[ARM] pxa: Gumstix Verdex PCMCIA support

[linux-2.6/verdex.git] / drivers / net / wireless / iwlwifi / iwl-rx.c

/******************************************************************************
 *
 * Copyright(c) 2003 - 2009 Intel Corporation. All rights reserved.
 *
 * Portions of this file are derived from the ipw3945 project, as well
 * as portions of the ieee80211 subsystem header files.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of version 2 of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * 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.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110, USA
 *
 * The full GNU General Public License is included in this distribution in the
 * file called LICENSE.
 *
 * Contact Information:
 *  Intel Linux Wireless <ilw@linux.intel.com>
 * Intel Corporation, 5200 N.E. Elam Young Parkway, Hillsboro, OR 97124-6497
 *
 *****************************************************************************/

#include <linux/etherdevice.h>
#include <net/mac80211.h>
#include <asm/unaligned.h>
#include "iwl-eeprom.h"
#include "iwl-dev.h"
#include "iwl-core.h"
#include "iwl-sta.h"
#include "iwl-io.h"
#include "iwl-calib.h"
#include "iwl-helpers.h"
/************************** RX-FUNCTIONS ****************************/
/*
 * Rx theory of operation
 *
 * Driver allocates a circular buffer of Receive Buffer Descriptors (RBDs),
 * each of which point to Receive Buffers to be filled by the NIC.  These get
 * used not only for Rx frames, but for any command response or notification
 * from the NIC.  The driver and NIC manage the Rx buffers by means
 * of indexes into the circular buffer.
 *
 * Rx Queue Indexes
 * The host/firmware share two index registers for managing the Rx buffers.
 *
 * The READ index maps to the first position that the firmware may be writing
 * to -- the driver can read up to (but not including) this position and get
 * good data.
 * The READ index is managed by the firmware once the card is enabled.
 *
 * The WRITE index maps to the last position the driver has read from -- the
 * position preceding WRITE is the last slot the firmware can place a packet.
 *
 * The queue is empty (no good data) if WRITE = READ - 1, and is full if
 * WRITE = READ.
 *
 * During initialization, the host sets up the READ queue position to the first
 * INDEX position, and WRITE to the last (READ - 1 wrapped)
 *
 * When the firmware places a packet in a buffer, it will advance the READ index
 * and fire the RX interrupt.  The driver can then query the READ index and
 * process as many packets as possible, moving the WRITE index forward as it
 * resets the Rx queue buffers with new memory.
 *
 * The management in the driver is as follows:
 * + A list of pre-allocated SKBs is stored in iwl->rxq->rx_free.  When
 *   iwl->rxq->free_count drops to or below RX_LOW_WATERMARK, work is scheduled
 *   to replenish the iwl->rxq->rx_free.
 * + In iwl_rx_replenish (scheduled) if 'processed' != 'read' then the
 *   iwl->rxq is replenished and the READ INDEX is updated (updating the
 *   'processed' and 'read' driver indexes as well)
 * + A received packet is processed and handed to the kernel network stack,
 *   detached from the iwl->rxq.  The driver 'processed' index is updated.
 * + The Host/Firmware iwl->rxq is replenished at tasklet time from the rx_free
 *   list. If there are no allocated buffers in iwl->rxq->rx_free, the READ
 *   INDEX is not incremented and iwl->status(RX_STALLED) is set.  If there
 *   were enough free buffers and RX_STALLED is set it is cleared.
 *
 *
 * Driver sequence:
 *
 * iwl_rx_queue_alloc()   Allocates rx_free
 * iwl_rx_replenish()     Replenishes rx_free list from rx_used, and calls
 *                            iwl_rx_queue_restock
 * iwl_rx_queue_restock() Moves available buffers from rx_free into Rx
 *                            queue, updates firmware pointers, and updates
 *                            the WRITE index.  If insufficient rx_free buffers
 *                            are available, schedules iwl_rx_replenish
 *
 * -- enable interrupts --
 * ISR - iwl_rx()         Detach iwl_rx_mem_buffers from pool up to the
 *                            READ INDEX, detaching the SKB from the pool.
 *                            Moves the packet buffer from queue to rx_used.
 *                            Calls iwl_rx_queue_restock to refill any empty
 *                            slots.
 * ...
 *
 */

/**
 * iwl_rx_queue_space - Return number of free slots available in queue.
 */
int iwl_rx_queue_space(const struct iwl_rx_queue *q)
{
        int s = q->read - q->write;
        if (s <= 0)
                s += RX_QUEUE_SIZE;
        /* keep some buffer to not confuse full and empty queue */
        s -= 2;
        if (s < 0)
                s = 0;
        return s;
}
EXPORT_SYMBOL(iwl_rx_queue_space);

