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Bluetooth: Controller: Added comments for CSA #2 implementation

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Added Bluetooth Specification references to the
implementation of Channel Selection algorithm #2 in the
Controller.

Signed-off-by: Vinayak Kariappa Chettimada <vich@nordicsemi.no>
This commit is contained in:
Vinayak Kariappa Chettimada 2021-06-29 16:51:33 +05:30 committed by Carles Cufí
parent 7b12723aad
commit ba6be70129
1 changed files with 61 additions and 0 deletions
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61
subsys/bluetooth/controller/ll_sw/lll_chan.c
View file

@ -29,6 +29,9 @@ static uint8_t chan_d(uint8_t n);
#endif /* CONFIG_BT_CTLR_CHAN_SEL_2 */
#if defined(CONFIG_BT_CONN)
/* Refer to Bluetooth Specification v5.2 Vol 6, Part B, Section 4.5.8.2
* Channel Selection algorithm #1
*/
uint8_t lll_chan_sel_1(uint8_t *chan_use, uint8_t hop, uint16_t latency, uint8_t *chan_map,
uint8_t chan_count)
{
@ -52,6 +55,9 @@ uint8_t lll_chan_sel_1(uint8_t *chan_use, uint8_t hop, uint16_t latency, uint8_t
#endif /* CONFIG_BT_CONN */
#if defined(CONFIG_BT_CTLR_CHAN_SEL_2)
/* Refer to Bluetooth Specification v5.2 Vol 6, Part B, Section 4.5.8.3.2
* Inputs and basic components
*/
uint16_t lll_chan_id(uint8_t *access_addr)
{
uint16_t aa_ls = ((uint16_t)access_addr[1] << 8) | access_addr[0];
@ -60,6 +66,10 @@ uint16_t lll_chan_id(uint8_t *access_addr)
return aa_ms ^ aa_ls;
}
/* Refer to Bluetooth Specification v5.2 Vol 6, Part B, Section 4.5.8.3
* Channel Selection algorithm #2, and Section 4.5.8.3.1 Overview
* Below interface is used for ACL connections.
*/
uint8_t lll_chan_sel_2(uint16_t counter, uint16_t chan_id, uint8_t *chan_map,
uint8_t chan_count)
{
@ -83,6 +93,11 @@ uint8_t lll_chan_sel_2(uint16_t counter, uint16_t chan_id, uint8_t *chan_map,
}
#if defined(CONFIG_BT_CTLR_ADV_ISO) || defined(CONFIG_BT_CTLR_SYNC_ISO)
/* Refer to Bluetooth Specification v5.2 Vol 6, Part B, Section 4.5.8.3
* Channel Selection algorithm #2, and Section 4.5.8.3.1 Overview
*
* Below interface is used for ISO first subevent.
*/
uint8_t lll_chan_iso_event(uint16_t counter, uint16_t chan_id,
uint8_t *chan_map, uint8_t chan_count,
uint16_t *prn_s, uint16_t *remap_idx)
@ -105,6 +120,11 @@ uint8_t lll_chan_iso_event(uint16_t counter, uint16_t chan_id,
return chan_idx;
}
/* Refer to Bluetooth Specification v5.2 Vol 6, Part B, Section 4.5.8.3
* Channel Selection algorithm #2, and Section 4.5.8.3.1 Overview
*
* Below interface is used for ISO next subevent.
*/
uint8_t lll_chan_iso_subevent(uint16_t chan_id, uint8_t *chan_map,
uint8_t chan_count, uint16_t *prn_subevent_lu,
uint16_t *remap_idx)
@ -117,6 +137,10 @@ uint8_t lll_chan_iso_subevent(uint16_t chan_id, uint8_t *chan_map,
prn_subevent_se = chan_prn_subevent_se(chan_id, prn_subevent_lu);
d = chan_d(chan_count);
/* Sub-expression to get natural number (N - 2d + 1) to be used in the
* calculation of d.
*/
if ((chan_count + 1) > (d << 1)) {
x = (chan_count + 1) - (d << 1);
} else {
@ -138,6 +162,10 @@ uint8_t lll_chan_iso_subevent(uint16_t chan_id, uint8_t *chan_map,
#endif /* CONFIG_BT_CTLR_ADV_ISO || CONFIG_BT_CTLR_SYNC_ISO */
#endif /* CONFIG_BT_CTLR_CHAN_SEL_2 */
/* Refer to Bluetooth Specification v5.2 Vol 6, Part B, Section 4.5.8.3
* Channel Selection algorithm #2, and Section 4.5.8.3.4 Event mapping to used
* channel index
*/
static uint8_t chan_sel_remap(uint8_t *chan_map, uint8_t chan_index)
{
uint8_t chan_next;
