[PATCH net-next v5 07/10] net: ethernet: ti: cpts: rework locking

[Grygorii Strashko]

Now spinlock is used to synchronize everything which is not required. Add
mutex and use to sync access to PTP interface and PTP worker and use
spinlock only to sync FIFO/events processing.

Signed-off-by: Grygorii Strashko <grygorii.strashko@xxxxxx>
Acked-by: Richard Cochran <richardcochran@xxxxxxxxx>
---
 drivers/net/ethernet/ti/cpts.c | 53 +++++++++++++++++++---------------
 drivers/net/ethernet/ti/cpts.h |  3 +-
 2 files changed, 32 insertions(+), 24 deletions(-)

diff --git a/drivers/net/ethernet/ti/cpts.c b/drivers/net/ethernet/ti/cpts.c
index 55ba6b425fb5..8db9efdf1708 100644
--- a/drivers/net/ethernet/ti/cpts.c
+++ b/drivers/net/ethernet/ti/cpts.c
@@ -99,9 +99,12 @@ static void cpts_purge_txq(struct cpts *cpts)
  */
 static int cpts_fifo_read(struct cpts *cpts, int match)
 {
+	struct cpts_event *event;
+	unsigned long flags;
 	int i, type = -1;
 	u32 hi, lo;
-	struct cpts_event *event;
+
+	spin_lock_irqsave(&cpts->lock, flags);
 
 	for (i = 0; i < CPTS_FIFO_DEPTH; i++) {
 		if (cpts_fifo_pop(cpts, &hi, &lo))
@@ -109,7 +112,7 @@ static int cpts_fifo_read(struct cpts *cpts, int match)
 
 		if (list_empty(&cpts->pool) && cpts_purge_events(cpts)) {
 			dev_warn(cpts->dev, "cpts: event pool empty\n");
-			return -1;
+			break;
 		}
 
 		event = list_first_entry(&cpts->pool, struct cpts_event, list);
@@ -148,6 +151,9 @@ static int cpts_fifo_read(struct cpts *cpts, int match)
 		if (type == match)
 			break;
 	}
+
+	spin_unlock_irqrestore(&cpts->lock, flags);
+
 	return type == match ? 0 : -1;
 }
 
@@ -161,10 +167,15 @@ static u64 cpts_systim_read(const struct cyclecounter *cc)
 static void cpts_update_cur_time(struct cpts *cpts, int match,
 				 struct ptp_system_timestamp *sts)
 {
+	unsigned long flags;
+
+	/* use spin_lock_irqsave() here as it has to run very fast */
+	spin_lock_irqsave(&cpts->lock, flags);
 	ptp_read_system_prets(sts);
 	cpts_write32(cpts, TS_PUSH, ts_push);
 	cpts_read32(cpts, ts_push);
 	ptp_read_system_postts(sts);
+	spin_unlock_irqrestore(&cpts->lock, flags);
 
 	if (cpts_fifo_read(cpts, match) && match != -1)
 		dev_err(cpts->dev, "cpts: unable to obtain a time stamp\n");
@@ -174,11 +185,10 @@ static void cpts_update_cur_time(struct cpts *cpts, int match,
 
 static int cpts_ptp_adjfreq(struct ptp_clock_info *ptp, s32 ppb)
 {
-	u64 adj;
-	u32 diff, mult;
-	int neg_adj = 0;
-	unsigned long flags;
 	struct cpts *cpts = container_of(ptp, struct cpts, info);
+	int neg_adj = 0;
+	u32 diff, mult;
+	u64 adj;
 
 	if (ppb < 0) {
 		neg_adj = 1;
@@ -189,25 +199,23 @@ static int cpts_ptp_adjfreq(struct ptp_clock_info *ptp, s32 ppb)
 	adj *= ppb;
 	diff = div_u64(adj, 1000000000ULL);
 
-	spin_lock_irqsave(&cpts->lock, flags);
+	mutex_lock(&cpts->ptp_clk_mutex);
 
 	cpts->mult_new = neg_adj ? mult - diff : mult + diff;
 
 	cpts_update_cur_time(cpts, CPTS_EV_PUSH, NULL);
 
-	spin_unlock_irqrestore(&cpts->lock, flags);
-
+	mutex_unlock(&cpts->ptp_clk_mutex);
 	return 0;
 }
 
 static int cpts_ptp_adjtime(struct ptp_clock_info *ptp, s64 delta)
 {
-	unsigned long flags;
 	struct cpts *cpts = container_of(ptp, struct cpts, info);
 
