/*
 * Copyright (c) 2004-2008 Reyk Floeter <reyk@openbsd.org>
 * Copyright (c) 2006-2008 Nick Kossifidis <mickflemm@gmail.com>
 * Copyright (c) 2007-2008 Matthew W. S. Bell  <mentor@madwifi.org>
 * Copyright (c) 2007-2008 Luis Rodriguez <mcgrof@winlab.rutgers.edu>
 * Copyright (c) 2007-2008 Pavel Roskin <proski@gnu.org>
 * Copyright (c) 2007-2008 Jiri Slaby <jirislaby@gmail.com>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 *
 */

/*********************************\
* Protocol Control Unit Functions *
\*********************************/

#include <asm/unaligned.h>

#include "ath5k.h"
#include "reg.h"
#include "debug.h"

/**
 * DOC: Protocol Control Unit (PCU) functions
 *
 * Protocol control unit is responsible to maintain various protocol
 * properties before a frame is send and after a frame is received to/from
 * baseband. To be more specific, PCU handles:
 *
 * - Buffering of RX and TX frames (after QCU/DCUs)
 *
 * - Encrypting and decrypting (using the built-in engine)
 *
 * - Generating ACKs, RTS/CTS frames
 *
 * - Maintaining TSF
 *
 * - FCS
 *
 * - Updating beacon data (with TSF etc)
 *
 * - Generating virtual CCA
 *
 * - RX/Multicast filtering
 *
 * - BSSID filtering
 *
 * - Various statistics
 *
 * -Different operating modes: AP, STA, IBSS
 *
 * Note: Most of these functions can be tweaked/bypassed so you can do
 * them on sw above for debugging or research. For more infos check out PCU
 * registers on reg.h.
 */

/**
 * DOC: ACK rates
 *
 * AR5212+ can use higher rates for ack transmission
 * based on current tx rate instead of the base rate.
 * It does this to better utilize channel usage.
 * There 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
 * @shortpre: Indicate short preample
 *
 * 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, enum nl80211_band band,
                int len, struct ieee80211_rate *rate, bool shortpre)
{
        int sifs, preamble, plcp_bits, sym_time;
        int bitrate, bits, symbols, symbol_bits;
        int dur;

        /* Fallback */
        if (!ah->ah_bwmode) {
                __le16 raw_dur = ieee80211_generic_frame_duration(ah->hw,
                                        NULL, band, len, rate);

                /* subtract difference between long and short preamble */
                dur = le16_to_cpu(raw_dur);
                if (shortpre)
                        dur -= 96;

                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;
                bitrate = DIV_ROUND_UP(bitrate, 2);
                break;
        case AR5K_BWMODE_5MHZ:
                sifs = AR5K_INIT_SIFS_QUARTER_RATE;
                preamble *= 4;
                sym_time *= 4;
                bitrate = DIV_ROUND_UP(bitrate, 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
 */
unsigned int
ath5k_hw_get_default_slottime(struct ath5k_hw *ah)
{
        struct ieee80211_channel *channel = ah->ah_current_channel;
        unsigned int slot_time;

        switch (ah->ah_bwmode) {
        case AR5K_BWMODE_40MHZ:
                slot_time = AR5K_INIT_SLOT_TIME_TURBO;
                break;
        case AR5K_BWMODE_10MHZ:
                slot_time = AR5K_INIT_SLOT_TIME_HALF_RATE;
                break;
        case AR5K_BWMODE_5MHZ:
                slot_time = AR5K_INIT_SLOT_TIME_QUARTER_RATE;
                break;
        case AR5K_BWMODE_DEFAULT:
        default:
                slot_time = AR5K_INIT_SLOT_TIME_DEFAULT;
                if ((channel->hw_value == AR5K_MODE_11B) && !ah->ah_short_slot)
                        slot_time = AR5K_INIT_SLOT_TIME_B;
                break;
        }

        return slot_time;
}

/**
 * ath5k_hw_get_default_sifs() - Get the default SIFS for current mode
 * @ah: The &struct ath5k_hw
 */
unsigned int
ath5k_hw_get_default_sifs(struct ath5k_hw *ah)
{
        struct ieee80211_channel *channel = ah->ah_current_channel;
        unsigned int sifs;