@ -176,6 +204,9 @@ static uint8_t chan_sel_remap(uint8_t *chan_map, uint8_t chan_index)
/* Attribution:
* http://graphics.stanford.edu/%7Eseander/bithacks.html#ReverseByteWith32Bits
*/
/* Refer to Bluetooth Specification v5.2 Vol 6, Part B, Section 4.5.8.3.2
* Inputs and basic components, for below operations
*/
static uint8_t chan_rev_8(uint8_t b)
{
b = (((uint32_t)b * 0x0802LU & 0x22110LU) |
@ -220,6 +251,13 @@ static uint16_t chan_prn_e(uint16_t counter, uint16_t chan_id)
}
#if defined(CONFIG_BT_CTLR_ADV_ISO) || defined(CONFIG_BT_CTLR_SYNC_ISO)
/* Refer to Bluetooth Specification v5.2 Vol 6, Part B, Section 4.5.8.3
* Channel Selection algorithm #2, and Section 4.5.8.3.4 Event mapping to used
* channel index
*
* Below function is used in the context of next subevent, return remapping
* index.
*/
static uint8_t chan_sel_remap_index(uint8_t *chan_map, uint8_t chan_index)
{
uint8_t octet_count;
@ -251,6 +289,10 @@ static uint8_t chan_sel_remap_index(uint8_t *chan_map, uint8_t chan_index)
return 0;
}
/* Refer to Bluetooth Specification v5.2 Vol 6, Part B, Section 4.5.8.3
* Channel Selection algorithm #2, and Section 4.5.8.3.5 Subevent pseudo-random
* number generation
*/
static uint16_t chan_prn_subevent_se(uint16_t chan_id,
uint16_t *prn_subevent_lu)
{
@ -268,27 +310,41 @@ static uint16_t chan_prn_subevent_se(uint16_t chan_id,
return prn_subevent_se;
}
/* Refer to Bluetooth Specification v5.2 Vol 6, Part B, Section 4.5.8.3
* Channel Selection algorithm #2, and Section 4.5.8.3.6 Subevent mapping to
* used channel index
*/
static uint8_t chan_d(uint8_t n)
{
uint8_t x, y;
/* Sub-expression to get natural number (N - 5) to be used in the
* calculation of d.
*/
if (n > 5) {
x = n - 5;
} else {
x = 0;
}
/* Sub-expression to get natural number ((N - 10) / 2) to be used in the
* calculation of d.
*/
if (n > 10) {
y = (n - 10) >> 1;
} else {
y = 0;
}
/* Calculate d using the above sub expressions */
return MAX(1, MAX(MIN(3, x), MIN(11, y)));
}
#endif /* CONFIG_BT_CTLR_ADV_ISO || CONFIG_BT_CTLR_SYNC_ISO */
#if defined(CONFIG_BT_CTLR_TEST)
/* Refer to Bluetooth Specification v5.2 Vol 6, Part C, Section 3 LE Channel
* Selection algorithm #2 sample data
*/
void lll_chan_sel_2_ut(void)
{
uint8_t chan_map_1[] = {0xFF, 0xFF, 0xFF, 0xFF, 0x1F};
@ -298,6 +354,8 @@ void lll_chan_sel_2_ut(void)
uint16_t const chan_id = 0x305F;
uint8_t m;
/* Tests when ISO not supported */
/* Section 3.1 Sample Data 1 (37 used channels) */
m = lll_chan_sel_2(0, chan_id, chan_map_1, chan_map_1_37_used);
LL_ASSERT(m == 25U);
@ -310,6 +368,7 @@ void lll_chan_sel_2_ut(void)
m = lll_chan_sel_2(3, chan_id, chan_map_1, chan_map_1_37_used);
LL_ASSERT(m == 21U);
/* Section 3.1 Sample Data 2 (9 used channels) */
m = lll_chan_sel_2(6, chan_id, chan_map_2, chan_map_2_9_used);
LL_ASSERT(m == 23U);
@ -340,6 +399,7 @@ void lll_chan_sel_2_ut(void)
prn_subevent_se = chan_prn_subevent_se(chan_id, &prn_subevent_lu);
LL_ASSERT(prn_subevent_se == 38198);
/* Section 3.1 Sample Data 1 (37 used channels) */
/* BIS subevent 1, event counter 0 */
m = lll_chan_iso_event(0, chan_id, chan_map_1, chan_map_1_37_used, &prn_s, &remap_idx);
LL_ASSERT((prn_s ^ chan_id) == 56857);
@ -424,6 +484,7 @@ void lll_chan_sel_2_ut(void)
LL_ASSERT(remap_idx == 8U);
LL_ASSERT(m == 8U);
/* Section 3.1 Sample Data 2 (9 used channels) */
/* BIS subevent 1, event counter 6 */
m = lll_chan_iso_event(6, chan_id, chan_map_2, chan_map_2_9_used, &prn_s, &remap_idx);
LL_ASSERT((prn_s ^ chan_id) == 10975);