/**
 * iwl_rx_queue_update_write_ptr - Update the write pointer for the RX queue
 */
int iwl_rx_queue_update_write_ptr(struct iwl_priv *priv, struct iwl_rx_queue *q)
{
        unsigned long flags;
        u32 rx_wrt_ptr_reg = priv->hw_params.rx_wrt_ptr_reg;
        u32 reg;
        int ret = 0;

        spin_lock_irqsave(&q->lock, flags);

        if (q->need_update == 0)
                goto exit_unlock;

        /* If power-saving is in use, make sure device is awake */
        if (test_bit(STATUS_POWER_PMI, &priv->status)) {
                reg = iwl_read32(priv, CSR_UCODE_DRV_GP1);

                if (reg & CSR_UCODE_DRV_GP1_BIT_MAC_SLEEP) {
                        iwl_set_bit(priv, CSR_GP_CNTRL,
                                    CSR_GP_CNTRL_REG_FLAG_MAC_ACCESS_REQ);
                        goto exit_unlock;
                }

                q->write_actual = (q->write & ~0x7);
                iwl_write_direct32(priv, rx_wrt_ptr_reg, q->write_actual);

        /* Else device is assumed to be awake */
        } else {
                /* Device expects a multiple of 8 */
                q->write_actual = (q->write & ~0x7);
                iwl_write_direct32(priv, rx_wrt_ptr_reg, q->write_actual);
        }

        q->need_update = 0;

 exit_unlock:
        spin_unlock_irqrestore(&q->lock, flags);
        return ret;
}
EXPORT_SYMBOL(iwl_rx_queue_update_write_ptr);
/**
 * iwl_dma_addr2rbd_ptr - convert a DMA address to a uCode read buffer ptr
 */
static inline __le32 iwl_dma_addr2rbd_ptr(struct iwl_priv *priv,
                                          dma_addr_t dma_addr)
{
        return cpu_to_le32((u32)(dma_addr >> 8));
}

/**
 * iwl_rx_queue_restock - refill RX queue from pre-allocated pool
 *
 * If there are slots in the RX queue that need to be restocked,
 * and we have free pre-allocated buffers, fill the ranks as much
 * as we can, pulling from rx_free.
 *
 * This moves the 'write' index forward to catch up with 'processed', and
 * also updates the memory address in the firmware to reference the new
 * target buffer.
 */
int iwl_rx_queue_restock(struct iwl_priv *priv)
{
        struct iwl_rx_queue *rxq = &priv->rxq;
        struct list_head *element;
        struct iwl_rx_mem_buffer *rxb;
        unsigned long flags;
        int write;
        int ret = 0;

        spin_lock_irqsave(&rxq->lock, flags);
        write = rxq->write & ~0x7;
        while ((iwl_rx_queue_space(rxq) > 0) && (rxq->free_count)) {
                /* Get next free Rx buffer, remove from free list */
                element = rxq->rx_free.next;
                rxb = list_entry(element, struct iwl_rx_mem_buffer, list);
                list_del(element);

                /* Point to Rx buffer via next RBD in circular buffer */
                rxq->bd[rxq->write] = iwl_dma_addr2rbd_ptr(priv, rxb->aligned_dma_addr);
                rxq->queue[rxq->write] = rxb;
                rxq->write = (rxq->write + 1) & RX_QUEUE_MASK;
                rxq->free_count--;
        }
        spin_unlock_irqrestore(&rxq->lock, flags);
        /* If the pre-allocated buffer pool is dropping low, schedule to
         * refill it */
        if (rxq->free_count <= RX_LOW_WATERMARK)
                queue_work(priv->workqueue, &priv->rx_replenish);


        /* If we've added more space for the firmware to place data, tell it.
         * Increment device's write pointer in multiples of 8. */
        if (rxq->write_actual != (rxq->write & ~0x7)) {
                spin_lock_irqsave(&rxq->lock, flags);
                rxq->need_update = 1;
                spin_unlock_irqrestore(&rxq->lock, flags);
                ret = iwl_rx_queue_update_write_ptr(priv, rxq);
        }

        return ret;
}
EXPORT_SYMBOL(iwl_rx_queue_restock);


/**
 * iwl_rx_replenish - Move all used packet from rx_used to rx_free
 *
 * When moving to rx_free an SKB is allocated for the slot.
 *
 * Also restock the Rx queue via iwl_rx_queue_restock.
 * This is called as a scheduled work item (except for during initialization)
 */
void iwl_rx_allocate(struct iwl_priv *priv, gfp_t priority)
{
        struct iwl_rx_queue *rxq = &priv->rxq;
        struct list_head *element;
        struct iwl_rx_mem_buffer *rxb;
        struct sk_buff *skb;
        unsigned long flags;

        while (1) {
                spin_lock_irqsave(&rxq->lock, flags);
                if (list_empty(&rxq->rx_used)) {
                        spin_unlock_irqrestore(&rxq->lock, flags);
                        return;
                }
                spin_unlock_irqrestore(&rxq->lock, flags);

