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dyn TS: enhance channel allocator for dynamic TS 

Change _lc_find_bts() to _lc_dyn_find_bts() with added dyn_as_pchan arg to
pass exactly as which pchan we'd like to allocate on a dynamic TS. Add
_lc_find_bts() as wrapper so non-dynamic-TS callers remain unchanged.

Also add dyn_as_pchan arg to _lc_find_trx() (not renaming to dyn and wrapping
because there is only one caller).

Implement dynamic allocator logic in _lc_find_trx() and lchan_alloc().

A returned dynamic channel still needs to be switched to the proper mode, which
will follow in another commit.

Replace a fixme comment with a normal comment in subslots_per_pchan[], because
handling of dynamic TS is now defined.

Change-Id: I18da7679300c43220d9baa6a304e8df74d366249
This commit is contained in:
Neels Hofmeyr 2016-07-14 03:01:24 +02:00
parent f58852d117
commit fdd9ad7c40
1 changed files with 120 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

127
openbsc/src/libbsc/chan_alloc.c
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@ -50,6 +50,13 @@ static int ts_is_usable(struct gsm_bts_trx_ts *ts)
return 0;
}
/* If a dynamic channel is busy changing, it is already taken or not
* yet available. */
if (ts->pchan == GSM_PCHAN_TCH_F_TCH_H_PDCH) {
if (ts->dyn.pchan_is != ts->dyn.pchan_want)
return 0;
}
return 1;
}
@ -72,17 +79,22 @@ static const uint8_t subslots_per_pchan[] = {
[GSM_PCHAN_TCH_F] = 1,
[GSM_PCHAN_TCH_H] = 2,
[GSM_PCHAN_SDCCH8_SACCH8C] = 8,
/* FIXME: what about dynamic TCH_F_TCH_H ? */
[GSM_PCHAN_TCH_F_PDCH] = 1,
[GSM_PCHAN_CCCH_SDCCH4_CBCH] = 4,
[GSM_PCHAN_SDCCH8_SACCH8C_CBCH] = 8,
/*
* GSM_PCHAN_TCH_F_TCH_H_PDCH should not be part of this, those TS are
* handled according to their ts->dyn state.
*/
};
static struct gsm_lchan *
_lc_find_trx(struct gsm_bts_trx *trx, enum gsm_phys_chan_config pchan)
_lc_find_trx(struct gsm_bts_trx *trx, enum gsm_phys_chan_config pchan,
enum gsm_phys_chan_config dyn_as_pchan)
{
struct gsm_bts_trx_ts *ts;
int j, start, stop, dir, ss;
int check_subslots;
if (!trx_is_usable(trx))
return NULL;
@ -105,8 +117,61 @@ _lc_find_trx(struct gsm_bts_trx *trx, enum gsm_phys_chan_config pchan)
continue;
if (ts->pchan != pchan)
continue;
/* check if all sub-slots are allocated yet */
for (ss = 0; ss < subslots_per_pchan[pchan]; ss++) {
/*
* Allocation for fully dynamic timeslots
* (does not apply for ip.access style GSM_PCHAN_TCH_F_PDCH)
*
* Note the special nature of a dynamic timeslot in PDCH mode:
* in PDCH mode, typically, lchan->type is GSM_LCHAN_NONE and
* lchan->state is LCHAN_S_NONE -- an otherwise unused slot
* becomes PDCH implicitly. In the same sense, this channel
* allocator will never be asked to find an available PDCH
* slot; only TCH/F or TCH/H will be requested, and PDCH mode
* means that it is available for switchover.
*
* A dynamic timeslot in PDCH mode may be switched to TCH/F or
* TCH/H. If a dyn TS is already in TCH/F or TCH/H mode, it
* means that it is in use and its mode can't be switched.
*
* The logic concerning channels for TCH/F is trivial: there is
* only one channel, so a dynamic TS in TCH/F mode is already
* taken and not available for allocation. For TCH/H, we need
* to check whether a dynamic timeslot is already in TCH/H mode
* and whether one of the two channels is still available.
*/
if (pchan == GSM_PCHAN_TCH_F_TCH_H_PDCH) {
if (ts->dyn.pchan_is != ts->dyn.pchan_want) {
/* The TS's mode is being switched. Not
* available anymore/yet. */
