[PATCH net-next 02/14] net: mscc: ocelot: make access to STAT_VIEW sleepable again

[Vladimir Oltean]

To support SPI-controlled switches in the future, access to
SYS_STAT_CFG_STAT_VIEW needs to be done outside of any spinlock
protected region, but it still needs to be serialized (by a mutex).

Split the ocelot->stats_lock spinlock into a mutex that serializes
indirect access to hardware registers (ocelot->stat_view_lock) and a
spinlock that serializes access to the u64 ocelot->stats array.

Signed-off-by: Vladimir Oltean <vladimir.oltean@xxxxxxx>
---
 drivers/net/dsa/ocelot/felix_vsc9959.c |  4 +--
 drivers/net/ethernet/mscc/ocelot.c     | 48 ++++++++++++++++++++------
 include/soc/mscc/ocelot.h              |  9 +++--
 3 files changed, 45 insertions(+), 16 deletions(-)

diff --git a/drivers/net/dsa/ocelot/felix_vsc9959.c b/drivers/net/dsa/ocelot/felix_vsc9959.c
index 10db0b69b681..18543bee793b 100644
--- a/drivers/net/dsa/ocelot/felix_vsc9959.c
+++ b/drivers/net/dsa/ocelot/felix_vsc9959.c
@@ -2519,7 +2519,7 @@ static void vsc9959_psfp_sgi_table_del(struct ocelot *ocelot,
 static void vsc9959_psfp_counters_get(struct ocelot *ocelot, u32 index,
 				      struct felix_stream_filter_counters *counters)
 {
-	spin_lock(&ocelot->stats_lock);
+	mutex_lock(&ocelot->stat_view_lock);
 
 	ocelot_rmw(ocelot, SYS_STAT_CFG_STAT_VIEW(index),
 		   SYS_STAT_CFG_STAT_VIEW_M,
@@ -2538,7 +2538,7 @@ static void vsc9959_psfp_counters_get(struct ocelot *ocelot, u32 index,
 		     SYS_STAT_CFG_STAT_CLEAR_SHOT(0x10),
 		     SYS_STAT_CFG);
 
-	spin_unlock(&ocelot->stats_lock);
+	mutex_unlock(&ocelot->stat_view_lock);
 }
 
 static int vsc9959_psfp_filter_add(struct ocelot *ocelot, int port,
diff --git a/drivers/net/ethernet/mscc/ocelot.c b/drivers/net/ethernet/mscc/ocelot.c
index dddaffdaad9a..a677a18239c5 100644
--- a/drivers/net/ethernet/mscc/ocelot.c
+++ b/drivers/net/ethernet/mscc/ocelot.c
@@ -1870,12 +1870,13 @@ void ocelot_get_strings(struct ocelot *ocelot, int port, u32 sset, u8 *data)
 }
 EXPORT_SYMBOL(ocelot_get_strings);
 
-/* Caller must hold &ocelot->stats_lock */
+/* Read the counters from hardware and keep them in region->buf.
+ * Caller must hold &ocelot->stat_view_lock.
+ */
 static int ocelot_port_update_stats(struct ocelot *ocelot, int port)
 {
-	unsigned int idx = port * OCELOT_NUM_STATS;
 	struct ocelot_stats_region *region;
-	int err, j;
+	int err;
 
 	/* Configure the port to read the stats from */
 	ocelot_write(ocelot, SYS_STAT_CFG_STAT_VIEW(port), SYS_STAT_CFG);
@@ -1885,7 +1886,21 @@ static int ocelot_port_update_stats(struct ocelot *ocelot, int port)
 				       region->count);
 		if (err)
 			return err;
+	}
+
+	return 0;
+}
 