                if (rxq->free_count > RX_LOW_WATERMARK)
                        priority |= __GFP_NOWARN;
                /* Alloc a new receive buffer */
                skb = alloc_skb(priv->hw_params.rx_buf_size + 256,
                                                priority);

                if (!skb) {
                        if (net_ratelimit())
                                IWL_DEBUG_INFO(priv, "Failed to allocate SKB buffer.\n");
                        if ((rxq->free_count <= RX_LOW_WATERMARK) &&
                            net_ratelimit())
                                IWL_CRIT(priv, "Failed to allocate SKB buffer with %s. Only %u free buffers remaining.\n",
                                         priority == GFP_ATOMIC ?  "GFP_ATOMIC" : "GFP_KERNEL",
                                         rxq->free_count);
                        /* We don't reschedule replenish work here -- we will
                         * call the restock method and if it still needs
                         * more buffers it will schedule replenish */
                        break;
                }

                spin_lock_irqsave(&rxq->lock, flags);

                if (list_empty(&rxq->rx_used)) {
                        spin_unlock_irqrestore(&rxq->lock, flags);
                        dev_kfree_skb_any(skb);
                        return;
                }
                element = rxq->rx_used.next;
                rxb = list_entry(element, struct iwl_rx_mem_buffer, list);
                list_del(element);

                spin_unlock_irqrestore(&rxq->lock, flags);

                rxb->skb = skb;
                /* Get physical address of RB/SKB */
                rxb->real_dma_addr = pci_map_single(
                                        priv->pci_dev,
                                        rxb->skb->data,
                                        priv->hw_params.rx_buf_size + 256,
                                        PCI_DMA_FROMDEVICE);
                /* dma address must be no more than 36 bits */
                BUG_ON(rxb->real_dma_addr & ~DMA_BIT_MASK(36));
                /* and also 256 byte aligned! */
                rxb->aligned_dma_addr = ALIGN(rxb->real_dma_addr, 256);
                skb_reserve(rxb->skb, rxb->aligned_dma_addr - rxb->real_dma_addr);

                spin_lock_irqsave(&rxq->lock, flags);

                list_add_tail(&rxb->list, &rxq->rx_free);
                rxq->free_count++;
                priv->alloc_rxb_skb++;

                spin_unlock_irqrestore(&rxq->lock, flags);
        }
}

void iwl_rx_replenish(struct iwl_priv *priv)
{
        unsigned long flags;

        iwl_rx_allocate(priv, GFP_KERNEL);

        spin_lock_irqsave(&priv->lock, flags);
        iwl_rx_queue_restock(priv);
        spin_unlock_irqrestore(&priv->lock, flags);
}
EXPORT_SYMBOL(iwl_rx_replenish);

void iwl_rx_replenish_now(struct iwl_priv *priv)
{
        iwl_rx_allocate(priv, GFP_ATOMIC);

        iwl_rx_queue_restock(priv);
}
EXPORT_SYMBOL(iwl_rx_replenish_now);


/* Assumes that the skb field of the buffers in 'pool' is kept accurate.
 * If an SKB has been detached, the POOL needs to have its SKB set to NULL
 * This free routine walks the list of POOL entries and if SKB is set to
 * non NULL it is unmapped and freed
 */
void iwl_rx_queue_free(struct iwl_priv *priv, struct iwl_rx_queue *rxq)
{
        int i;
        for (i = 0; i < RX_QUEUE_SIZE + RX_FREE_BUFFERS; i++) {
                if (rxq->pool[i].skb != NULL) {
                        pci_unmap_single(priv->pci_dev,
                                         rxq->pool[i].real_dma_addr,
                                         priv->hw_params.rx_buf_size + 256,
                                         PCI_DMA_FROMDEVICE);
                        dev_kfree_skb(rxq->pool[i].skb);
                }
        }

        pci_free_consistent(priv->pci_dev, 4 * RX_QUEUE_SIZE, rxq->bd,
                            rxq->dma_addr);
        pci_free_consistent(priv->pci_dev, sizeof(struct iwl_rb_status),
                            rxq->rb_stts, rxq->rb_stts_dma);
        rxq->bd = NULL;
        rxq->rb_stts  = NULL;
}
EXPORT_SYMBOL(iwl_rx_queue_free);

int iwl_rx_queue_alloc(struct iwl_priv *priv)
{
        struct iwl_rx_queue *rxq = &priv->rxq;
        struct pci_dev *dev = priv->pci_dev;
        int i;

        spin_lock_init(&rxq->lock);
        INIT_LIST_HEAD(&rxq->rx_free);
        INIT_LIST_HEAD(&rxq->rx_used);

        /* Alloc the circular buffer of Read Buffer Descriptors (RBDs) */
        rxq->bd = pci_alloc_consistent(dev, 4 * RX_QUEUE_SIZE, &rxq->dma_addr);
        if (!rxq->bd)
                goto err_bd;

        rxq->rb_stts = pci_alloc_consistent(dev, sizeof(struct iwl_rb_status),
                                        &rxq->rb_stts_dma);
        if (!rxq->rb_stts)
                goto err_rb;