        switch (ah->ah_bwmode) {
        case AR5K_BWMODE_40MHZ:
                sifs = AR5K_INIT_SIFS_TURBO;
                break;
        case AR5K_BWMODE_10MHZ:
                sifs = AR5K_INIT_SIFS_HALF_RATE;
                break;
        case AR5K_BWMODE_5MHZ:
                sifs = AR5K_INIT_SIFS_QUARTER_RATE;
                break;
        case AR5K_BWMODE_DEFAULT:
        default:
                sifs = AR5K_INIT_SIFS_DEFAULT_BG;
                if (channel->band == NL80211_BAND_5GHZ)
                        sifs = AR5K_INIT_SIFS_DEFAULT_A;
                break;
        }

        return sifs;
}

/**
 * ath5k_hw_update_mib_counters() - Update MIB counters (mac layer statistics)
 * @ah: The &struct ath5k_hw
 *
 * Reads MIB counters from PCU and updates sw statistics. Is called after a
 * MIB interrupt, because one of these counters might have reached their maximum
 * and triggered the MIB interrupt, to let us read and clear the counter.
 *
 * NOTE: Is called in interrupt context!
 */
void
ath5k_hw_update_mib_counters(struct ath5k_hw *ah)
{
        struct ath5k_statistics *stats = &ah->stats;

        /* Read-And-Clear */
        stats->ack_fail += ath5k_hw_reg_read(ah, AR5K_ACK_FAIL);
        stats->rts_fail += ath5k_hw_reg_read(ah, AR5K_RTS_FAIL);
        stats->rts_ok += ath5k_hw_reg_read(ah, AR5K_RTS_OK);
        stats->fcs_error += ath5k_hw_reg_read(ah, AR5K_FCS_FAIL);
        stats->beacons += ath5k_hw_reg_read(ah, AR5K_BEACON_CNT);
}


/******************\
* ACK/CTS Timeouts *
\******************/

/**
 * ath5k_hw_write_rate_duration() - Fill rate code to duration table
 * @ah: The &struct ath5k_hw
 *
 * Write the rate code to duration table upon hw reset. This is a helper for
 * 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
 * and one for short).
 *
 * 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.
 *
 */
static inline void
ath5k_hw_write_rate_duration(struct ath5k_hw *ah)
{
        struct ieee80211_rate *rate;
        unsigned int i;
        /* 802.11g covers both OFDM and CCK */
        u8 band = NL80211_BAND_2GHZ;

        /* Write rate duration table */
        for (i = 0; i < ah->sbands[band].n_bitrates; i++) {
                u32 reg;
                u16 tx_time;

                if (ah->ah_ack_bitrate_high)
                        rate = &ah->sbands[band].bitrates[ack_rates_high[i]];
                /* CCK -> 1Mb */
                else if (i < 4)
                        rate = &ah->sbands[band].bitrates[0];
                /* OFDM -> 6Mb */
                else
                        rate = &ah->sbands[band].bitrates[4];

                /* Set ACK timeout */
                reg = AR5K_RATE_DUR(rate->hw_value);

                /* An ACK frame consists of 10 bytes. If you add the FCS,
                 * which ieee80211_generic_frame_duration() adds,
                 * its 14 bytes. Note we use the control rate and not the
                 * 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 = ath5k_hw_get_frame_duration(ah, band, 10,
                                        rate, false);

                ath5k_hw_reg_write(ah, tx_time, reg);

                if (!(rate->flags & IEEE80211_RATE_SHORT_PREAMBLE))
                        continue;

                tx_time = ath5k_hw_get_frame_duration(ah, band, 10, rate, true);
                ath5k_hw_reg_write(ah, tx_time,
                        reg + (AR5K_SET_SHORT_PREAMBLE << 2));
        }
}

/**
 * ath5k_hw_set_ack_timeout() - Set ACK timeout on PCU
 * @ah: The &struct ath5k_hw
 * @timeout: Timeout in usec
 */
static int
ath5k_hw_set_ack_timeout(struct ath5k_hw *ah, unsigned int timeout)
{
        if (ath5k_hw_clocktoh(ah, AR5K_REG_MS(0xffffffff, AR5K_TIME_OUT_ACK))
                        <= timeout)
                return -EINVAL;

