ath5k: Extend rate_duration

 * Extend ieee80211_generic_frame_duration to support the various
 bwmodes.

 * Better document what's going on with ack bitrates and update
 write_rate_duration to support the standard ack bitrates (when
 we don't set the high bit).

 * Get rid of set_ack_bitrate_high and introduce a flag on ath5k_hw
 for this (we only called the function on init anyway so there is no
 difference).

 Signed-off-by: Nick Kossifidis <mickflemm@gmail.com>

Signed-off-by: John W. Linville <linville@tuxdriver.com>

3 files changed, 129 insertions, 46 deletions

diff --git a/drivers/net/wireless/ath/ath5k/ath5k.h b/drivers/net/wireless/ath/ath5k/ath5k.h
index e11fc8f3919..7df5b46ab69 100644
--- a/drivers/net/wireless/ath/ath5k/ath5k.h
+++ b/drivers/net/wireless/ath/ath5k/ath5k.h
@@ -267,6 +267,15 @@
 #define AR5K_INIT_SIFS_HALF_RATE                32
 #define AR5K_INIT_SIFS_QUARTER_RATE             64
 
+/* Used to calculate tx time for non 5/10/40MHz
+ * operation */
+/* It's preamble time + signal time (16 + 4) */
+#define AR5K_INIT_OFDM_PREAMPLE_TIME            20
+/* Preamble time for 40MHz (turbo) operation (min ?) */
+#define AR5K_INIT_OFDM_PREAMBLE_TIME_MIN        14
+#define AR5K_INIT_OFDM_SYMBOL_TIME              4
+#define AR5K_INIT_OFDM_PLCP_BITS                22
+
 /* Rx latency for 5 and 10MHz operation (max ?) */
 #define AR5K_INIT_RX_LAT_MAX                    63
 /* Tx latencies from initvals (5212 only but no problem
@@ -1083,6 +1092,7 @@ struct ath5k_hw {
 
         u32                     ah_limit_tx_retries;
         u8                      ah_coverage_class;
+        bool                    ah_ack_bitrate_high;
         u8                      ah_bwmode;
 
         /* Antenna Control */
@@ -1248,8 +1258,6 @@ void ath5k_hw_set_tsf64(struct ath5k_hw *ah, u64 tsf64);
 void ath5k_hw_reset_tsf(struct ath5k_hw *ah);
 void ath5k_hw_init_beacon(struct ath5k_hw *ah, u32 next_beacon, u32 interval);
 bool ath5k_hw_check_beacon_timers(struct ath5k_hw *ah, int intval);
-/* ACK bit rate */
-void ath5k_hw_set_ack_bitrate_high(struct ath5k_hw *ah, bool high);
 /* Init function */
 void ath5k_hw_pcu_init(struct ath5k_hw *ah, enum nl80211_iftype op_mode,
                                                                 u8 mode);
diff --git a/drivers/net/wireless/ath/ath5k/base.c b/drivers/net/wireless/ath/ath5k/base.c
index 9af7e461a23..526d8bc412c 100644
--- a/drivers/net/wireless/ath/ath5k/base.c
+++ b/drivers/net/wireless/ath/ath5k/base.c
@@ -2420,7 +2420,9 @@ ath5k_init(struct ath5k_softc *sc)
         for (i = 0; i < common->keymax; i++)
                 ath_hw_keyreset(common, (u16) i);
 
-        ath5k_hw_set_ack_bitrate_high(ah, true);
+        /* Use higher rates for acks instead of base
+         * rate */
+        ah->ah_ack_bitrate_high = true;
 
         for (i = 0; i < ARRAY_SIZE(sc->bslot); i++)
                 sc->bslot[i] = NULL;
diff --git a/drivers/net/wireless/ath/ath5k/pcu.c b/drivers/net/wireless/ath/ath5k/pcu.c
index 2118f7048f3..e7f6be9cdf1 100644
--- a/drivers/net/wireless/ath/ath5k/pcu.c
+++ b/drivers/net/wireless/ath/ath5k/pcu.c
@@ -31,11 +31,100 @@
 #include "debug.h"
 #include "base.h"
 