        /* Fill the rx_used queue with _all_ of the Rx buffers */
        for (i = 0; i < RX_FREE_BUFFERS + RX_QUEUE_SIZE; i++)
                list_add_tail(&rxq->pool[i].list, &rxq->rx_used);

        /* Set us so that we have processed and used all buffers, but have
         * not restocked the Rx queue with fresh buffers */
        rxq->read = rxq->write = 0;
        rxq->write_actual = 0;
        rxq->free_count = 0;
        rxq->need_update = 0;
        return 0;

err_rb:
        pci_free_consistent(priv->pci_dev, 4 * RX_QUEUE_SIZE, rxq->bd,
                            rxq->dma_addr);
err_bd:
        return -ENOMEM;
}
EXPORT_SYMBOL(iwl_rx_queue_alloc);

void iwl_rx_queue_reset(struct iwl_priv *priv, struct iwl_rx_queue *rxq)
{
        unsigned long flags;
        int i;
        spin_lock_irqsave(&rxq->lock, flags);
        INIT_LIST_HEAD(&rxq->rx_free);
        INIT_LIST_HEAD(&rxq->rx_used);
        /* Fill the rx_used queue with _all_ of the Rx buffers */
        for (i = 0; i < RX_FREE_BUFFERS + RX_QUEUE_SIZE; i++) {
                /* In the reset function, these buffers may have been allocated
                 * to an SKB, so we need to unmap and free potential storage */
                if (rxq->pool[i].skb != NULL) {
                        pci_unmap_single(priv->pci_dev,
                                         rxq->pool[i].real_dma_addr,
                                         priv->hw_params.rx_buf_size + 256,
                                         PCI_DMA_FROMDEVICE);
                        priv->alloc_rxb_skb--;
                        dev_kfree_skb(rxq->pool[i].skb);
                        rxq->pool[i].skb = NULL;
                }
                list_add_tail(&rxq->pool[i].list, &rxq->rx_used);
        }

        /* Set us so that we have processed and used all buffers, but have
         * not restocked the Rx queue with fresh buffers */
        rxq->read = rxq->write = 0;
        rxq->write_actual = 0;
        rxq->free_count = 0;
        spin_unlock_irqrestore(&rxq->lock, flags);
}

int iwl_rx_init(struct iwl_priv *priv, struct iwl_rx_queue *rxq)
{
        u32 rb_size;
        const u32 rfdnlog = RX_QUEUE_SIZE_LOG; /* 256 RBDs */
        u32 rb_timeout = 0; /* FIXME: RX_RB_TIMEOUT for all devices? */

        if (!priv->cfg->use_isr_legacy)
                rb_timeout = RX_RB_TIMEOUT;

        if (priv->cfg->mod_params->amsdu_size_8K)
                rb_size = FH_RCSR_RX_CONFIG_REG_VAL_RB_SIZE_8K;
        else
                rb_size = FH_RCSR_RX_CONFIG_REG_VAL_RB_SIZE_4K;

        /* Stop Rx DMA */
        iwl_write_direct32(priv, FH_MEM_RCSR_CHNL0_CONFIG_REG, 0);

        /* Reset driver's Rx queue write index */
        iwl_write_direct32(priv, FH_RSCSR_CHNL0_RBDCB_WPTR_REG, 0);

        /* Tell device where to find RBD circular buffer in DRAM */
        iwl_write_direct32(priv, FH_RSCSR_CHNL0_RBDCB_BASE_REG,
                           (u32)(rxq->dma_addr >> 8));

        /* Tell device where in DRAM to update its Rx status */
        iwl_write_direct32(priv, FH_RSCSR_CHNL0_STTS_WPTR_REG,
                           rxq->rb_stts_dma >> 4);

        /* Enable Rx DMA
         * FH_RCSR_CHNL0_RX_IGNORE_RXF_EMPTY is set because of HW bug in
         *      the credit mechanism in 5000 HW RX FIFO
         * Direct rx interrupts to hosts
         * Rx buffer size 4 or 8k
         * RB timeout 0x10
         * 256 RBDs
         */
        iwl_write_direct32(priv, FH_MEM_RCSR_CHNL0_CONFIG_REG,
                           FH_RCSR_RX_CONFIG_CHNL_EN_ENABLE_VAL |
                           FH_RCSR_CHNL0_RX_IGNORE_RXF_EMPTY |
                           FH_RCSR_CHNL0_RX_CONFIG_IRQ_DEST_INT_HOST_VAL |
                           FH_RCSR_CHNL0_RX_CONFIG_SINGLE_FRAME_MSK |
                           rb_size|
                           (rb_timeout << FH_RCSR_RX_CONFIG_REG_IRQ_RBTH_POS)|
                           (rfdnlog << FH_RCSR_RX_CONFIG_RBDCB_SIZE_POS));