+/* Transfer the counters from region->buf to ocelot->stats.
+ * Caller must hold &ocelot->stat_view_lock and &ocelot->stats_lock.
+ */
+static void ocelot_port_transfer_stats(struct ocelot *ocelot, int port)
+{
+	unsigned int idx = port * OCELOT_NUM_STATS;
+	struct ocelot_stats_region *region;
+	int j;
+
+	list_for_each_entry(region, &ocelot->stats_regions, node) {
 		for (j = 0; j < region->count; j++) {
 			u64 *stat = &ocelot->stats[idx + j];
 			u64 val = region->buf[j];
@@ -1898,8 +1913,6 @@ static int ocelot_port_update_stats(struct ocelot *ocelot, int port)
 
 		idx += region->count;
 	}
-
-	return err;
 }
 
 static void ocelot_check_stats_work(struct work_struct *work)
@@ -1907,15 +1920,21 @@ static void ocelot_check_stats_work(struct work_struct *work)
 	struct delayed_work *del_work = to_delayed_work(work);
 	struct ocelot *ocelot = container_of(del_work, struct ocelot,
 					     stats_work);
-	int i, err;
+	int port, err;
 
-	spin_lock(&ocelot->stats_lock);
-	for (i = 0; i < ocelot->num_phys_ports; i++) {
-		err = ocelot_port_update_stats(ocelot, i);
+	mutex_lock(&ocelot->stat_view_lock);
+
+	for (port = 0; port < ocelot->num_phys_ports; port++) {
+		err = ocelot_port_update_stats(ocelot, port);
 		if (err)
 			break;
+
+		spin_lock(&ocelot->stats_lock);
+		ocelot_port_transfer_stats(ocelot, port);
+		spin_unlock(&ocelot->stats_lock);
 	}
-	spin_unlock(&ocelot->stats_lock);
+
+	mutex_unlock(&ocelot->stat_view_lock);
 
 	if (err)
 		dev_err(ocelot->dev, "Error %d updating ethtool stats\n",  err);
@@ -1928,11 +1947,15 @@ void ocelot_get_ethtool_stats(struct ocelot *ocelot, int port, u64 *data)
 {
 	int i, err;
 
-	spin_lock(&ocelot->stats_lock);
+	mutex_lock(&ocelot->stat_view_lock);
 
 	/* check and update now */
 	err = ocelot_port_update_stats(ocelot, port);
 
+	spin_lock(&ocelot->stats_lock);
+
+	ocelot_port_transfer_stats(ocelot, port);
+
 	/* Copy all supported counters */
 	for (i = 0; i < OCELOT_NUM_STATS; i++) {
 		int index = port * OCELOT_NUM_STATS + i;
@@ -1945,6 +1968,8 @@ void ocelot_get_ethtool_stats(struct ocelot *ocelot, int port, u64 *data)
 
 	spin_unlock(&ocelot->stats_lock);
 
+	mutex_unlock(&ocelot->stat_view_lock);
+
 	if (err)
 		dev_err(ocelot->dev, "Error %d updating ethtool stats\n", err);
 }
@@ -3396,6 +3421,7 @@ int ocelot_init(struct ocelot *ocelot)
 		return -ENOMEM;
 
 	spin_lock_init(&ocelot->stats_lock);
+	mutex_init(&ocelot->stat_view_lock);
 	mutex_init(&ocelot->ptp_lock);
 	mutex_init(&ocelot->mact_lock);
 	mutex_init(&ocelot->fwd_domain_lock);
diff --git a/include/soc/mscc/ocelot.h b/include/soc/mscc/ocelot.h
index 99d679235070..e85fb3b15524 100644
--- a/include/soc/mscc/ocelot.h
+++ b/include/soc/mscc/ocelot.h
@@ -901,12 +901,15 @@ struct ocelot {
 
 	struct ocelot_psfp_list		psfp;
 
-	/* Workqueue to check statistics for overflow with its lock */
-	spinlock_t			stats_lock;
-	u64				*stats;
+	/* Workqueue to check statistics for overflow */
 	struct delayed_work		stats_work;
 	struct workqueue_struct		*stats_queue;
+	/* Lock for serializing access to the statistics array */
+	spinlock_t			stats_lock;
+	u64				*stats;
 
+	/* Lock for serializing indirect access to STAT_VIEW registers */
+	struct mutex			stat_view_lock;
 	/* Lock for serializing access to the MAC table */
 	struct mutex			mact_lock;
 	/* Lock for serializing forwarding domain changes */
-- 
2.34.1