Review at https://gerrit.osmocom.org/6697
host/trxcon/scheduler: implement SCH decoding
Change-Id: Ic5e7416271d647752cd1aaf90de51fa48286798e
---
M src/host/trxcon/sched_lchan_desc.c
M src/host/trxcon/sched_lchan_handlers.c
2 files changed, 73 insertions(+), 2 deletions(-)
git pull ssh://gerrit.osmocom.org:29418/osmocom-bb refs/changes/97/6697/1
diff --git a/src/host/trxcon/sched_lchan_desc.c
b/src/host/trxcon/sched_lchan_desc.c
index 93927a6..1ff6e14 100644
--- a/src/host/trxcon/sched_lchan_desc.c
+++ b/src/host/trxcon/sched_lchan_desc.c
@@ -44,6 +44,10 @@
uint32_t fn, enum trx_lchan_type chan, uint8_t bid,
sbit_t *bits, uint16_t nbits, int8_t rssi, float toa);
+int rx_sch_fn(struct trx_instance *trx, struct trx_ts *ts,
+ uint32_t fn, enum trx_lchan_type chan, uint8_t bid,
+ sbit_t *bits, uint16_t nbits, int8_t rssi, float toa);
+
const struct trx_lchan_desc trx_lchan_desc[_TRX_CHAN_MAX] = {
{
TRXC_IDLE, "IDLE",
@@ -69,8 +73,11 @@
0x00, LID_DEDIC,
0x00, 0x00,
- /* We already have clock indications from TRX */
- NULL, NULL,
+ /**
+ * We already have clock indications from TRX,
+ * but we also need BSIC (BCC / NCC) value.
+ */
+ rx_sch_fn, NULL,
},
{
TRXC_BCCH, "BCCH",
diff --git a/src/host/trxcon/sched_lchan_handlers.c
b/src/host/trxcon/sched_lchan_handlers.c
index 2c2cb6a..41e60d8 100644
--- a/src/host/trxcon/sched_lchan_handlers.c
+++ b/src/host/trxcon/sched_lchan_handlers.c
@@ -34,6 +34,7 @@
#include <osmocom/core/msgb.h>
#include <osmocom/core/fsm.h>
+#include <osmocom/gsm/gsm_utils.h>
#include <osmocom/coding/gsm0503_coding.h>
#include "l1ctl_proto.h"
@@ -159,3 +160,66 @@
/* TODO: AGC, TA loops */
return 0;
}
+
+static void decode_sb(struct gsm_time *time, uint8_t *bsic, uint8_t *sb_info)
+{
+ uint8_t t3p;
+ uint32_t sb;
+
+ sb = (sb_info[3] << 24)
+ | (sb_info[2] << 16)
+ | (sb_info[1] << 8)
+ | sb_info[0];
+
+ *bsic = (sb >> 2) & 0x3f;
+
+ /* TS 05.02 Chapter 3.3.2.2.1 SCH Frame Numbers */
+ time->t1 = ((sb >> 23) & 0x01)
+ | ((sb >> 7) & 0x1fe)
+ | ((sb << 9) & 0x600);
+
+ time->t2 = (sb >> 18) & 0x1f;
+
+ t3p = ((sb >> 24) & 0x01) | ((sb >> 15) & 0x06);
+ time->t3 = t3p * 10 + 1;
+
+ /* TS 05.02 Chapter 4.3.3 TDMA frame number */
+ time->fn = gsm_gsmtime2fn(time);
+}
+
+int rx_sch_fn(struct trx_instance *trx, struct trx_ts *ts,
+ uint32_t fn, enum trx_lchan_type chan, uint8_t bid,
+ sbit_t *bits, uint16_t nbits, int8_t rssi, float toa)
+{
+ sbit_t payload[2 * 39];
+ struct gsm_time time;
+ uint8_t sb_info[4];
+ uint8_t bsic;
+ int rc;
+
+ /* Obtain payload from burst */
+ memcpy(payload, bits + 3, 39);
+ memcpy(payload + 39, bits + 3 + 39 + 64, 39);
+
+ /* Attempt to decode */
+ rc = gsm0503_sch_decode(sb_info, payload);
+ if (rc) {
+ LOGP(DSCH, LOGL_DEBUG, "Received bad SCH burst at fn=%u\n", fn);
+ return rc;
+ }
+
+ /* Decode BSIC and TDMA frame number */
+ decode_sb(&time, &bsic, sb_info);
+
+ LOGP(DSCH, LOGL_DEBUG, "Received SCH: bsic=%u, fn=%u, sched_fn=%u\n",
+ bsic, time.fn, trx->sched.fn_counter_proc);
+
+ /* Check if decoded frame number matches */
+ if (time.fn != fn) {
+ LOGP(DSCH, LOGL_ERROR, "Decoded fn=%u does not match "
+ "fn=%u provided by scheduler\n", time.fn, fn);
+ return -EINVAL;
+ }
+
+ return 0;
+}
--
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Gerrit-MessageType: newchange
Gerrit-Change-Id: Ic5e7416271d647752cd1aaf90de51fa48286798e
Gerrit-PatchSet: 1
Gerrit-Project: osmocom-bb
Gerrit-Branch: master
Gerrit-Owner: Harald Welte <lafo...@gnumonks.org>