        AR5K_REG_WRITE_BITS(ah, AR5K_TIME_OUT, AR5K_TIME_OUT_ACK,
                ath5k_hw_htoclock(ah, timeout));

        return 0;
}

/**
 * ath5k_hw_set_cts_timeout() - Set CTS timeout on PCU
 * @ah: The &struct ath5k_hw
 * @timeout: Timeout in usec
 */
static int
ath5k_hw_set_cts_timeout(struct ath5k_hw *ah, unsigned int timeout)
{
        if (ath5k_hw_clocktoh(ah, AR5K_REG_MS(0xffffffff, AR5K_TIME_OUT_CTS))
                        <= timeout)
                return -EINVAL;

        AR5K_REG_WRITE_BITS(ah, AR5K_TIME_OUT, AR5K_TIME_OUT_CTS,
                        ath5k_hw_htoclock(ah, timeout));

        return 0;
}


/*******************\
* RX filter Control *
\*******************/

/**
 * ath5k_hw_set_lladdr() - Set station id
 * @ah: The &struct ath5k_hw
 * @mac: The card's mac address (array of octets)
 *
 * Set station id on hw using the provided mac address
 */
int
ath5k_hw_set_lladdr(struct ath5k_hw *ah, const u8 *mac)
{
        struct ath_common *common = ath5k_hw_common(ah);
        u32 low_id, high_id;
        u32 pcu_reg;

        /* Set new station ID */
        memcpy(common->macaddr, mac, ETH_ALEN);

        pcu_reg = ath5k_hw_reg_read(ah, AR5K_STA_ID1) & 0xffff0000;

        low_id = get_unaligned_le32(mac);
        high_id = get_unaligned_le16(mac + 4);

        ath5k_hw_reg_write(ah, low_id, AR5K_STA_ID0);
        ath5k_hw_reg_write(ah, pcu_reg | high_id, AR5K_STA_ID1);

        return 0;
}

/**
 * ath5k_hw_set_bssid() - Set current BSSID on hw
 * @ah: The &struct ath5k_hw
 *
 * Sets the current BSSID and BSSID mask we have from the
 * common struct into the hardware
 */
void
ath5k_hw_set_bssid(struct ath5k_hw *ah)
{
        struct ath_common *common = ath5k_hw_common(ah);
        u16 tim_offset = 0;

        /*
         * Set BSSID mask on 5212
         */
        if (ah->ah_version == AR5K_AR5212)
                ath_hw_setbssidmask(common);

        /*
         * Set BSSID
         */
        ath5k_hw_reg_write(ah,
                           get_unaligned_le32(common->curbssid),
                           AR5K_BSS_ID0);
        ath5k_hw_reg_write(ah,
                           get_unaligned_le16(common->curbssid + 4) |
                           ((common->curaid & 0x3fff) << AR5K_BSS_ID1_AID_S),
                           AR5K_BSS_ID1);

        if (common->curaid == 0) {
                ath5k_hw_disable_pspoll(ah);
                return;
        }

        AR5K_REG_WRITE_BITS(ah, AR5K_BEACON, AR5K_BEACON_TIM,
                            tim_offset ? tim_offset + 4 : 0);

        ath5k_hw_enable_pspoll(ah, NULL, 0);
}

/**
 * ath5k_hw_set_bssid_mask() - Filter out bssids we listen
 * @ah: The &struct ath5k_hw
 * @mask: The BSSID mask to set (array of octets)
 *
 * BSSID masking is a method used by AR5212 and newer hardware to inform PCU
 * which bits of the interface's MAC address should be looked at when trying
 * to decide which packets to ACK. In station mode and AP mode with a single
 * BSS every bit matters since we lock to only one BSS. In AP mode with
 * multiple BSSes (virtual interfaces) not every bit matters because hw must
 * accept frames for all BSSes and so we tweak some bits of our mac address
 * in order to have multiple BSSes.
 *
 * For more information check out ../hw.c of the common ath module.
 */
void
ath5k_hw_set_bssid_mask(struct ath5k_hw *ah, const u8 *mask)
{
        struct ath_common *common = ath5k_hw_common(ah);

        /* Cache bssid mask so that we can restore it
         * on reset */
        memcpy(common->bssidmask, mask, ETH_ALEN);
        if (ah->ah_version == AR5K_AR5212)
                ath_hw_setbssidmask(common);
}

