[PATCH net v3] net: macb: initialize PTP state before registering clock

[Runyu Xiao <runyu.xiao@seu.edu.cn>]

gem_ptp_init() registers the PTP clock before initializing
bp->tsu_clk_lock and the TSU hardware. Since ptp_clock_register()
publishes the PTP character device, userspace may invoke PTP callbacks
before the lock and hardware are ready.

In addition, gem_ptp_init() is called from both the interface open and
resume paths. Reinitializing tsu_clk_lock there can reset the lock while
timestamp processing is using it.

This race is theoretical and has not been observed in practice.

Initialize tsu_clk_lock once during probe and initialize the TSU before
registering the PTP clock.

Fixes: ab91f0a9b5f4 ("net: macb: Add hardware PTP support")
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/netdev/20260904030439.3994047-1-runyu.xiao@seu.edu.cn/
Assisted-by: LLM Codex
Reviewed-by: Théo Lebrun <theo.lebrun@bootlin.com>
Reviewed-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
Signed-off-by: Runyu Xiao <runyu.xiao@seu.edu.cn>

---
v3:
- State that the race is theoretical and has not been observed in practice.
- Add Reviewed-by trailers from Théo Lebrun and Vadim Fedorenko.
- Use the documented Assisted-by format.
 drivers/net/ethernet/cadence/macb_main.c | 1 +
 drivers/net/ethernet/cadence/macb_ptp.c  | 6 +-----
 2 files changed, 2 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
index daa8a4a14..76d38415f 100644
--- a/drivers/net/ethernet/cadence/macb_main.c
+++ b/drivers/net/ethernet/cadence/macb_main.c
@@ -5881,6 +5881,7 @@ static int macb_probe(struct platform_device *pdev)
 	}
 	spin_lock_init(&bp->lock);
 	spin_lock_init(&bp->stats_lock);
+	spin_lock_init(&bp->tsu_clk_lock);
 
 	/* setup capabilities */
 	macb_configure_caps(bp, macb_config);
diff --git a/drivers/net/ethernet/cadence/macb_ptp.c b/drivers/net/ethernet/cadence/macb_ptp.c
index e5195d7da..e9c9c2692 100644
--- a/drivers/net/ethernet/cadence/macb_ptp.c
+++ b/drivers/net/ethernet/cadence/macb_ptp.c
@@ -334,6 +334,7 @@ void gem_ptp_init(struct net_device *netdev)
 	bp->tsu_rate = bp->ptp_info->get_tsu_rate(bp);
 	bp->ptp_clock_info.max_adj = bp->ptp_info->get_ptp_max_adj();
 	gem_ptp_init_timer(bp);
+	gem_ptp_init_tsu(bp);
 	bp->ptp_clock = ptp_clock_register(&bp->ptp_clock_info, &netdev->dev);
 	if (IS_ERR(bp->ptp_clock)) {
 		pr_err("ptp clock register failed: %ld\n",
@@ -345,10 +346,6 @@ void gem_ptp_init(struct net_device *netdev)
 		return;
 	}
 
-	spin_lock_init(&bp->tsu_clk_lock);
-
-	gem_ptp_init_tsu(bp);
-
 	dev_info(&bp->pdev->dev, "%s ptp clock registered.\n",
 		 GEM_PTP_TIMER_NAME);
 }
@@ -467,4 +464,3 @@ int gem_set_hwtst(struct net_device *netdev,
 
 	return 0;
 }
-