        iwl_write32(priv, CSR_INT_COALESCING, 0x40);

        return 0;
}

int iwl_rxq_stop(struct iwl_priv *priv)
{

        /* stop Rx DMA */
        iwl_write_direct32(priv, FH_MEM_RCSR_CHNL0_CONFIG_REG, 0);
        iwl_poll_direct_bit(priv, FH_MEM_RSSR_RX_STATUS_REG,
                            FH_RSSR_CHNL0_RX_STATUS_CHNL_IDLE, 1000);

        return 0;
}
EXPORT_SYMBOL(iwl_rxq_stop);

void iwl_rx_missed_beacon_notif(struct iwl_priv *priv,
                                struct iwl_rx_mem_buffer *rxb)

{
        struct iwl_rx_packet *pkt = (struct iwl_rx_packet *)rxb->skb->data;
        struct iwl_missed_beacon_notif *missed_beacon;

        missed_beacon = &pkt->u.missed_beacon;
        if (le32_to_cpu(missed_beacon->consequtive_missed_beacons) > 5) {
                IWL_DEBUG_CALIB(priv, "missed bcn cnsq %d totl %d rcd %d expctd %d\n",
                    le32_to_cpu(missed_beacon->consequtive_missed_beacons),
                    le32_to_cpu(missed_beacon->total_missed_becons),
                    le32_to_cpu(missed_beacon->num_recvd_beacons),
                    le32_to_cpu(missed_beacon->num_expected_beacons));
                if (!test_bit(STATUS_SCANNING, &priv->status))
                        iwl_init_sensitivity(priv);
        }
}
EXPORT_SYMBOL(iwl_rx_missed_beacon_notif);


/* Calculate noise level, based on measurements during network silence just
 *   before arriving beacon.  This measurement can be done only if we know
 *   exactly when to expect beacons, therefore only when we're associated. */
static void iwl_rx_calc_noise(struct iwl_priv *priv)
{
        struct statistics_rx_non_phy *rx_info
                                = &(priv->statistics.rx.general);
        int num_active_rx = 0;
        int total_silence = 0;
        int bcn_silence_a =
                le32_to_cpu(rx_info->beacon_silence_rssi_a) & IN_BAND_FILTER;
        int bcn_silence_b =
                le32_to_cpu(rx_info->beacon_silence_rssi_b) & IN_BAND_FILTER;
        int bcn_silence_c =
                le32_to_cpu(rx_info->beacon_silence_rssi_c) & IN_BAND_FILTER;

        if (bcn_silence_a) {
                total_silence += bcn_silence_a;
                num_active_rx++;
        }
        if (bcn_silence_b) {
                total_silence += bcn_silence_b;
                num_active_rx++;
        }
        if (bcn_silence_c) {
                total_silence += bcn_silence_c;
                num_active_rx++;
        }

        /* Average among active antennas */
        if (num_active_rx)
                priv->last_rx_noise = (total_silence / num_active_rx) - 107;
        else
                priv->last_rx_noise = IWL_NOISE_MEAS_NOT_AVAILABLE;

        IWL_DEBUG_CALIB(priv, "inband silence a %u, b %u, c %u, dBm %d\n",
                        bcn_silence_a, bcn_silence_b, bcn_silence_c,
                        priv->last_rx_noise);
}

#define REG_RECALIB_PERIOD (60)

void iwl_rx_statistics(struct iwl_priv *priv,
                              struct iwl_rx_mem_buffer *rxb)
{
        int change;
        struct iwl_rx_packet *pkt = (struct iwl_rx_packet *)rxb->skb->data;

        IWL_DEBUG_RX(priv, "Statistics notification received (%d vs %d).\n",
                     (int)sizeof(priv->statistics),
                     le32_to_cpu(pkt->len_n_flags) & FH_RSCSR_FRAME_SIZE_MSK);

        change = ((priv->statistics.general.temperature !=
                   pkt->u.stats.general.temperature) ||
                  ((priv->statistics.flag &
                    STATISTICS_REPLY_FLG_HT40_MODE_MSK) !=
                   (pkt->u.stats.flag & STATISTICS_REPLY_FLG_HT40_MODE_MSK)));

        memcpy(&priv->statistics, &pkt->u.stats, sizeof(priv->statistics));

        set_bit(STATUS_STATISTICS, &priv->status);

        /* Reschedule the statistics timer to occur in
         * REG_RECALIB_PERIOD seconds to ensure we get a
         * thermal update even if the uCode doesn't give
         * us one */
        mod_timer(&priv->statistics_periodic, jiffies +
                  msecs_to_jiffies(REG_RECALIB_PERIOD * 1000));

        if (unlikely(!test_bit(STATUS_SCANNING, &priv->status)) &&
            (pkt->hdr.cmd == STATISTICS_NOTIFICATION)) {
                iwl_rx_calc_noise(priv);
                queue_work(priv->workqueue, &priv->run_time_calib_work);
        }

        iwl_leds_background(priv);

        if (priv->cfg->ops->lib->temp_ops.temperature && change)
                priv->cfg->ops->lib->temp_ops.temperature(priv);
}
EXPORT_SYMBOL(iwl_rx_statistics);