/**
 * ath5k_hw_set_mcast_filter() - Set multicast filter
 * @ah: The &struct ath5k_hw
 * @filter0: Lower 32bits of muticast filter
 * @filter1: Higher 16bits of multicast filter
 */
void
ath5k_hw_set_mcast_filter(struct ath5k_hw *ah, u32 filter0, u32 filter1)
{
        ath5k_hw_reg_write(ah, filter0, AR5K_MCAST_FILTER0);
        ath5k_hw_reg_write(ah, filter1, AR5K_MCAST_FILTER1);
}

/**
 * ath5k_hw_get_rx_filter() - Get current rx filter
 * @ah: The &struct ath5k_hw
 *
 * Returns the RX filter by reading rx filter and
 * phy error filter registers. RX filter is used
 * to set the allowed frame types that PCU will accept
 * and pass to the driver. For a list of frame types
 * check out reg.h.
 */
u32
ath5k_hw_get_rx_filter(struct ath5k_hw *ah)
{
        u32 data, filter = 0;

        filter = ath5k_hw_reg_read(ah, AR5K_RX_FILTER);

        /*Radar detection for 5212*/
        if (ah->ah_version == AR5K_AR5212) {
                data = ath5k_hw_reg_read(ah, AR5K_PHY_ERR_FIL);

                if (data & AR5K_PHY_ERR_FIL_RADAR)
                        filter |= AR5K_RX_FILTER_RADARERR;
                if (data & (AR5K_PHY_ERR_FIL_OFDM | AR5K_PHY_ERR_FIL_CCK))
                        filter |= AR5K_RX_FILTER_PHYERR;
        }

        return filter;
}

/**
 * ath5k_hw_set_rx_filter() - Set rx filter
 * @ah: The &struct ath5k_hw
 * @filter: RX filter mask (see reg.h)
 *
 * Sets RX filter register and also handles PHY error filter
 * register on 5212 and newer chips so that we have proper PHY
 * error reporting.
 */
void
ath5k_hw_set_rx_filter(struct ath5k_hw *ah, u32 filter)
{
        u32 data = 0;

        /* Set PHY error filter register on 5212*/
        if (ah->ah_version == AR5K_AR5212) {
                if (filter & AR5K_RX_FILTER_RADARERR)
                        data |= AR5K_PHY_ERR_FIL_RADAR;
                if (filter & AR5K_RX_FILTER_PHYERR)
                        data |= AR5K_PHY_ERR_FIL_OFDM | AR5K_PHY_ERR_FIL_CCK;
        }

        /*
         * The AR5210 uses promiscuous mode to detect radar activity
         */
        if (ah->ah_version == AR5K_AR5210 &&
                        (filter & AR5K_RX_FILTER_RADARERR)) {
                filter &= ~AR5K_RX_FILTER_RADARERR;
                filter |= AR5K_RX_FILTER_PROM;
        }

        /*Zero length DMA (phy error reporting) */
        if (data)
                AR5K_REG_ENABLE_BITS(ah, AR5K_RXCFG, AR5K_RXCFG_ZLFDMA);
        else
                AR5K_REG_DISABLE_BITS(ah, AR5K_RXCFG, AR5K_RXCFG_ZLFDMA);

        /*Write RX Filter register*/
        ath5k_hw_reg_write(ah, filter & 0xff, AR5K_RX_FILTER);

        /*Write PHY error filter register on 5212*/
        if (ah->ah_version == AR5K_AR5212)
                ath5k_hw_reg_write(ah, data, AR5K_PHY_ERR_FIL);

}


/****************\
* Beacon control *
\****************/

#define ATH5K_MAX_TSF_READ 10

/**
 * ath5k_hw_get_tsf64() - Get the full 64bit TSF
 * @ah: The &struct ath5k_hw
 *
 * Returns the current TSF
 */
u64
ath5k_hw_get_tsf64(struct ath5k_hw *ah)
{
        u32 tsf_lower, tsf_upper1, tsf_upper2;
        int i;
        unsigned long flags;

        /* This code is time critical - we don't want to be interrupted here */
        local_irq_save(flags);

