/*
        Copyright (C) 2004 - 2009 Ivo van Doorn <IvDoorn@gmail.com>
        <http://rt2x00.serialmonkey.com>

        This program is free software; you can redistribute it and/or modify
        it under the terms of the GNU General Public License as published by
        the Free Software Foundation; either version 2 of the License, or
        (at your option) any later version.

        This program is distributed in the hope that it will be useful,
        but WITHOUT ANY WARRANTY; without even the implied warranty of
        MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
        GNU General Public License for more details.

        You should have received a copy of the GNU General Public License
        along with this program; if not, write to the
        Free Software Foundation, Inc.,
        59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

/*
        Module: rt2x00lib
        Abstract: rt2x00 generic link tuning routines.
 */

#include <linux/kernel.h>
#include <linux/module.h>

#include "rt2x00.h"
#include "rt2x00lib.h"

/*
 * When we lack RSSI information return something less then -80 to
 * tell the driver to tune the device to maximum sensitivity.
 */
#define DEFAULT_RSSI            -128

/*
 * Helper struct and macro to work with moving/walking averages.
 * When adding a value to the average value the following calculation
 * is needed:
 *
 *        avg_rssi = ((avg_rssi * 7) + rssi) / 8;
 *
 * The advantage of this approach is that we only need 1 variable
 * to store the average in (No need for a count and a total).
 * But more importantly, normal average values will over time
 * move less and less towards newly added values this results
 * that with link tuning, the device can have a very good RSSI
 * for a few minutes but when the device is moved away from the AP
 * the average will not decrease fast enough to compensate.
 * The walking average compensates this and will move towards
 * the new values correctly allowing a effective link tuning,
 * the speed of the average moving towards other values depends
 * on the value for the number of samples. The higher the number
 * of samples, the slower the average will move.
 * We use two variables to keep track of the average value to
 * compensate for the rounding errors. This can be a significant
 * error (>5dBm) if the factor is too low.
 */
#define AVG_SAMPLES     8
#define AVG_FACTOR      1000
#define MOVING_AVERAGE(__avg, __val) \
({ \
        struct avg_val __new; \
        __new.avg_weight = \
            (__avg).avg_weight  ? \
                ((((__avg).avg_weight * ((AVG_SAMPLES) - 1)) + \
                  ((__val) * (AVG_FACTOR))) / \
                 (AVG_SAMPLES)) : \
                ((__val) * (AVG_FACTOR)); \
        __new.avg = __new.avg_weight / (AVG_FACTOR); \
        __new; \
})

static int rt2x00link_antenna_get_link_rssi(struct rt2x00_dev *rt2x00dev)
{
        struct link_ant *ant = &rt2x00dev->link.ant;

        if (ant->rssi_ant.avg && rt2x00dev->link.qual.rx_success)
                return ant->rssi_ant.avg;
        return DEFAULT_RSSI;
}

static int rt2x00link_antenna_get_rssi_history(struct rt2x00_dev *rt2x00dev)
{
        struct link_ant *ant = &rt2x00dev->link.ant;

        if (ant->rssi_history)
                return ant->rssi_history;
        return DEFAULT_RSSI;
}

static void rt2x00link_antenna_update_rssi_history(struct rt2x00_dev *rt2x00dev,
                                                   int rssi)
{
        struct link_ant *ant = &rt2x00dev->link.ant;
        ant->rssi_history = rssi;
}

static void rt2x00link_antenna_reset(struct rt2x00_dev *rt2x00dev)
{
        rt2x00dev->link.ant.rssi_ant.avg = 0;
        rt2x00dev->link.ant.rssi_ant.avg_weight = 0;
}

static void rt2x00lib_antenna_diversity_sample(struct rt2x00_dev *rt2x00dev)
{
        struct link_ant *ant = &rt2x00dev->link.ant;
        struct antenna_setup new_ant;
        int other_antenna;

        int sample_current = rt2x00link_antenna_get_link_rssi(rt2x00dev);
        int sample_other = rt2x00link_antenna_get_rssi_history(rt2x00dev);

        memcpy(&new_ant, &ant->active, sizeof(new_ant));

        /*
         * We are done sampling. Now we should evaluate the results.
         */
        ant->flags &= ~ANTENNA_MODE_SAMPLE;

