lan966x: Fix sleeping in atomic context

The following warning was seen when we try to connect using ssh to the device.

BUG: sleeping function called from invalid context at kernel/locking/mutex.c:575
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 104, name: dropbear
preempt_count: 1, expected: 0
INFO: lockdep is turned off.
CPU: 0 UID: 0 PID: 104 Comm: dropbear Tainted: G        W           6.18.0-rc2-00399-g6f1ab1b109b9-dirty #530 NONE
Tainted: [W]=WARN
Hardware name: Generic DT based system
Call trace:
 unwind_backtrace from show_stack+0x10/0x14
 show_stack from dump_stack_lvl+0x7c/0xac
 dump_stack_lvl from __might_resched+0x16c/0x2b0
 __might_resched from __mutex_lock+0x64/0xd34
 __mutex_lock from mutex_lock_nested+0x1c/0x24
 mutex_lock_nested from lan966x_stats_get+0x5c/0x558
 lan966x_stats_get from dev_get_stats+0x40/0x43c
 dev_get_stats from dev_seq_printf_stats+0x3c/0x184
 dev_seq_printf_stats from dev_seq_show+0x10/0x30
 dev_seq_show from seq_read_iter+0x350/0x4ec
 seq_read_iter from seq_read+0xfc/0x194
 seq_read from proc_reg_read+0xac/0x100
 proc_reg_read from vfs_read+0xb0/0x2b0
 vfs_read from ksys_read+0x6c/0xec
 ksys_read from ret_fast_syscall+0x0/0x1c
Exception stack(0xf0b11fa8 to 0xf0b11ff0)
1fa0:                   00000001 00001000 00000008 be9048d8 00001000 00000001
1fc0: 00000001 00001000 00000008 00000003 be905920 0000001e 00000000 00000001
1fe0: 0005404c be9048c0 00018684 b6ec2cd8

It seems that we are using a mutex in a atomic context which is wrong.
Change the mutex with a spinlock.

Fixes: 12c2d0a5b8e2 ("net: lan966x: add ethtool configuration and statistics")
Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Link: https://patch.msgid.link/20251105074955.1766792-1-horatiu.vultur@microchip.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

4 files changed, 15 insertions, 17 deletions

diff --git a/drivers/net/ethernet/microchip/lan966x/lan966x_ethtool.c b/drivers/net/ethernet/microchip/lan966x/lan966x_ethtool.c
index 2474dfd330f4..fe4e61405284 100644
--- a/drivers/net/ethernet/microchip/lan966x/lan966x_ethtool.c
+++ b/drivers/net/ethernet/microchip/lan966x/lan966x_ethtool.c
@@ -294,7 +294,7 @@ static void lan966x_stats_update(struct lan966x *lan966x)
 {
 	int i, j;
 
-	mutex_lock(&lan966x->stats_lock);
+	spin_lock(&lan966x->stats_lock);
 
 	for (i = 0; i < lan966x->num_phys_ports; i++) {
 		uint idx = i * lan966x->num_stats;
@@ -310,7 +310,7 @@ static void lan966x_stats_update(struct lan966x *lan966x)
 		}
 	}
 
-	mutex_unlock(&lan966x->stats_lock);
+	spin_unlock(&lan966x->stats_lock);
 }
 
 static int lan966x_get_sset_count(struct net_device *dev, int sset)
@@ -365,7 +365,7 @@ static void lan966x_get_eth_mac_stats(struct net_device *dev,
 
 	idx = port->chip_port * lan966x->num_stats;
 
-	mutex_lock(&lan966x->stats_lock);
+	spin_lock(&lan966x->stats_lock);
 
 	mac_stats->FramesTransmittedOK =
 		lan966x->stats[idx + SYS_COUNT_TX_UC] +
@@ -416,7 +416,7 @@ static void lan966x_get_eth_mac_stats(struct net_device *dev,
 		lan966x->stats[idx + SYS_COUNT_RX_LONG] +
 		lan966x->stats[idx + SYS_COUNT_RX_PMAC_LONG];
 
-	mutex_unlock(&lan966x->stats_lock);
+	spin_unlock(&lan966x->stats_lock);
 }
 
 static const struct ethtool_rmon_hist_range lan966x_rmon_ranges[] = {
@@ -442,7 +442,7 @@ static void lan966x_get_eth_rmon_stats(struct net_device *dev,
 
 	idx = port->chip_port * lan966x->num_stats;
 
-	mutex_lock(&lan966x->stats_lock);
+	spin_lock(&lan966x->stats_lock);
 
 	rmon_stats->undersize_pkts =
 		lan966x->stats[idx + SYS_COUNT_RX_SHORT] +
@@ -500,7 +500,7 @@ static void lan966x_get_eth_rmon_stats(struct net_device *dev,
 		lan966x->stats[idx + SYS_COUNT_TX_SZ_1024_1526] +
 		lan966x->stats[idx + SYS_COUNT_TX_PMAC_SZ_1024_1526];
 
-	mutex_unlock(&lan966x->stats_lock);
+	spin_unlock(&lan966x->stats_lock);
 
 	*ranges = lan966x_rmon_ranges;
 }
@@ -603,7 +603,7 @@ void lan966x_stats_get(struct net_device *dev,
 
 	idx = port->chip_port * lan966x->num_stats;
 