        /*
         * While reading TSF upper and then lower part, the clock is still
         * counting (or jumping in case of IBSS merge) so we might get
         * inconsistent values. To avoid this, we read the upper part again
         * and check it has not been changed. We make the hypothesis that a
         * maximum of 3 changes can happens in a row (we use 10 as a safe
         * value).
         *
         * Impact on performance is pretty small, since in most cases, only
         * 3 register reads are needed.
         */

        tsf_upper1 = ath5k_hw_reg_read(ah, AR5K_TSF_U32);
        for (i = 0; i < ATH5K_MAX_TSF_READ; i++) {
                tsf_lower = ath5k_hw_reg_read(ah, AR5K_TSF_L32);
                tsf_upper2 = ath5k_hw_reg_read(ah, AR5K_TSF_U32);
                if (tsf_upper2 == tsf_upper1)
                        break;
                tsf_upper1 = tsf_upper2;
        }

        local_irq_restore(flags);

        WARN_ON(i == ATH5K_MAX_TSF_READ);

        return ((u64)tsf_upper1 << 32) | tsf_lower;
}

#undef ATH5K_MAX_TSF_READ

/**
 * ath5k_hw_set_tsf64() - Set a new 64bit TSF
 * @ah: The &struct ath5k_hw
 * @tsf64: The new 64bit TSF
 *
 * Sets the new TSF
 */
void
ath5k_hw_set_tsf64(struct ath5k_hw *ah, u64 tsf64)
{
        ath5k_hw_reg_write(ah, tsf64 & 0xffffffff, AR5K_TSF_L32);
        ath5k_hw_reg_write(ah, (tsf64 >> 32) & 0xffffffff, AR5K_TSF_U32);
}

/**
 * ath5k_hw_reset_tsf() - Force a TSF reset
 * @ah: The &struct ath5k_hw
 *
 * Forces a TSF reset on PCU
 */
void
ath5k_hw_reset_tsf(struct ath5k_hw *ah)
{
        u32 val;

        val = ath5k_hw_reg_read(ah, AR5K_BEACON) | AR5K_BEACON_RESET_TSF;

        /*
         * Each write to the RESET_TSF bit toggles a hardware internal
         * signal to reset TSF, but if left high it will cause a TSF reset
         * on the next chip reset as well.  Thus we always write the value
         * twice to clear the signal.
         */
        ath5k_hw_reg_write(ah, val, AR5K_BEACON);
        ath5k_hw_reg_write(ah, val, AR5K_BEACON);
}

/**
 * ath5k_hw_init_beacon_timers() - Initialize beacon timers
 * @ah: The &struct ath5k_hw
 * @next_beacon: Next TBTT
 * @interval: Current beacon interval
 *
 * This function is used to initialize beacon timers based on current
 * operation mode and settings.
 */
void
ath5k_hw_init_beacon_timers(struct ath5k_hw *ah, u32 next_beacon, u32 interval)
{
        u32 timer1, timer2, timer3;

        /*
         * Set the additional timers by mode
         */
        switch (ah->opmode) {
        case NL80211_IFTYPE_MONITOR:
        case NL80211_IFTYPE_STATION:
                /* In STA mode timer1 is used as next wakeup
                 * timer and timer2 as next CFP duration start
                 * timer. Both in 1/8TUs. */
                /* TODO: PCF handling */
                if (ah->ah_version == AR5K_AR5210) {
                        timer1 = 0xffffffff;
                        timer2 = 0xffffffff;
                } else {
                        timer1 = 0x0000ffff;
                        timer2 = 0x0007ffff;
                }
                /* Mark associated AP as PCF incapable for now */
                AR5K_REG_DISABLE_BITS(ah, AR5K_STA_ID1, AR5K_STA_ID1_PCF);
                break;
        case NL80211_IFTYPE_ADHOC:
                AR5K_REG_ENABLE_BITS(ah, AR5K_TXCFG, AR5K_TXCFG_ADHOC_BCN_ATIM);
                /* fall through */
        default:
                /* On non-STA modes timer1 is used as next DMA
                 * beacon alert (DBA) timer and timer2 as next
                 * software beacon alert. Both in 1/8TUs. */
                timer1 = (next_beacon - AR5K_TUNE_DMA_BEACON_RESP) << 3;
                timer2 = (next_beacon - AR5K_TUNE_SW_BEACON_RESP) << 3;
                break;
        }

        /* Timer3 marks the end of our ATIM window
         * a zero length window is not allowed because
         * we 'll get no beacons */
        timer3 = next_beacon + 1;