        /*
         * During the last period we have sampled the RSSI
         * from both antennas. It now is time to determine
         * which antenna demonstrated the best performance.
         * When we are already on the antenna with the best
         * performance, just create a good starting point
         * for the history and we are done.
         */
        if (sample_current >= sample_other) {
                rt2x00link_antenna_update_rssi_history(rt2x00dev,
                        sample_current);
                return;
        }

        other_antenna = (ant->active.rx == ANTENNA_A) ? ANTENNA_B : ANTENNA_A;

        if (ant->flags & ANTENNA_RX_DIVERSITY)
                new_ant.rx = other_antenna;

        if (ant->flags & ANTENNA_TX_DIVERSITY)
                new_ant.tx = other_antenna;

        rt2x00lib_config_antenna(rt2x00dev, new_ant);
}

static void rt2x00lib_antenna_diversity_eval(struct rt2x00_dev *rt2x00dev)
{
        struct link_ant *ant = &rt2x00dev->link.ant;
        struct antenna_setup new_ant;
        int rssi_curr;
        int rssi_old;

        memcpy(&new_ant, &ant->active, sizeof(new_ant));

        /*
         * Get current RSSI value along with the historical value,
         * after that update the history with the current value.
         */
        rssi_curr = rt2x00link_antenna_get_link_rssi(rt2x00dev);
        rssi_old = rt2x00link_antenna_get_rssi_history(rt2x00dev);
        rt2x00link_antenna_update_rssi_history(rt2x00dev, rssi_curr);

        /*
         * Legacy driver indicates that we should swap antenna's
         * when the difference in RSSI is greater that 5. This
         * also should be done when the RSSI was actually better
         * then the previous sample.
         * When the difference exceeds the threshold we should
         * sample the rssi from the other antenna to make a valid
         * comparison between the 2 antennas.
         */
        if (abs(rssi_curr - rssi_old) < 5)
                return;

        ant->flags |= ANTENNA_MODE_SAMPLE;

        if (ant->flags & ANTENNA_RX_DIVERSITY)
                new_ant.rx = (new_ant.rx == ANTENNA_A) ? ANTENNA_B : ANTENNA_A;

        if (ant->flags & ANTENNA_TX_DIVERSITY)
                new_ant.tx = (new_ant.tx == ANTENNA_A) ? ANTENNA_B : ANTENNA_A;

        rt2x00lib_config_antenna(rt2x00dev, new_ant);
}

static bool rt2x00lib_antenna_diversity(struct rt2x00_dev *rt2x00dev)
{
        struct link_ant *ant = &rt2x00dev->link.ant;

        /*
         * Determine if software diversity is enabled for
         * either the TX or RX antenna (or both).
         */
        if (!(ant->flags & ANTENNA_RX_DIVERSITY) &&
            !(ant->flags & ANTENNA_TX_DIVERSITY)) {
                ant->flags = 0;
                return true;
        }

        /*
         * If we have only sampled the data over the last period
         * we should now harvest the data. Otherwise just evaluate
         * the data. The latter should only be performed once
         * every 2 seconds.
         */
        if (ant->flags & ANTENNA_MODE_SAMPLE) {
                rt2x00lib_antenna_diversity_sample(rt2x00dev);
                return true;
        } else if (rt2x00dev->link.count & 1) {
                rt2x00lib_antenna_diversity_eval(rt2x00dev);
                return true;
        }

        return false;
}

void rt2x00link_update_stats(struct rt2x00_dev *rt2x00dev,
                             struct sk_buff *skb,
                             struct rxdone_entry_desc *rxdesc)
{
        struct link *link = &rt2x00dev->link;
        struct link_qual *qual = &rt2x00dev->link.qual;
        struct link_ant *ant = &rt2x00dev->link.ant;
        struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;

        /*
         * No need to update the stats for !=STA interfaces
         */
        if (!rt2x00dev->intf_sta_count)
                return;

        /*
         * Frame was received successfully since non-succesfull
         * frames would have been dropped by the hardware.
         */
        qual->rx_success++;

        /*
         * We are only interested in quality statistics from
         * beacons which came from the BSS which we are
         * associated with.
         */
        if (!ieee80211_is_beacon(hdr->frame_control) ||
            !(rxdesc->dev_flags & RXDONE_MY_BSS))
                return;

        /*
         * Update global RSSI
         */
        link->avg_rssi = MOVING_AVERAGE(link->avg_rssi, rxdesc->rssi);

        /*
         * Update antenna RSSI
         */
        ant->rssi_ant = MOVING_AVERAGE(ant->rssi_ant, rxdesc->rssi);
}

void rt2x00link_start_tuner(struct rt2x00_dev *rt2x00dev)
{
        struct link *link = &rt2x00dev->link;

        /*
         * Link tuning should only be performed when
         * an active sta interface exists. AP interfaces
         * don't need link tuning and monitor mode interfaces
         * should never have to work with link tuners.
         */
        if (!rt2x00dev->intf_sta_count)
                return;