DEBUGP(DRLL, "%s already in switchover\n",
gsm_ts_and_pchan_name(ts));
continue;
}
if (ts->dyn.pchan_is == GSM_PCHAN_PDCH) {
/* This slot is available. Still check for
* error states to be sure; in all cases the
* first lchan will be used. */
if (ts->lchan->state != LCHAN_S_NONE
&& ts->lchan->state != LCHAN_S_ACTIVE)
continue;
return ts->lchan;
}
if (ts->dyn.pchan_is == dyn_as_pchan) {
/* The requested type matches the dynamic
* timeslot's current mode. A channel may still
* be available (think TCH/H). */
check_subslots = subslots_per_pchan[ts->dyn.pchan_is];
} else
/* Otherwise this slot is not applicable. */
continue;
} else {
/* Not a dynamic channel, there is only one pchan kind: */
check_subslots = subslots_per_pchan[pchan];
}
/* Is a sub-slot still available? */
for (ss = 0; ss < check_subslots; ss++) {
struct gsm_lchan *lc = &ts->lchan[ss];
if (lc->type == GSM_LCHAN_NONE &&
lc->state == LCHAN_S_NONE)
@ -118,20 +183,21 @@ _lc_find_trx(struct gsm_bts_trx *trx, enum gsm_phys_chan_config pchan)
}
static struct gsm_lchan *
_lc_find_bts(struct gsm_bts *bts, enum gsm_phys_chan_config pchan)
_lc_dyn_find_bts(struct gsm_bts *bts, enum gsm_phys_chan_config pchan,
enum gsm_phys_chan_config dyn_as_pchan)
{
struct gsm_bts_trx *trx;
struct gsm_lchan *lc;
if (bts->chan_alloc_reverse) {
llist_for_each_entry_reverse(trx, &bts->trx_list, list) {
lc = _lc_find_trx(trx, pchan);
lc = _lc_find_trx(trx, pchan, dyn_as_pchan);
if (lc)
return lc;
}
} else {
llist_for_each_entry(trx, &bts->trx_list, list) {
lc = _lc_find_trx(trx, pchan);
lc = _lc_find_trx(trx, pchan, dyn_as_pchan);
if (lc)
return lc;
}
@ -140,6 +206,12 @@ _lc_find_bts(struct gsm_bts *bts, enum gsm_phys_chan_config pchan)
return NULL;
}
static struct gsm_lchan *
_lc_find_bts(struct gsm_bts *bts, enum gsm_phys_chan_config pchan)
{
return _lc_dyn_find_bts(bts, pchan, GSM_PCHAN_NONE);
}
/* Allocate a logical channel.
*
* Dynamic channel types: we always prefer a dedicated TS, and only pick +
@ -198,6 +270,18 @@ struct gsm_lchan *lchan_alloc(struct gsm_bts *bts, enum gsm_chan_t type,
if (lchan)
type = GSM_LCHAN_TCH_F;
}
/* try fully dynamic TCH/F_TCH/H_PDCH */
if (lchan == NULL) {
lchan = _lc_dyn_find_bts(bts, GSM_PCHAN_TCH_F_TCH_H_PDCH,
GSM_PCHAN_TCH_H);
if (lchan)
type = GSM_LCHAN_TCH_H;
}
/*
* No need to check fully dynamic channels for TCH/F:
* if no TCH/H was available, neither will be TCH/F.
*/
}
break;
case GSM_LCHAN_TCH_F:
@ -216,6 +300,22 @@ struct gsm_lchan *lchan_alloc(struct gsm_bts *bts, enum gsm_chan_t type,
if (lchan)
type = GSM_LCHAN_TCH_F;
}
/* Try fully dynamic TCH/F_TCH/H_PDCH as TCH/F... */
if (!lchan) {
lchan = _lc_dyn_find_bts(bts,
GSM_PCHAN_TCH_F_TCH_H_PDCH,
GSM_PCHAN_TCH_F);
if (lchan)
type = GSM_LCHAN_TCH_F;
}
/* ...and as TCH/H. */
if (!lchan) {
lchan = _lc_dyn_find_bts(bts,
GSM_PCHAN_TCH_F_TCH_H_PDCH,
GSM_PCHAN_TCH_H);
if (lchan)
type = GSM_LCHAN_TCH_H;
}
break;
case GSM_LCHAN_TCH_H:
lchan =_lc_find_bts(bts, GSM_PCHAN_TCH_H);
@ -225,6 +325,19 @@ struct gsm_lchan *lchan_alloc(struct gsm_bts *bts, enum gsm_chan_t type,
if (lchan)
type = GSM_LCHAN_TCH_F;
}
/* No dedicated TCH/x available -- try fully dynamic
* TCH/F_TCH/H_PDCH */
if (!lchan) {
lchan = _lc_dyn_find_bts(bts,
GSM_PCHAN_TCH_F_TCH_H_PDCH,
GSM_PCHAN_TCH_H);
if (lchan)
type = GSM_LCHAN_TCH_H;
}
/*
* No need to check TCH/F_TCH/H_PDCH channels for TCH/F:
* if no TCH/H was available, neither will be TCH/F.
*/
/* If we don't have TCH/F either, try dynamic TCH/F_PDCH */
if (!lchan) {
lchan = _lc_find_bts(bts, GSM_PCHAN_TCH_F_PDCH);