        /*
         * Set the beacon register and enable all timers.
         */
        /* When in AP or Mesh Point mode zero timer0 to start TSF */
        if (ah->opmode == NL80211_IFTYPE_AP ||
            ah->opmode == NL80211_IFTYPE_MESH_POINT)
                ath5k_hw_reg_write(ah, 0, AR5K_TIMER0);

        ath5k_hw_reg_write(ah, next_beacon, AR5K_TIMER0);
        ath5k_hw_reg_write(ah, timer1, AR5K_TIMER1);
        ath5k_hw_reg_write(ah, timer2, AR5K_TIMER2);
        ath5k_hw_reg_write(ah, timer3, AR5K_TIMER3);

        /* Force a TSF reset if requested and enable beacons */
        if (interval & AR5K_BEACON_RESET_TSF)
                ath5k_hw_reset_tsf(ah);

        ath5k_hw_reg_write(ah, interval & (AR5K_BEACON_PERIOD |
                                        AR5K_BEACON_ENABLE),
                                                AR5K_BEACON);

        /* Flush any pending BMISS interrupts on ISR by
         * performing a clear-on-write operation on PISR
         * register for the BMISS bit (writing a bit on
         * ISR toggles a reset for that bit and leaves
         * the remaining bits intact) */
        if (ah->ah_version == AR5K_AR5210)
                ath5k_hw_reg_write(ah, AR5K_ISR_BMISS, AR5K_ISR);
        else
                ath5k_hw_reg_write(ah, AR5K_ISR_BMISS, AR5K_PISR);

        /* TODO: Set enhanced sleep registers on AR5212
         * based on vif->bss_conf params, until then
         * disable power save reporting.*/
        AR5K_REG_DISABLE_BITS(ah, AR5K_STA_ID1, AR5K_STA_ID1_PWR_SV);

}

/**
 * ath5k_check_timer_win() - Check if timer B is timer A + window
 * @a: timer a (before b)
 * @b: timer b (after a)
 * @window: difference between a and b
 * @intval: timers are increased by this interval
 *
 * This helper function checks if timer B is timer A + window and covers
 * cases where timer A or B might have already been updated or wrapped
 * around (Timers are 16 bit).
 *
 * Returns true if O.K.
 */
static inline bool
ath5k_check_timer_win(int a, int b, int window, int intval)
{
        /*
         * 1.) usually B should be A + window
         * 2.) A already updated, B not updated yet
         * 3.) A already updated and has wrapped around
         * 4.) B has wrapped around
         */
        if ((b - a == window) ||                                /* 1.) */
            (a - b == intval - window) ||                       /* 2.) */
            ((a | 0x10000) - b == intval - window) ||           /* 3.) */
            ((b | 0x10000) - a == window))                      /* 4.) */
                return true; /* O.K. */
        return false;
}

/**
 * ath5k_hw_check_beacon_timers() - Check if the beacon timers are correct
 * @ah: The &struct ath5k_hw
 * @intval: beacon interval
 *
 * This is a workaround for IBSS mode
 *
 * The need for this function arises from the fact that we have 4 separate
 * HW timer registers (TIMER0 - TIMER3), which are closely related to the
 * next beacon target time (NBTT), and that the HW updates these timers
 * separately based on the current TSF value. The hardware increments each
 * timer by the beacon interval, when the local TSF converted to TU is equal
 * to the value stored in the timer.
 *
 * The reception of a beacon with the same BSSID can update the local HW TSF
 * at any time - this is something we can't avoid. If the TSF jumps to a
 * time which is later than the time stored in a timer, this timer will not
 * be updated until the TSF in TU wraps around at 16 bit (the size of the
 * timers) and reaches the time which is stored in the timer.
 *
 * The problem is that these timers are closely related to TIMER0 (NBTT) and
 * that they define a time "window". When the TSF jumps between two timers
 * (e.g. ATIM and NBTT), the one in the past will be left behind (not
 * updated), while the one in the future will be updated every beacon
 * interval. This causes the window to get larger, until the TSF wraps
 * around as described above and the timer which was left behind gets
 * updated again. But - because the beacon interval is usually not an exact
 * divisor of the size of the timers (16 bit), an unwanted "window" between
 * these timers has developed!
 *
 * This is especially important with the ATIM window, because during
 * the ATIM window only ATIM frames and no data frames are allowed to be
 * sent, which creates transmission pauses after each beacon. This symptom
 * has been described as "ramping ping" because ping times increase linearly
 * for some time and then drop down again. A wrong window on the DMA beacon
 * timer has the same effect, so we check for these two conditions.
 *
 * Returns true if O.K.
 */
bool
ath5k_hw_check_beacon_timers(struct ath5k_hw *ah, int intval)
{
        unsigned int nbtt, atim, dma;

        nbtt = ath5k_hw_reg_read(ah, AR5K_TIMER0);
        atim = ath5k_hw_reg_read(ah, AR5K_TIMER3);
        dma = ath5k_hw_reg_read(ah, AR5K_TIMER1) >> 3;