-	spin_lock_irqsave(&cpts->lock, flags);
+	mutex_lock(&cpts->ptp_clk_mutex);
 	timecounter_adjtime(&cpts->tc, delta);
-	spin_unlock_irqrestore(&cpts->lock, flags);
+	mutex_unlock(&cpts->ptp_clk_mutex);
 
 	return 0;
 }
@@ -217,15 +225,14 @@ static int cpts_ptp_gettimeex(struct ptp_clock_info *ptp,
 			      struct ptp_system_timestamp *sts)
 {
 	struct cpts *cpts = container_of(ptp, struct cpts, info);
-	unsigned long flags;
 	u64 ns;
 
-	spin_lock_irqsave(&cpts->lock, flags);
+	mutex_lock(&cpts->ptp_clk_mutex);
 
 	cpts_update_cur_time(cpts, CPTS_EV_PUSH, sts);
 
 	ns = timecounter_read(&cpts->tc);
-	spin_unlock_irqrestore(&cpts->lock, flags);
+	mutex_unlock(&cpts->ptp_clk_mutex);
 
 	*ts = ns_to_timespec64(ns);
 
@@ -235,15 +242,14 @@ static int cpts_ptp_gettimeex(struct ptp_clock_info *ptp,
 static int cpts_ptp_settime(struct ptp_clock_info *ptp,
 			    const struct timespec64 *ts)
 {
-	u64 ns;
-	unsigned long flags;
 	struct cpts *cpts = container_of(ptp, struct cpts, info);
+	u64 ns;
 
 	ns = timespec64_to_ns(ts);
 
-	spin_lock_irqsave(&cpts->lock, flags);
+	mutex_lock(&cpts->ptp_clk_mutex);
 	timecounter_init(&cpts->tc, &cpts->cc, ns);
-	spin_unlock_irqrestore(&cpts->lock, flags);
+	mutex_unlock(&cpts->ptp_clk_mutex);
 
 	return 0;
 }
@@ -339,10 +345,9 @@ static long cpts_overflow_check(struct ptp_clock_info *ptp)
 	unsigned long flags;
 	u64 ns;
 
-	spin_lock_irqsave(&cpts->lock, flags);
-	cpts_update_cur_time(cpts, -1, NULL);
-	spin_unlock_irqrestore(&cpts->lock, flags);
+	mutex_lock(&cpts->ptp_clk_mutex);
 
+	cpts_update_cur_time(cpts, -1, NULL);
 	ns = timecounter_read(&cpts->tc);
 
 	cpts_process_events(cpts);
@@ -356,6 +361,7 @@ static long cpts_overflow_check(struct ptp_clock_info *ptp)
 	spin_unlock_irqrestore(&cpts->txq.lock, flags);
 
 	dev_dbg(cpts->dev, "cpts overflow check at %lld\n", ns);
+	mutex_unlock(&cpts->ptp_clk_mutex);
 	return (long)delay;
 }
 
@@ -425,8 +431,8 @@ static u64 cpts_find_ts(struct cpts *cpts, struct sk_buff *skb,
 	u32 mtype_seqid;
 	u64 ns = 0;
 
-	spin_lock_irqsave(&cpts->lock, flags);
 	cpts_fifo_read(cpts, -1);
+	spin_lock_irqsave(&cpts->lock, flags);
 	list_for_each_safe(this, next, &cpts->events) {
 		event = list_entry(this, struct cpts_event, list);
 		if (event_expired(event)) {
@@ -703,6 +709,7 @@ struct cpts *cpts_create(struct device *dev, void __iomem *regs,
 	cpts->dev = dev;
 	cpts->reg = (struct cpsw_cpts __iomem *)regs;
 	spin_lock_init(&cpts->lock);
+	mutex_init(&cpts->ptp_clk_mutex);
 
 	ret = cpts_of_parse(cpts, node);
 	if (ret)
diff --git a/drivers/net/ethernet/ti/cpts.h b/drivers/net/ethernet/ti/cpts.h
index 421630049ee7..f16e14d67f5f 100644
--- a/drivers/net/ethernet/ti/cpts.h
+++ b/drivers/net/ethernet/ti/cpts.h
@@ -104,7 +104,7 @@ struct cpts {
 	int rx_enable;
 	struct ptp_clock_info info;
 	struct ptp_clock *clock;
-	spinlock_t lock; /* protects time registers */
+	spinlock_t lock; /* protects fifo/events */
 	u32 cc_mult; /* for the nominal frequency */
 	struct cyclecounter cc;
 	struct timecounter tc;
@@ -117,6 +117,7 @@ struct cpts {
 	struct sk_buff_head txq;
 	u64 cur_timestamp;
 	u32 mult_new;
+	struct mutex ptp_clk_mutex; /* sync PTP interface and worker */
 };
 
 void cpts_rx_timestamp(struct cpts *cpts, struct sk_buff *skb);
-- 
2.17.1