#define PERFECT_RSSI (-20) /* dBm */
#define WORST_RSSI (-95)   /* dBm */
#define RSSI_RANGE (PERFECT_RSSI - WORST_RSSI)

/* Calculate an indication of rx signal quality (a percentage, not dBm!).
 * See http://www.ces.clemson.edu/linux/signal_quality.shtml for info
 *   about formulas used below. */
static int iwl_calc_sig_qual(int rssi_dbm, int noise_dbm)
{
        int sig_qual;
        int degradation = PERFECT_RSSI - rssi_dbm;

        /* If we get a noise measurement, use signal-to-noise ratio (SNR)
         * as indicator; formula is (signal dbm - noise dbm).
         * SNR at or above 40 is a great signal (100%).
         * Below that, scale to fit SNR of 0 - 40 dB within 0 - 100% indicator.
         * Weakest usable signal is usually 10 - 15 dB SNR. */
        if (noise_dbm) {
                if (rssi_dbm - noise_dbm >= 40)
                        return 100;
                else if (rssi_dbm < noise_dbm)
                        return 0;
                sig_qual = ((rssi_dbm - noise_dbm) * 5) / 2;

        /* Else use just the signal level.
         * This formula is a least squares fit of data points collected and
         *   compared with a reference system that had a percentage (%) display
         *   for signal quality. */
        } else
                sig_qual = (100 * (RSSI_RANGE * RSSI_RANGE) - degradation *
                            (15 * RSSI_RANGE + 62 * degradation)) /
                           (RSSI_RANGE * RSSI_RANGE);

        if (sig_qual > 100)
                sig_qual = 100;
        else if (sig_qual < 1)
                sig_qual = 0;

        return sig_qual;
}

/* Calc max signal level (dBm) among 3 possible receivers */
static inline int iwl_calc_rssi(struct iwl_priv *priv,
                                struct iwl_rx_phy_res *rx_resp)
{
        return priv->cfg->ops->utils->calc_rssi(priv, rx_resp);
}

#ifdef CONFIG_IWLWIFI_DEBUG
/**
 * iwl_dbg_report_frame - dump frame to syslog during debug sessions
 *
 * You may hack this function to show different aspects of received frames,
 * including selective frame dumps.
 * group100 parameter selects whether to show 1 out of 100 good data frames.
 *    All beacon and probe response frames are printed.
 */
static void iwl_dbg_report_frame(struct iwl_priv *priv,
                      struct iwl_rx_phy_res *phy_res, u16 length,
                      struct ieee80211_hdr *header, int group100)
{
        u32 to_us;
        u32 print_summary = 0;
        u32 print_dump = 0;     /* set to 1 to dump all frames' contents */
        u32 hundred = 0;
        u32 dataframe = 0;
        __le16 fc;
        u16 seq_ctl;
        u16 channel;
        u16 phy_flags;
        u32 rate_n_flags;
        u32 tsf_low;
        int rssi;

        if (likely(!(iwl_get_debug_level(priv) & IWL_DL_RX)))
                return;

        /* MAC header */
        fc = header->frame_control;
        seq_ctl = le16_to_cpu(header->seq_ctrl);

        /* metadata */
        channel = le16_to_cpu(phy_res->channel);
        phy_flags = le16_to_cpu(phy_res->phy_flags);
        rate_n_flags = le32_to_cpu(phy_res->rate_n_flags);

        /* signal statistics */
        rssi = iwl_calc_rssi(priv, phy_res);
        tsf_low = le64_to_cpu(phy_res->timestamp) & 0x0ffffffff;

        to_us = !compare_ether_addr(header->addr1, priv->mac_addr);

        /* if data frame is to us and all is good,
         *   (optionally) print summary for only 1 out of every 100 */
        if (to_us && (fc & ~cpu_to_le16(IEEE80211_FCTL_PROTECTED)) ==
            cpu_to_le16(IEEE80211_FCTL_FROMDS | IEEE80211_FTYPE_DATA)) {
                dataframe = 1;
                if (!group100)
                        print_summary = 1;      /* print each frame */
                else if (priv->framecnt_to_us < 100) {
                        priv->framecnt_to_us++;
                        print_summary = 0;
                } else {
                        priv->framecnt_to_us = 0;
                        print_summary = 1;
                        hundred = 1;
                }
        } else {
                /* print summary for all other frames */
                print_summary = 1;
        }

        if (print_summary) {
                char *title;
                int rate_idx;
                u32 bitrate;

