[PATCH v3 net 4/4] net/sched: taprio: get corrected value of cycle_time and interval

[Faizal Rahim]

Added a new field, correction_active to determine the entry's correction
state. This field is required due to specific flow like
find_entry_to_transmit() -> get_interval_end_time() which retrieves
the interval for each entry. During positive cycle time correction,
it's known that the last entry interval requires correction.
However, for negative correction, the affected entry is unknown, which
is why this new field is necessary.

Note that in some cases where the original values are required,
such as in dump_schedule() and setup_first_end_time(), direct calls
to cycle_time and interval are retained without using the new functions.

Signed-off-by: Faizal Rahim <faizal.abdul.rahim@xxxxxxxxxxxxxxx>
---
 net/sched/sch_taprio.c | 34 ++++++++++++++++++++++++++++------
 1 file changed, 28 insertions(+), 6 deletions(-)

diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c
index a3c71be21af2..d11ddb1f554c 100644
--- a/net/sched/sch_taprio.c
+++ b/net/sched/sch_taprio.c
@@ -61,6 +61,7 @@ struct sched_entry {
 	u32 gate_mask;
 	u32 interval;
 	u8 command;
+	bool correction_active;
 };
 
 struct sched_gate_list {
@@ -220,6 +221,14 @@ static bool sched_switch_pending(const struct sched_gate_list *oper)
 	return oper->cycle_time_correction != CYCLE_TIME_CORRECTION_UNSPEC;
 }
 
+static s64 get_cycle_time(const struct sched_gate_list *oper)
+{
+	if (sched_switch_pending(oper))
+		return oper->cycle_time + oper->cycle_time_correction;
+	else
+		return oper->cycle_time;
+}
+
 /* Get how much time has been already elapsed in the current cycle. */
 static s32 get_cycle_time_elapsed(struct sched_gate_list *sched, ktime_t time)
 {
@@ -227,11 +236,20 @@ static s32 get_cycle_time_elapsed(struct sched_gate_list *sched, ktime_t time)
 	s32 time_elapsed;
 
 	time_since_sched_start = ktime_sub(time, sched->base_time);
-	div_s64_rem(time_since_sched_start, sched->cycle_time, &time_elapsed);
+	div_s64_rem(time_since_sched_start, get_cycle_time(sched), &time_elapsed);
 
 	return time_elapsed;
 }
 
+static u32 get_interval(const struct sched_entry *entry,
+			const struct sched_gate_list *oper)
+{
+	if (entry->correction_active)
+		return entry->interval + oper->cycle_time_correction;
+	else
+		return entry->interval;
+}
+
 static ktime_t get_interval_end_time(struct sched_gate_list *sched,
 				     struct sched_gate_list *admin,
 				     struct sched_entry *entry,
@@ -240,8 +258,9 @@ static ktime_t get_interval_end_time(struct sched_gate_list *sched,
 	s32 cycle_elapsed = get_cycle_time_elapsed(sched, intv_start);
 	ktime_t intv_end, cycle_ext_end, cycle_end;
 
-	cycle_end = ktime_add_ns(intv_start, sched->cycle_time - cycle_elapsed);
-	intv_end = ktime_add_ns(intv_start, entry->interval);
+	cycle_end = ktime_add_ns(intv_start,
+				 get_cycle_time(sched) - cycle_elapsed);
+	intv_end = ktime_add_ns(intv_start, get_interval(entry, sched));
 	cycle_ext_end = ktime_add(cycle_end, sched->cycle_time_extension);
 
 	if (ktime_before(intv_end, cycle_end))
@@ -348,7 +367,7 @@ static struct sched_entry *find_entry_to_transmit(struct sk_buff *skb,
 	if (!sched)
 		return NULL;
 
-	cycle = sched->cycle_time;
+	cycle = get_cycle_time(sched);
 	cycle_elapsed = get_cycle_time_elapsed(sched, time);
 	curr_intv_end = ktime_sub_ns(time, cycle_elapsed);
 	cycle_end = ktime_add_ns(curr_intv_end, cycle);
@@ -362,7 +381,7 @@ static struct sched_entry *find_entry_to_transmit(struct sk_buff *skb,
 			break;
 
 		if (!(entry->gate_mask & BIT(tc)) ||
-		    packet_transmit_time > entry->interval)
+		    packet_transmit_time > get_interval(entry, sched))
 			continue;
 
 		txtime = entry->next_txtime;
@@ -540,7 +559,8 @@ static long get_packet_txtime(struct sk_buff *skb, struct Qdisc *sch)
 		 * interval starts.
 		 */
 		if (ktime_after(transmit_end_time, interval_end))
-			entry->next_txtime = ktime_add(interval_start, sched->cycle_time);
+			entry->next_txtime =
+				ktime_add(interval_start, get_cycle_time(sched));
 	} while (sched_changed || ktime_after(transmit_end_time, interval_end));
 
 	entry->next_txtime = transmit_end_time;
@@ -1033,6 +1053,7 @@ static enum hrtimer_restart advance_sched(struct hrtimer *timer)
 
 			oper->cycle_end_time = new_base_time;
 			end_time = new_base_time;
+			next->correction_active = true;
 
 			update_open_gate_duration(next, oper, num_tc,
 						  new_gate_duration);
@@ -1133,6 +1154,7 @@ static int fill_sched_entry(struct taprio_sched *q, struct nlattr **tb,
 	}
 
 	entry->interval = interval;
+	entry->correction_active = false;
 
 	return 0;
 }
-- 
2.25.1