        /* NOTE: SWBA is different. Having a wrong window there does not
         * stop us from sending data and this condition is caught by
         * other means (SWBA interrupt) */

        if (ath5k_check_timer_win(nbtt, atim, 1, intval) &&
            ath5k_check_timer_win(dma, nbtt, AR5K_TUNE_DMA_BEACON_RESP,
                                  intval))
                return true; /* O.K. */
        return false;
}

/**
 * ath5k_hw_set_coverage_class() - Set IEEE 802.11 coverage class
 * @ah: The &struct ath5k_hw
 * @coverage_class: IEEE 802.11 coverage class number
 *
 * Sets IFS intervals and ACK/CTS timeouts for given coverage class.
 */
void
ath5k_hw_set_coverage_class(struct ath5k_hw *ah, u8 coverage_class)
{
        /* As defined by IEEE 802.11-2007 17.3.8.6 */
        int slot_time = ath5k_hw_get_default_slottime(ah) + 3 * coverage_class;
        int ack_timeout = ath5k_hw_get_default_sifs(ah) + slot_time;
        int cts_timeout = ack_timeout;

        ath5k_hw_set_ifs_intervals(ah, slot_time);
        ath5k_hw_set_ack_timeout(ah, ack_timeout);
        ath5k_hw_set_cts_timeout(ah, cts_timeout);

        ah->ah_coverage_class = coverage_class;
}

/***************************\
* Init/Start/Stop functions *
\***************************/

/**
 * ath5k_hw_start_rx_pcu() - Start RX engine
 * @ah: The &struct ath5k_hw
 *
 * Starts RX engine on PCU so that hw can process RXed frames
 * (ACK etc).
 *
 * NOTE: RX DMA should be already enabled using ath5k_hw_start_rx_dma
 */
void
ath5k_hw_start_rx_pcu(struct ath5k_hw *ah)
{
        AR5K_REG_DISABLE_BITS(ah, AR5K_DIAG_SW, AR5K_DIAG_SW_DIS_RX);
}

/**
 * at5k_hw_stop_rx_pcu() - Stop RX engine
 * @ah: The &struct ath5k_hw
 *
 * Stops RX engine on PCU
 */
void
ath5k_hw_stop_rx_pcu(struct ath5k_hw *ah)
{
        AR5K_REG_ENABLE_BITS(ah, AR5K_DIAG_SW, AR5K_DIAG_SW_DIS_RX);
}

/**
 * ath5k_hw_set_opmode() - Set PCU operating mode
 * @ah: The &struct ath5k_hw
 * @op_mode: One of enum nl80211_iftype
 *
 * Configure PCU for the various operating modes (AP/STA etc)
 */
int
ath5k_hw_set_opmode(struct ath5k_hw *ah, enum nl80211_iftype op_mode)
{
        struct ath_common *common = ath5k_hw_common(ah);
        u32 pcu_reg, beacon_reg, low_id, high_id;

        ATH5K_DBG(ah, ATH5K_DEBUG_MODE, "mode %d\n", op_mode);

        /* Preserve rest settings */
        pcu_reg = ath5k_hw_reg_read(ah, AR5K_STA_ID1) & 0xffff0000;
        pcu_reg &= ~(AR5K_STA_ID1_ADHOC | AR5K_STA_ID1_AP
                        | AR5K_STA_ID1_KEYSRCH_MODE
                        | (ah->ah_version == AR5K_AR5210 ?
                        (AR5K_STA_ID1_PWR_SV | AR5K_STA_ID1_NO_PSPOLL) : 0));

        beacon_reg = 0;

        switch (op_mode) {
        case NL80211_IFTYPE_ADHOC:
                pcu_reg |= AR5K_STA_ID1_ADHOC | AR5K_STA_ID1_KEYSRCH_MODE;
                beacon_reg |= AR5K_BCR_ADHOC;
                if (ah->ah_version == AR5K_AR5210)
                        pcu_reg |= AR5K_STA_ID1_NO_PSPOLL;
                else
                        AR5K_REG_ENABLE_BITS(ah, AR5K_CFG, AR5K_CFG_IBSS);
                break;

