Change in osmo-bts[master]: osmo-bts-trx: fix trx_sched_fn(): properly advance frame number

[fixeria]

fixeria has uploaded this change for review. ( https://gerrit.osmocom.org/c/osmo-bts/+/19009 )


Change subject: osmo-bts-trx: fix trx_sched_fn(): properly advance frame number
......................................................................

osmo-bts-trx: fix trx_sched_fn(): properly advance frame number

In trx_sched_fn() we schedule Downlink bursts in advance, in order
to give the transceiver some time to process them.  This function
handles all timeslots of all transceivers in a loop.  The problem
is that the given frame number is overwritten on each iteration.

Let's say we have 4 transceivers, each with default fn-advance 20.
The given frame number N will be advanced 4 times, so the resulting
frame number for 4-th transceiver would be (N + 4 * 20) instead of
(N + 20) as expected.  Therefore, all additional transceivers would
be served more and more in the future (depending on their position).

Change-Id: Ie3ab544eac81a675266df09cd2b7740e4183188e
---
M src/osmo-bts-trx/scheduler_trx.c
1 file changed, 6 insertions(+), 4 deletions(-)



  git pull ssh://gerrit.osmocom.org:29418/osmo-bts refs/changes/09/19009/1

diff --git a/src/osmo-bts-trx/scheduler_trx.c b/src/osmo-bts-trx/scheduler_trx.c
index 3936124..47cc4b5 100644
--- a/src/osmo-bts-trx/scheduler_trx.c
+++ b/src/osmo-bts-trx/scheduler_trx.c
@@ -56,10 +56,11 @@
 }
 
 /* schedule all frames of all TRX for given FN */
-static int trx_sched_fn(struct gsm_bts *bts, uint32_t fn)
+static int trx_sched_fn(struct gsm_bts *bts, const uint32_t fn)
 {
 	struct trx_dl_burst_req br;
 	struct gsm_bts_trx *trx;
+	uint32_t sched_fn;
 	uint8_t tn;
 
 	/* send time indication */
@@ -74,7 +75,7 @@
 
 		/* advance frame number, so the transceiver has more
 		 * time until it must be transmitted. */
-		fn = GSM_TDMA_FN_SUM(fn, plink->u.osmotrx.clock_advance);
+		sched_fn = GSM_TDMA_FN_SUM(fn, plink->u.osmotrx.clock_advance);
 
 		/* we don't schedule, if power is off */
 		if (!trx_if_powered(l1h))
@@ -83,11 +84,12 @@
 		/* process every TS of TRX */
 		for (tn = 0; tn < ARRAY_SIZE(l1t->ts); tn++) {
 			/* ready-to-send */
-			_sched_rts(l1t, tn, GSM_TDMA_FN_SUM(fn, plink->u.osmotrx.rts_advance));
+			_sched_rts(l1t, tn, GSM_TDMA_FN_SUM(sched_fn, plink->u.osmotrx.rts_advance));
 
 			/* All other parameters to be set by _sched_dl_burst() */
 			br = (struct trx_dl_burst_req) {
-				.fn = fn, .tn = tn,
+				.fn = sched_fn,
+				.tn = tn,
 			};
 
 			/* get burst for FN */

-- 
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Gerrit-Project: osmo-bts
Gerrit-Branch: master
Gerrit-Change-Id: Ie3ab544eac81a675266df09cd2b7740e4183188e
Gerrit-Change-Number: 19009
Gerrit-PatchSet: 1
Gerrit-Owner: fixeria <vyanitskiy at sysmocom.de>
Gerrit-MessageType: newchange
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