+/*
+ * AR5212+ can use higher rates for ack transmition
+ * based on current tx rate instead of the base rate.
+ * It does this to better utilize channel usage.
+ * This is a mapping between G rates (that cover both
+ * CCK and OFDM) and ack rates that we use when setting
+ * rate -> duration table. This mapping is hw-based so
+ * don't change anything.
+ *
+ * To enable this functionality we must set
+ * ah->ah_ack_bitrate_high to true else base rate is
+ * used (1Mb for CCK, 6Mb for OFDM).
+ */
+static const unsigned int ack_rates_high[] =
+/* Tx   -> ACK  */
+/* 1Mb  -> 1Mb  */      { 0,
+/* 2MB  -> 2Mb  */      1,
+/* 5.5Mb -> 2Mb */      1,
+/* 11Mb -> 2Mb  */      1,
+/* 6Mb  -> 6Mb  */      4,
+/* 9Mb  -> 6Mb  */      4,
+/* 12Mb -> 12Mb */      6,
+/* 18Mb -> 12Mb */      6,
+/* 24Mb -> 24Mb */      8,
+/* 36Mb -> 24Mb */      8,
+/* 48Mb -> 24Mb */      8,
+/* 54Mb -> 24Mb */      8 };
+
 /*******************\
 * Helper functions *
 \*******************/
 
 /**
+ * ath5k_hw_get_frame_duration - Get tx time of a frame
+ *
+ * @ah: The &struct ath5k_hw
+ * @len: Frame's length in bytes
+ * @rate: The @struct ieee80211_rate
+ *
+ * Calculate tx duration of a frame given it's rate and length
+ * It extends ieee80211_generic_frame_duration for non standard
+ * bwmodes.
+ */
+int ath5k_hw_get_frame_duration(struct ath5k_hw *ah,
+                int len, struct ieee80211_rate *rate)
+{
+        struct ath5k_softc *sc = ah->ah_sc;
+        int sifs, preamble, plcp_bits, sym_time;
+        int bitrate, bits, symbols, symbol_bits;
+        int dur;
+
+        /* Fallback */
+        if (!ah->ah_bwmode) {
+                dur = ieee80211_generic_frame_duration(sc->hw,
+                                                NULL, len, rate);
+                return dur;
+        }
+
+        bitrate = rate->bitrate;
+        preamble = AR5K_INIT_OFDM_PREAMPLE_TIME;
+        plcp_bits = AR5K_INIT_OFDM_PLCP_BITS;
+        sym_time = AR5K_INIT_OFDM_SYMBOL_TIME;
+
+        switch (ah->ah_bwmode) {
+        case AR5K_BWMODE_40MHZ:
+                sifs = AR5K_INIT_SIFS_TURBO;
+                preamble = AR5K_INIT_OFDM_PREAMBLE_TIME_MIN;
+                break;
+        case AR5K_BWMODE_10MHZ:
+                sifs = AR5K_INIT_SIFS_HALF_RATE;
+                preamble *= 2;
+                sym_time *= 2;
+                break;
+        case AR5K_BWMODE_5MHZ:
+                sifs = AR5K_INIT_SIFS_QUARTER_RATE;
+                preamble *= 4;
+                sym_time *= 4;
+                break;
+        default:
+                sifs = AR5K_INIT_SIFS_DEFAULT_BG;
+                break;
+        }
+
+        bits = plcp_bits + (len << 3);
+        /* Bit rate is in 100Kbits */
+        symbol_bits = bitrate * sym_time;
+        symbols = DIV_ROUND_UP(bits * 10, symbol_bits);
+
+        dur = sifs + preamble + (sym_time * symbols);
+
+        return dur;
+}
+
+/**
  * ath5k_hw_get_default_slottime - Get the default slot time for current mode
  *
  * @ah: The &struct ath5k_hw
@@ -120,43 +209,11 @@ void ath5k_hw_update_mib_counters(struct ath5k_hw *ah)
         stats->beacons += ath5k_hw_reg_read(ah, AR5K_BEACON_CNT);
 }
 
-/**
- * ath5k_hw_set_ack_bitrate - set bitrate for ACKs
- *
- * @ah: The &struct ath5k_hw
- * @high: Flag to determine if we want to use high transmission rate
- * for ACKs or not
- *
- * If high flag is set, we tell hw to use a set of control rates based on
- * the current transmission rate (check out control_rates array inside reset.c).
- * If not hw just uses the lowest rate available for the current modulation
- * scheme being used (1Mbit for CCK and 6Mbits for OFDM).
- */
-void ath5k_hw_set_ack_bitrate_high(struct ath5k_hw *ah, bool high)
-{
-        if (ah->ah_version != AR5K_AR5212)
-                return;
-        else {
-                u32 val = AR5K_STA_ID1_BASE_RATE_11B | AR5K_STA_ID1_ACKCTS_6MB;
-                if (high)
-                        AR5K_REG_DISABLE_BITS(ah, AR5K_STA_ID1, val);
-                else
-                        AR5K_REG_ENABLE_BITS(ah, AR5K_STA_ID1, val);
-        }
-}
-
 