        case NL80211_IFTYPE_AP:
        case NL80211_IFTYPE_MESH_POINT:
                pcu_reg |= AR5K_STA_ID1_AP | AR5K_STA_ID1_KEYSRCH_MODE;
                beacon_reg |= AR5K_BCR_AP;
                if (ah->ah_version == AR5K_AR5210)
                        pcu_reg |= AR5K_STA_ID1_NO_PSPOLL;
                else
                        AR5K_REG_DISABLE_BITS(ah, AR5K_CFG, AR5K_CFG_IBSS);
                break;

        case NL80211_IFTYPE_STATION:
                pcu_reg |= AR5K_STA_ID1_KEYSRCH_MODE
                        | (ah->ah_version == AR5K_AR5210 ?
                                AR5K_STA_ID1_PWR_SV : 0);
                /* fall through */
        case NL80211_IFTYPE_MONITOR:
                pcu_reg |= AR5K_STA_ID1_KEYSRCH_MODE
                        | (ah->ah_version == AR5K_AR5210 ?
                                AR5K_STA_ID1_NO_PSPOLL : 0);
                break;

        default:
                return -EINVAL;
        }

        /*
         * Set PCU registers
         */
        low_id = get_unaligned_le32(common->macaddr);
        high_id = get_unaligned_le16(common->macaddr + 4);
        ath5k_hw_reg_write(ah, low_id, AR5K_STA_ID0);
        ath5k_hw_reg_write(ah, pcu_reg | high_id, AR5K_STA_ID1);

        /*
         * Set Beacon Control Register on 5210
         */
        if (ah->ah_version == AR5K_AR5210)
                ath5k_hw_reg_write(ah, beacon_reg, AR5K_BCR);

        return 0;
}

/**
 * ath5k_hw_pcu_init() - Initialize PCU
 * @ah: The &struct ath5k_hw
 * @op_mode: One of enum nl80211_iftype
 * @mode: One of enum ath5k_driver_mode
 *
 * This function is used to initialize PCU by setting current
 * operation mode and various other settings.
 */
void
ath5k_hw_pcu_init(struct ath5k_hw *ah, enum nl80211_iftype op_mode)
{
        /* Set bssid and bssid mask */
        ath5k_hw_set_bssid(ah);

        /* Set PCU config */
        ath5k_hw_set_opmode(ah, op_mode);

        /* Write rate duration table only on AR5212 and if
         * virtual interface has already been brought up
         * XXX: rethink this after new mode changes to
         * mac80211 are integrated */
        if (ah->ah_version == AR5K_AR5212 &&
                ah->nvifs)
                ath5k_hw_write_rate_duration(ah);

        /* Set RSSI/BRSSI thresholds
         *
         * Note: If we decide to set this value
         * dynamically, have in mind that when AR5K_RSSI_THR
         * register is read it might return 0x40 if we haven't
         * wrote anything to it plus BMISS RSSI threshold is zeroed.
         * So doing a save/restore procedure here isn't the right
         * choice. Instead store it on ath5k_hw */
        ath5k_hw_reg_write(ah, (AR5K_TUNE_RSSI_THRES |
                                AR5K_TUNE_BMISS_THRES <<
                                AR5K_RSSI_THR_BMISS_S),
                                AR5K_RSSI_THR);

        /* MIC QoS support */
        if (ah->ah_mac_srev >= AR5K_SREV_AR2413) {
                ath5k_hw_reg_write(ah, 0x000100aa, AR5K_MIC_QOS_CTL);
                ath5k_hw_reg_write(ah, 0x00003210, AR5K_MIC_QOS_SEL);
        }

        /* QoS NOACK Policy */
        if (ah->ah_version == AR5K_AR5212) {
                ath5k_hw_reg_write(ah,
                        AR5K_REG_SM(2, AR5K_QOS_NOACK_2BIT_VALUES) |
                        AR5K_REG_SM(5, AR5K_QOS_NOACK_BIT_OFFSET)  |
                        AR5K_REG_SM(0, AR5K_QOS_NOACK_BYTE_OFFSET),
                        AR5K_QOS_NOACK);
        }

        /* Restore slot time and ACK timeouts */
        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;
}