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Bring in some 802.11n packet duration calculation functions from a mix of Sam/Rui and linux ath9k .

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This will eventually be used by rate control modules and by the TX
code for calculating packet duration when handling rts/cts protection.

Obtained from:	sam@, rpaulo@, linux ath9k
This commit is contained in:
Adrian Chadd 2011-01-28 08:35:55 +00:00
parent 0ddfc9486b
commit d054f3a866
2 changed files with 86 additions and 1 deletions
sys/dev/ath/ath_hal
ah.cah.h

72
sys/dev/ath/ath_hal/ah.c

@ -234,6 +234,78 @@ ath_hal_reverseBits(uint32_t val, uint32_t n)
return retval;
}
/* 802.11n related timing definitions */
#define OFDM_PLCP_BITS 22
#define HT_L_STF 8
#define HT_L_LTF 8
#define HT_L_SIG 4
#define HT_SIG 8
#define HT_STF 4
#define HT_LTF(n) ((n) * 4)
#define HT_RC_2_MCS(_rc) ((_rc) & 0xf)
#define HT_RC_2_STREAMS(_rc) ((((_rc) & 0x78) >> 3) + 1)
#define IS_HT_RATE(_rc) ( (_rc) & IEEE80211_RATE_MCS)
/*
* Calculate the duration of a packet whether it is 11n or legacy.
*/
uint32_t
ath_hal_pkt_txtime(struct ath_hal *ah, const HAL_RATE_TABLE *rates, uint32_t frameLen,
uint16_t rateix, HAL_BOOL isht40, HAL_BOOL shortPreamble)
{
uint8_t rc;
int numStreams;
rc = rates->info[rateix].rateCode;
/* Legacy rate? Return the old way */
if (! IS_HT_RATE(rc))
return ath_hal_computetxtime(ah, rates, frameLen, rateix, shortPreamble);
/* 11n frame - extract out the number of spatial streams */
numStreams = HT_RC_2_STREAMS(rc);
KASSERT(numStreams == 1 || numStreams == 2, ("number of spatial streams needs to be 1 or 2: MCS rate 0x%x!", rateix));
return ath_computedur_ht(frameLen, rc, numStreams, isht40, shortPreamble);
}
/*
* Calculate the transmit duration of an 11n frame.
* This only works for MCS0->MCS15.
*/
uint32_t
ath_computedur_ht(uint32_t frameLen, uint16_t rate, int streams, HAL_BOOL isht40,
HAL_BOOL isShortGI)
{
static const uint16_t ht20_bps[16] = {
26, 52, 78, 104, 156, 208, 234, 260,
52, 104, 156, 208, 312, 416, 468, 520
};
static const uint16_t ht40_bps[16] = {
54, 108, 162, 216, 324, 432, 486, 540,
108, 216, 324, 432, 648, 864, 972, 1080,
};
uint32_t bitsPerSymbol, numBits, numSymbols, txTime;
KASSERT(rate & IEEE80211_RATE_MCS, ("not mcs %d", rate));
KASSERT((rate &~ IEEE80211_RATE_MCS) < 16, ("bad mcs 0x%x", rate));
if (isht40)
bitsPerSymbol = ht40_bps[rate & 0xf];
else
bitsPerSymbol = ht20_bps[rate & 0xf];
numBits = OFDM_PLCP_BITS + (frameLen << 3);
numSymbols = howmany(numBits, bitsPerSymbol);
if (isShortGI)
txTime = ((numSymbols * 18) + 4) / 5; /* 3.6us */
else
txTime = numSymbols * 4; /* 4us */
return txTime + HT_L_STF + HT_L_LTF +
HT_L_SIG + HT_SIG + HT_STF + HT_LTF(streams);
}
/*
* Compute the time to transmit a frame of length frameLen bytes
* using the specified rate, phy, and short preamble setting.

15
sys/dev/ath/ath_hal/ah.h

@ -882,7 +882,20 @@ extern void __ahdecl ath_hal_process_noisefloor(struct ath_hal *ah);
extern u_int __ahdecl ath_hal_getwirelessmodes(struct ath_hal*);
/*
* Calculate the transmit duration of a frame.
* Calculate the packet TX time for a legacy or 11n frame
*/
extern uint32_t __ahdecl ath_hal_pkt_txtime(struct ath_hal *ah,
const HAL_RATE_TABLE *rates, uint32_t frameLen,
uint16_t rateix, HAL_BOOL isht40, HAL_BOOL shortPreamble);
/*
* Calculate the duration of an 11n frame.
*/
extern uint32_t __ahdecl ath_computedur_ht(uint32_t frameLen, uint16_t rate,
int streams, HAL_BOOL isht40, HAL_BOOL isShortGI);
/*
* Calculate the transmit duration of a legacy frame.
*/
extern uint16_t __ahdecl ath_hal_computetxtime(struct ath_hal *,
const HAL_RATE_TABLE *rates, uint32_t frameLen,