        /**
         * While scanning, link tuning is disabled. By default
         * the most sensitive settings will be used to make sure
         * that all beacons and probe responses will be received
         * during the scan.
         */
        if (test_bit(DEVICE_STATE_SCANNING, &rt2x00dev->flags))
                return;

        rt2x00link_reset_tuner(rt2x00dev, false);

        if (test_bit(DEVICE_STATE_PRESENT, &rt2x00dev->flags))
                ieee80211_queue_delayed_work(rt2x00dev->hw,
                                             &link->work, LINK_TUNE_INTERVAL);
}

void rt2x00link_stop_tuner(struct rt2x00_dev *rt2x00dev)
{
        cancel_delayed_work_sync(&rt2x00dev->link.work);
}

void rt2x00link_reset_tuner(struct rt2x00_dev *rt2x00dev, bool antenna)
{
        struct link_qual *qual = &rt2x00dev->link.qual;
        u8 vgc_level = qual->vgc_level_reg;

        if (!test_bit(DEVICE_STATE_ENABLED_RADIO, &rt2x00dev->flags))
                return;

        /*
         * Reset link information.
         * Both the currently active vgc level as well as
         * the link tuner counter should be reset. Resetting
         * the counter is important for devices where the
         * device should only perform link tuning during the
         * first minute after being enabled.
         */
        rt2x00dev->link.count = 0;
        memset(qual, 0, sizeof(*qual));

        /*
         * Restore the VGC level as stored in the registers,
         * the driver can use this to determine if the register
         * must be updated during reset or not.
         */
        qual->vgc_level_reg = vgc_level;

        /*
         * Reset the link tuner.
         */
        rt2x00dev->ops->lib->reset_tuner(rt2x00dev, qual);

        if (antenna)
                rt2x00link_antenna_reset(rt2x00dev);
}

static void rt2x00link_reset_qual(struct rt2x00_dev *rt2x00dev)
{
        struct link_qual *qual = &rt2x00dev->link.qual;

        qual->rx_success = 0;
        qual->rx_failed = 0;
        qual->tx_success = 0;
        qual->tx_failed = 0;
}

static void rt2x00link_tuner(struct work_struct *work)
{
        struct rt2x00_dev *rt2x00dev =
            container_of(work, struct rt2x00_dev, link.work.work);
        struct link *link = &rt2x00dev->link;
        struct link_qual *qual = &rt2x00dev->link.qual;

        /*
         * When the radio is shutting down we should
         * immediately cease all link tuning.
         */
        if (!test_bit(DEVICE_STATE_ENABLED_RADIO, &rt2x00dev->flags) ||
            test_bit(DEVICE_STATE_SCANNING, &rt2x00dev->flags))
                return;

        /*
         * Update statistics.
         */
        rt2x00dev->ops->lib->link_stats(rt2x00dev, qual);
        rt2x00dev->low_level_stats.dot11FCSErrorCount += qual->rx_failed;

        /*
         * Update quality RSSI for link tuning,
         * when we have received some frames and we managed to
         * collect the RSSI data we could use this. Otherwise we
         * must fallback to the default RSSI value.
         */
        if (!link->avg_rssi.avg || !qual->rx_success)
                qual->rssi = DEFAULT_RSSI;
        else
                qual->rssi = link->avg_rssi.avg;

        /*
         * Check if link tuning is supported by the hardware, some hardware
         * do not support link tuning at all, while other devices can disable
         * the feature from the EEPROM.
         */
        if (test_bit(CAPABILITY_LINK_TUNING, &rt2x00dev->cap_flags))
                rt2x00dev->ops->lib->link_tuner(rt2x00dev, qual, link->count);

        /*
         * Send a signal to the led to update the led signal strength.
         */
        rt2x00leds_led_quality(rt2x00dev, qual->rssi);

        /*
         * Evaluate antenna setup, make this the last step when
         * rt2x00lib_antenna_diversity made changes the quality
         * statistics will be reset.
         */
        if (rt2x00lib_antenna_diversity(rt2x00dev))
                rt2x00link_reset_qual(rt2x00dev);

