8c28788ac634f 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_main.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_main.c
@@ -12819,6 +12819,7 @@ static int i40e_sw_init(struct i40e_pf *pf)
 			 "total-port-shutdown was enabled, link-down-on-close is forced on\n");
 	}
 	mutex_init(&pf->switch_mutex);
+	mutex_init(&pf->ptp_config_lock);
 	spin_lock_init(&pf->ptp_tx_lock);
 
 sw_init_done:
diff --git a/drivers/net/ethernet/intel/i40e/i40e_ptp.c b/drivers/net/ethernet/intel/i40e/i40e_ptp.c
index 224568a3af085..f194869947124 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_ptp.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_ptp.c
@@ -1328,17 +1328,23 @@ int i40e_ptp_hwtstamp_set(struct net_device *netdev,
 	struct i40e_pf *pf = np->vsi->back;
 	int err;
 
-	if (!test_bit(I40E_FLAG_PTP_ENA, pf->flags))
-		return -EOPNOTSUPP;
+	mutex_lock(&pf->ptp_config_lock);
+
+	if (!test_bit(I40E_FLAG_PTP_ENA, pf->flags)) {
+		err = -EOPNOTSUPP;
+		goto unlock;
+	}
 
 	err = i40e_ptp_set_timestamp_mode(pf, config);
 	if (err)
-		return err;
+		goto unlock;
 
 	/* save these settings for future reference */
 	pf->tstamp_config = *config;
 
-	return 0;
+unlock:
+	mutex_unlock(&pf->ptp_config_lock);
+	return err;
 }
 
 /**
@@ -1558,6 +1564,8 @@ void i40e_ptp_stop(struct i40e_pf *pf)
 	struct sk_buff *skb;
 	u32 regval;
 
+	mutex_lock(&pf->ptp_config_lock);
+
 	spin_lock_irqsave(&pf->ptp_tx_lock, flags);
 	clear_bit(I40E_FLAG_PTP_ENA, pf->flags);
 	pf->ptp_tx = false;
@@ -1566,6 +1574,7 @@ void i40e_ptp_stop(struct i40e_pf *pf)
 	spin_unlock_irqrestore(&pf->ptp_tx_lock, flags);
 
 	pf->ptp_rx = false;
+	mutex_unlock(&pf->ptp_config_lock);
 
 	if (skb)
 		dev_kfree_skb_any(skb);
-- 
2.43.0