net: fec: Use a spinlock to guard `fep->ptp_clk_on`

Mutexes cannot be taken in a non-preemptible context,
causing a panic in `fec_ptp_save_state()`. Replacing
`ptp_clk_mutex` by `tmreg_lock` fixes this.

Fixes: 6a4d7234ae9a ("net: fec: ptp: avoid register access when ipg clock is disabled")
Fixes: f79959220fa5 ("fec: Restart PPS after link state change")
Reported-by: Marc Kleine-Budde <mkl@pengutronix.de>
Link: https://lore.kernel.org/all/20220827160922.642zlcd5foopozru@pengutronix.de/
Signed-off-by: Csókás Bence <csokas.bence@prolan.hu>
Tested-by: Francesco Dolcini <francesco.dolcini@toradex.com> # Toradex Apalis iMX6
Link: https://lore.kernel.org/r/20220901140402.64804-1-csokas.bence@prolan.hu
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 10 insertions, 18 deletions

diff --git a/drivers/net/ethernet/freescale/fec_ptp.c b/drivers/net/ethernet/freescale/fec_ptp.c
index c74d04f4b2fd..8dd5a2615a89 100644
--- a/drivers/net/ethernet/freescale/fec_ptp.c
+++ b/drivers/net/ethernet/freescale/fec_ptp.c
@@ -365,21 +365,19 @@ static int fec_ptp_adjtime(struct ptp_clock_info *ptp, s64 delta)
  */
 static int fec_ptp_gettime(struct ptp_clock_info *ptp, struct timespec64 *ts)
 {
-	struct fec_enet_private *adapter =
+	struct fec_enet_private *fep =
 	    container_of(ptp, struct fec_enet_private, ptp_caps);
 	u64 ns;
 	unsigned long flags;
 
-	mutex_lock(&adapter->ptp_clk_mutex);
+	spin_lock_irqsave(&fep->tmreg_lock, flags);
 	/* Check the ptp clock */
-	if (!adapter->ptp_clk_on) {
-		mutex_unlock(&adapter->ptp_clk_mutex);
+	if (!fep->ptp_clk_on) {
+		spin_unlock_irqrestore(&fep->tmreg_lock, flags);
 		return -EINVAL;
 	}
-	spin_lock_irqsave(&adapter->tmreg_lock, flags);
-	ns = timecounter_read(&adapter->tc);
-	spin_unlock_irqrestore(&adapter->tmreg_lock, flags);
-	mutex_unlock(&adapter->ptp_clk_mutex);
+	ns = timecounter_read(&fep->tc);
+	spin_unlock_irqrestore(&fep->tmreg_lock, flags);
 
 	*ts = ns_to_timespec64(ns);
 
@@ -404,10 +402,10 @@ static int fec_ptp_settime(struct ptp_clock_info *ptp,
 	unsigned long flags;
 	u32 counter;
 
-	mutex_lock(&fep->ptp_clk_mutex);
+	spin_lock_irqsave(&fep->tmreg_lock, flags);
 	/* Check the ptp clock */
 	if (!fep->ptp_clk_on) {
-		mutex_unlock(&fep->ptp_clk_mutex);
+		spin_unlock_irqrestore(&fep->tmreg_lock, flags);
 		return -EINVAL;
 	}
 
@@ -417,11 +415,9 @@ static int fec_ptp_settime(struct ptp_clock_info *ptp,
 	 */
 	counter = ns & fep->cc.mask;
 
-	spin_lock_irqsave(&fep->tmreg_lock, flags);
 	writel(counter, fep->hwp + FEC_ATIME);
 	timecounter_init(&fep->tc, &fep->cc, ns);
 	spin_unlock_irqrestore(&fep->tmreg_lock, flags);
-	mutex_unlock(&fep->ptp_clk_mutex);
 	return 0;
 }
 
@@ -518,13 +514,11 @@ static void fec_time_keep(struct work_struct *work)
 	struct fec_enet_private *fep = container_of(dwork, struct fec_enet_private, time_keep);
 	unsigned long flags;
 
-	mutex_lock(&fep->ptp_clk_mutex);
+	spin_lock_irqsave(&fep->tmreg_lock, flags);
 	if (fep->ptp_clk_on) {
-		spin_lock_irqsave(&fep->tmreg_lock, flags);
 		timecounter_read(&fep->tc);
-		spin_unlock_irqrestore(&fep->tmreg_lock, flags);
 	}
-	mutex_unlock(&fep->ptp_clk_mutex);
+	spin_unlock_irqrestore(&fep->tmreg_lock, flags);
 
 	schedule_delayed_work(&fep->time_keep, HZ);
 }
@@ -599,8 +593,6 @@ void fec_ptp_init(struct platform_device *pdev, int irq_idx)
 	}
 	fep->ptp_inc = NSEC_PER_SEC / fep->cycle_speed;
 
-	spin_lock_init(&fep->tmreg_lock);
-
 	fec_ptp_start_cyclecounter(ndev);
 
 	INIT_DELAYED_WORK(&fep->time_keep, fec_time_keep);