        /*
         * Increase tuner counter, and reschedule the next link tuner run.
         */
        link->count++;

        if (test_bit(DEVICE_STATE_PRESENT, &rt2x00dev->flags))
                ieee80211_queue_delayed_work(rt2x00dev->hw,
                                             &link->work, LINK_TUNE_INTERVAL);
}

void rt2x00link_start_watchdog(struct rt2x00_dev *rt2x00dev)
{
        struct link *link = &rt2x00dev->link;

        if (test_bit(DEVICE_STATE_PRESENT, &rt2x00dev->flags) &&
            rt2x00dev->ops->lib->watchdog)
                ieee80211_queue_delayed_work(rt2x00dev->hw,
                                             &link->watchdog_work,
                                             WATCHDOG_INTERVAL);
}

void rt2x00link_stop_watchdog(struct rt2x00_dev *rt2x00dev)
{
        cancel_delayed_work_sync(&rt2x00dev->link.watchdog_work);
}

static void rt2x00link_watchdog(struct work_struct *work)
{
        struct rt2x00_dev *rt2x00dev =
            container_of(work, struct rt2x00_dev, link.watchdog_work.work);
        struct link *link = &rt2x00dev->link;

        /*
         * When the radio is shutting down we should
         * immediately cease the watchdog monitoring.
         */
        if (!test_bit(DEVICE_STATE_ENABLED_RADIO, &rt2x00dev->flags))
                return;

        rt2x00dev->ops->lib->watchdog(rt2x00dev);

        if (test_bit(DEVICE_STATE_PRESENT, &rt2x00dev->flags))
                ieee80211_queue_delayed_work(rt2x00dev->hw,
                                             &link->watchdog_work,
                                             WATCHDOG_INTERVAL);
}

void rt2x00link_start_agc(struct rt2x00_dev *rt2x00dev)
{
        struct link *link = &rt2x00dev->link;

        if (test_bit(DEVICE_STATE_PRESENT, &rt2x00dev->flags) &&
            rt2x00dev->ops->lib->gain_calibration)
                ieee80211_queue_delayed_work(rt2x00dev->hw,
                                             &link->agc_work,
                                             AGC_INTERVAL);
}

void rt2x00link_start_vcocal(struct rt2x00_dev *rt2x00dev)
{
        struct link *link = &rt2x00dev->link;

        if (test_bit(DEVICE_STATE_PRESENT, &rt2x00dev->flags) &&
            rt2x00dev->ops->lib->vco_calibration)
                ieee80211_queue_delayed_work(rt2x00dev->hw,
                                             &link->vco_work,
                                             VCO_INTERVAL);
}

void rt2x00link_stop_agc(struct rt2x00_dev *rt2x00dev)
{
        cancel_delayed_work_sync(&rt2x00dev->link.agc_work);
}

void rt2x00link_stop_vcocal(struct rt2x00_dev *rt2x00dev)
{
        cancel_delayed_work_sync(&rt2x00dev->link.vco_work);
}

static void rt2x00link_agc(struct work_struct *work)
{
        struct rt2x00_dev *rt2x00dev =
            container_of(work, struct rt2x00_dev, link.agc_work.work);
        struct link *link = &rt2x00dev->link;

        /*
         * When the radio is shutting down we should
         * immediately cease the watchdog monitoring.
         */
        if (!test_bit(DEVICE_STATE_ENABLED_RADIO, &rt2x00dev->flags))
                return;

        rt2x00dev->ops->lib->gain_calibration(rt2x00dev);

        if (test_bit(DEVICE_STATE_PRESENT, &rt2x00dev->flags))
                ieee80211_queue_delayed_work(rt2x00dev->hw,
                                             &link->agc_work,
                                             AGC_INTERVAL);
}

static void rt2x00link_vcocal(struct work_struct *work)
{
        struct rt2x00_dev *rt2x00dev =
            container_of(work, struct rt2x00_dev, link.vco_work.work);
        struct link *link = &rt2x00dev->link;

        /*
         * When the radio is shutting down we should
         * immediately cease the VCO calibration.
         */
        if (!test_bit(DEVICE_STATE_ENABLED_RADIO, &rt2x00dev->flags))
                return;

        rt2x00dev->ops->lib->vco_calibration(rt2x00dev);

        if (test_bit(DEVICE_STATE_PRESENT, &rt2x00dev->flags))
                ieee80211_queue_delayed_work(rt2x00dev->hw,
                                             &link->vco_work,
                                             VCO_INTERVAL);
}

void rt2x00link_register(struct rt2x00_dev *rt2x00dev)
{
        INIT_DELAYED_WORK(&rt2x00dev->link.agc_work, rt2x00link_agc);
        if (test_bit(CAPABILITY_VCO_RECALIBRATION, &rt2x00dev->cap_flags))
                INIT_DELAYED_WORK(&rt2x00dev->link.vco_work, rt2x00link_vcocal);
        INIT_DELAYED_WORK(&rt2x00dev->link.watchdog_work, rt2x00link_watchdog);
        INIT_DELAYED_WORK(&rt2x00dev->link.work, rt2x00link_tuner);
}