 /******************\
 * ACK/CTS Timeouts *
 \******************/
 
-/*
- * index into rates for control rates, we can set it up like this because
- * this is only used for AR5212 and we know it supports G mode
- */
-static const unsigned int control_rates[] =
-        { 0, 1, 1, 1, 4, 4, 6, 6, 8, 8, 8, 8 };
-
 /**
  * ath5k_hw_write_rate_duration - fill rate code to duration table
  *
@@ -164,7 +221,7 @@ static const unsigned int control_rates[] =
  * @mode: one of enum ath5k_driver_mode
  *
  * Write the rate code to duration table upon hw reset. This is a helper for
- * ath5k_hw_reset(). It seems all this is doing is setting an ACK timeout on
+ * ath5k_hw_pcu_init(). It seems all this is doing is setting an ACK timeout on
  * the hardware, based on current mode, for each rate. The rates which are
  * capable of short preamble (802.11b rates 2Mbps, 5.5Mbps, and 11Mbps) have
  * different rate code so we write their value twice (one for long preamble
@@ -172,23 +229,30 @@ static const unsigned int control_rates[] =
  *
  * Note: Band doesn't matter here, if we set the values for OFDM it works
  * on both a and g modes. So all we have to do is set values for all g rates
- * that include all OFDM and CCK rates. If we operate in turbo or xr/half/
- * quarter rate mode, we need to use another set of bitrates (that's why we
- * need the mode parameter) but we don't handle these proprietary modes yet.
+ * that include all OFDM and CCK rates.
+ *
  */
-static inline void ath5k_hw_write_rate_duration(struct ath5k_hw *ah,
-                                                unsigned int mode)
+static inline void ath5k_hw_write_rate_duration(struct ath5k_hw *ah)
 {
         struct ath5k_softc *sc = ah->ah_sc;
         struct ieee80211_rate *rate;
         unsigned int i;
+        /* 802.11g covers both OFDM and CCK */
+        u8 band = IEEE80211_BAND_2GHZ;
 
         /* Write rate duration table */
-        for (i = 0; i < sc->sbands[IEEE80211_BAND_2GHZ].n_bitrates; i++) {
+        for (i = 0; i < sc->sbands[band].n_bitrates; i++) {
                 u32 reg;
                 u16 tx_time;
 
-                rate = &sc->sbands[IEEE80211_BAND_2GHZ].bitrates[control_rates[i]];
+                if (ah->ah_ack_bitrate_high)
+                        rate = &sc->sbands[band].bitrates[ack_rates_high[i]];
+                /* CCK -> 1Mb */
+                else if (i < 4)
+                        rate = &sc->sbands[band].bitrates[0];
+                /* OFDM -> 6Mb */
+                else
+                        rate = &sc->sbands[band].bitrates[4];
 
                 /* Set ACK timeout */
                 reg = AR5K_RATE_DUR(rate->hw_value);
@@ -199,8 +263,9 @@ static inline void ath5k_hw_write_rate_duration(struct ath5k_hw *ah,
                  * actual rate for this rate. See mac80211 tx.c
                  * ieee80211_duration() for a brief description of
                  * what rate we should choose to TX ACKs. */
-                tx_time = le16_to_cpu(ieee80211_generic_frame_duration(sc->hw,
-                                                        NULL, 10, rate));
+                tx_time = ath5k_hw_get_frame_duration(ah, 10, rate);
+
+                tx_time = le16_to_cpu(tx_time);
 
                 ath5k_hw_reg_write(ah, tx_time, reg);
 
@@ -835,7 +900,7 @@ void ath5k_hw_pcu_init(struct ath5k_hw *ah, enum nl80211_iftype op_mode,
          * mac80211 are integrated */
         if (ah->ah_version == AR5K_AR5212 &&
                 ah->ah_sc->nvifs)
-                ath5k_hw_write_rate_duration(ah, mode);
+                ath5k_hw_write_rate_duration(ah);
 
         /* Set RSSI/BRSSI thresholds
          *
@@ -869,5 +934,13 @@ void ath5k_hw_pcu_init(struct ath5k_hw *ah, enum nl80211_iftype op_mode,
         if (ah->ah_coverage_class > 0)
                 ath5k_hw_set_coverage_class(ah, ah->ah_coverage_class);
 
+        /* Set ACK bitrate mode (see ack_rates_high) */
+        if (ah->ah_version == AR5K_AR5212) {
+                u32 val = AR5K_STA_ID1_BASE_RATE_11B | AR5K_STA_ID1_ACKCTS_6MB;
+                if (ah->ah_ack_bitrate_high)
+                        AR5K_REG_DISABLE_BITS(ah, AR5K_STA_ID1, val);
+                else
+                        AR5K_REG_ENABLE_BITS(ah, AR5K_STA_ID1, val);
+        }
         return;
 }