                if (hundred)
                        title = "100Frames";
                else if (ieee80211_has_retry(fc))
                        title = "Retry";
                else if (ieee80211_is_assoc_resp(fc))
                        title = "AscRsp";
                else if (ieee80211_is_reassoc_resp(fc))
                        title = "RasRsp";
                else if (ieee80211_is_probe_resp(fc)) {
                        title = "PrbRsp";
                        print_dump = 1; /* dump frame contents */
                } else if (ieee80211_is_beacon(fc)) {
                        title = "Beacon";
                        print_dump = 1; /* dump frame contents */
                } else if (ieee80211_is_atim(fc))
                        title = "ATIM";
                else if (ieee80211_is_auth(fc))
                        title = "Auth";
                else if (ieee80211_is_deauth(fc))
                        title = "DeAuth";
                else if (ieee80211_is_disassoc(fc))
                        title = "DisAssoc";
                else
                        title = "Frame";

                rate_idx = iwl_hwrate_to_plcp_idx(rate_n_flags);
                if (unlikely((rate_idx < 0) || (rate_idx >= IWL_RATE_COUNT))) {
                        bitrate = 0;
                        WARN_ON_ONCE(1);
                } else {
                        bitrate = iwl_rates[rate_idx].ieee / 2;
                }

                /* print frame summary.
                 * MAC addresses show just the last byte (for brevity),
                 *    but you can hack it to show more, if you'd like to. */
                if (dataframe)
                        IWL_DEBUG_RX(priv, "%s: mhd=0x%04x, dst=0x%02x, "
                                     "len=%u, rssi=%d, chnl=%d, rate=%u, \n",
                                     title, le16_to_cpu(fc), header->addr1[5],
                                     length, rssi, channel, bitrate);
                else {
                        /* src/dst addresses assume managed mode */
                        IWL_DEBUG_RX(priv, "%s: 0x%04x, dst=0x%02x, src=0x%02x, "
                                     "len=%u, rssi=%d, tim=%lu usec, "
                                     "phy=0x%02x, chnl=%d\n",
                                     title, le16_to_cpu(fc), header->addr1[5],
                                     header->addr3[5], length, rssi,
                                     tsf_low - priv->scan_start_tsf,
                                     phy_flags, channel);
                }
        }
        if (print_dump)
                iwl_print_hex_dump(priv, IWL_DL_RX, header, length);
}
#endif

/*
 * returns non-zero if packet should be dropped
 */
int iwl_set_decrypted_flag(struct iwl_priv *priv,
                           struct ieee80211_hdr *hdr,
                           u32 decrypt_res,
                           struct ieee80211_rx_status *stats)
{
        u16 fc = le16_to_cpu(hdr->frame_control);

        if (priv->active_rxon.filter_flags & RXON_FILTER_DIS_DECRYPT_MSK)
                return 0;

        if (!(fc & IEEE80211_FCTL_PROTECTED))
                return 0;

        IWL_DEBUG_RX(priv, "decrypt_res:0x%x\n", decrypt_res);
        switch (decrypt_res & RX_RES_STATUS_SEC_TYPE_MSK) {
        case RX_RES_STATUS_SEC_TYPE_TKIP:
                /* The uCode has got a bad phase 1 Key, pushes the packet.
                 * Decryption will be done in SW. */
                if ((decrypt_res & RX_RES_STATUS_DECRYPT_TYPE_MSK) ==
                    RX_RES_STATUS_BAD_KEY_TTAK)
                        break;

        case RX_RES_STATUS_SEC_TYPE_WEP:
                if ((decrypt_res & RX_RES_STATUS_DECRYPT_TYPE_MSK) ==
                    RX_RES_STATUS_BAD_ICV_MIC) {
                        /* bad ICV, the packet is destroyed since the
                         * decryption is inplace, drop it */
                        IWL_DEBUG_RX(priv, "Packet destroyed\n");
                        return -1;
                }
        case RX_RES_STATUS_SEC_TYPE_CCMP:
                if ((decrypt_res & RX_RES_STATUS_DECRYPT_TYPE_MSK) ==
                    RX_RES_STATUS_DECRYPT_OK) {
                        IWL_DEBUG_RX(priv, "hw decrypt successfully!!!\n");
                        stats->flag |= RX_FLAG_DECRYPTED;
                }
                break;

        default:
                break;
        }
        return 0;
}
EXPORT_SYMBOL(iwl_set_decrypted_flag);

static u32 iwl_translate_rx_status(struct iwl_priv *priv, u32 decrypt_in)
{
        u32 decrypt_out = 0;

        if ((decrypt_in & RX_RES_STATUS_STATION_FOUND) ==
                                        RX_RES_STATUS_STATION_FOUND)
                decrypt_out |= (RX_RES_STATUS_STATION_FOUND |
                                RX_RES_STATUS_NO_STATION_INFO_MISMATCH);

        decrypt_out |= (decrypt_in & RX_RES_STATUS_SEC_TYPE_MSK);