-	mutex_lock(&lan966x->stats_lock);
+	spin_lock(&lan966x->stats_lock);
 
 	stats->rx_bytes = lan966x->stats[idx + SYS_COUNT_RX_OCT] +
 		lan966x->stats[idx + SYS_COUNT_RX_PMAC_OCT];
@@ -685,7 +685,7 @@ void lan966x_stats_get(struct net_device *dev,
 
 	stats->collisions = lan966x->stats[idx + SYS_COUNT_TX_COL];
 
-	mutex_unlock(&lan966x->stats_lock);
+	spin_unlock(&lan966x->stats_lock);
 }
 
 int lan966x_stats_init(struct lan966x *lan966x)
@@ -701,7 +701,7 @@ int lan966x_stats_init(struct lan966x *lan966x)
 		return -ENOMEM;
 
 	/* Init stats worker */
-	mutex_init(&lan966x->stats_lock);
+	spin_lock_init(&lan966x->stats_lock);
 	snprintf(queue_name, sizeof(queue_name), "%s-stats",
 		 dev_name(lan966x->dev));
 	lan966x->stats_queue = create_singlethread_workqueue(queue_name);
diff --git a/drivers/net/ethernet/microchip/lan966x/lan966x_main.c b/drivers/net/ethernet/microchip/lan966x/lan966x_main.c
index 7001584f1b7a..47752d3fde0b 100644
--- a/drivers/net/ethernet/microchip/lan966x/lan966x_main.c
+++ b/drivers/net/ethernet/microchip/lan966x/lan966x_main.c
@@ -1261,7 +1261,6 @@ cleanup_ports:
 
 	cancel_delayed_work_sync(&lan966x->stats_work);
 	destroy_workqueue(lan966x->stats_queue);
-	mutex_destroy(&lan966x->stats_lock);
 
 	debugfs_remove_recursive(lan966x->debugfs_root);
 
@@ -1279,7 +1278,6 @@ static void lan966x_remove(struct platform_device *pdev)
 
 	cancel_delayed_work_sync(&lan966x->stats_work);
 	destroy_workqueue(lan966x->stats_queue);
-	mutex_destroy(&lan966x->stats_lock);
 
 	lan966x_mac_purge_entries(lan966x);
 	lan966x_mdb_deinit(lan966x);
diff --git a/drivers/net/ethernet/microchip/lan966x/lan966x_main.h b/drivers/net/ethernet/microchip/lan966x/lan966x_main.h
index 4f75f0688369..eea286c29474 100644
--- a/drivers/net/ethernet/microchip/lan966x/lan966x_main.h
+++ b/drivers/net/ethernet/microchip/lan966x/lan966x_main.h
@@ -295,8 +295,8 @@ struct lan966x {
 	const struct lan966x_stat_layout *stats_layout;
 	u32 num_stats;
 
-	/* workqueue for reading stats */
-	struct mutex stats_lock;
+	/* lock for reading stats */
+	spinlock_t stats_lock;
 	u64 *stats;
 	struct delayed_work stats_work;
 	struct workqueue_struct *stats_queue;
diff --git a/drivers/net/ethernet/microchip/lan966x/lan966x_vcap_impl.c b/drivers/net/ethernet/microchip/lan966x/lan966x_vcap_impl.c
index a1471e38d118..2a37fc1ba4bc 100644
--- a/drivers/net/ethernet/microchip/lan966x/lan966x_vcap_impl.c
+++ b/drivers/net/ethernet/microchip/lan966x/lan966x_vcap_impl.c
@@ -403,11 +403,11 @@ static void lan966x_es0_read_esdx_counter(struct lan966x *lan966x,
 	u32 counter;
 
 	id = id & 0xff; /* counter limit */
-	mutex_lock(&lan966x->stats_lock);
+	spin_lock(&lan966x->stats_lock);
 	lan_wr(SYS_STAT_CFG_STAT_VIEW_SET(id), lan966x, SYS_STAT_CFG);
 	counter = lan_rd(lan966x, SYS_CNT(LAN966X_STAT_ESDX_GRN_PKTS)) +
 		  lan_rd(lan966x, SYS_CNT(LAN966X_STAT_ESDX_YEL_PKTS));
-	mutex_unlock(&lan966x->stats_lock);
+	spin_unlock(&lan966x->stats_lock);
 	if (counter)
 		admin->cache.counter = counter;
 }
@@ -417,14 +417,14 @@ static void lan966x_es0_write_esdx_counter(struct lan966x *lan966x,
 {
 	id = id & 0xff; /* counter limit */
 
-	mutex_lock(&lan966x->stats_lock);
+	spin_lock(&lan966x->stats_lock);
 	lan_wr(SYS_STAT_CFG_STAT_VIEW_SET(id), lan966x, SYS_STAT_CFG);
 	lan_wr(0, lan966x, SYS_CNT(LAN966X_STAT_ESDX_GRN_BYTES));
 	lan_wr(admin->cache.counter, lan966x,
 	       SYS_CNT(LAN966X_STAT_ESDX_GRN_PKTS));
 	lan_wr(0, lan966x, SYS_CNT(LAN966X_STAT_ESDX_YEL_BYTES));
 	lan_wr(0, lan966x, SYS_CNT(LAN966X_STAT_ESDX_YEL_PKTS));
-	mutex_unlock(&lan966x->stats_lock);
+	spin_unlock(&lan966x->stats_lock);
 }
 
 static void lan966x_vcap_cache_write(struct net_device *dev,