        /* packet was not encrypted */
        if ((decrypt_in & RX_RES_STATUS_SEC_TYPE_MSK) ==
                                        RX_RES_STATUS_SEC_TYPE_NONE)
                return decrypt_out;

        /* packet was encrypted with unknown alg */
        if ((decrypt_in & RX_RES_STATUS_SEC_TYPE_MSK) ==
                                        RX_RES_STATUS_SEC_TYPE_ERR)
                return decrypt_out;

        /* decryption was not done in HW */
        if ((decrypt_in & RX_MPDU_RES_STATUS_DEC_DONE_MSK) !=
                                        RX_MPDU_RES_STATUS_DEC_DONE_MSK)
                return decrypt_out;

        switch (decrypt_in & RX_RES_STATUS_SEC_TYPE_MSK) {

        case RX_RES_STATUS_SEC_TYPE_CCMP:
                /* alg is CCM: check MIC only */
                if (!(decrypt_in & RX_MPDU_RES_STATUS_MIC_OK))
                        /* Bad MIC */
                        decrypt_out |= RX_RES_STATUS_BAD_ICV_MIC;
                else
                        decrypt_out |= RX_RES_STATUS_DECRYPT_OK;

                break;

        case RX_RES_STATUS_SEC_TYPE_TKIP:
                if (!(decrypt_in & RX_MPDU_RES_STATUS_TTAK_OK)) {
                        /* Bad TTAK */
                        decrypt_out |= RX_RES_STATUS_BAD_KEY_TTAK;
                        break;
                }
                /* fall through if TTAK OK */
        default:
                if (!(decrypt_in & RX_MPDU_RES_STATUS_ICV_OK))
                        decrypt_out |= RX_RES_STATUS_BAD_ICV_MIC;
                else
                        decrypt_out |= RX_RES_STATUS_DECRYPT_OK;
                break;
        };

        IWL_DEBUG_RX(priv, "decrypt_in:0x%x  decrypt_out = 0x%x\n",
                                        decrypt_in, decrypt_out);

        return decrypt_out;
}

static void iwl_pass_packet_to_mac80211(struct iwl_priv *priv,
                                        struct ieee80211_hdr *hdr,
                                        u16 len,
                                        u32 ampdu_status,
                                        struct iwl_rx_mem_buffer *rxb,
                                        struct ieee80211_rx_status *stats)
{
        /* We only process data packets if the interface is open */
        if (unlikely(!priv->is_open)) {
                IWL_DEBUG_DROP_LIMIT(priv,
                    "Dropping packet while interface is not open.\n");
                return;
        }

        /* In case of HW accelerated crypto and bad decryption, drop */
        if (!priv->cfg->mod_params->sw_crypto &&
            iwl_set_decrypted_flag(priv, hdr, ampdu_status, stats))
                return;

        /* Resize SKB from mac header to end of packet */
        skb_reserve(rxb->skb, (void *)hdr - (void *)rxb->skb->data);
        skb_put(rxb->skb, len);

        iwl_update_stats(priv, false, hdr->frame_control, len);
        memcpy(IEEE80211_SKB_RXCB(rxb->skb), stats, sizeof(*stats));
        ieee80211_rx_irqsafe(priv->hw, rxb->skb);
        priv->alloc_rxb_skb--;
        rxb->skb = NULL;
}

/* This is necessary only for a number of statistics, see the caller. */
static int iwl_is_network_packet(struct iwl_priv *priv,
                struct ieee80211_hdr *header)
{
        /* Filter incoming packets to determine if they are targeted toward
         * this network, discarding packets coming from ourselves */
        switch (priv->iw_mode) {
        case NL80211_IFTYPE_ADHOC: /* Header: Dest. | Source    | BSSID */
                /* packets to our IBSS update information */
                return !compare_ether_addr(header->addr3, priv->bssid);
        case NL80211_IFTYPE_STATION: /* Header: Dest. | AP{BSSID} | Source */
                /* packets to our IBSS update information */
                return !compare_ether_addr(header->addr2, priv->bssid);
        default:
                return 1;
        }
}

/* Called for REPLY_RX (legacy ABG frames), or
 * REPLY_RX_MPDU_CMD (HT high-throughput N frames). */
void iwl_rx_reply_rx(struct iwl_priv *priv,
                                struct iwl_rx_mem_buffer *rxb)
{
        struct ieee80211_hdr *header;
        struct ieee80211_rx_status rx_status;
        struct iwl_rx_packet *pkt = (struct iwl_rx_packet *)rxb->skb->data;
        struct iwl_rx_phy_res *phy_res;
        __le32 rx_pkt_status;
        struct iwl4965_rx_mpdu_res_start *amsdu;
        u32 len;
        u32 ampdu_status;
        u16 fc;
        u32 rate_n_flags;

        /**
         * REPLY_RX and REPLY_RX_MPDU_CMD are handled differently.
         *      REPLY_RX: physical layer info is in this buffer
         *      REPLY_RX_MPDU_CMD: physical layer info was sent in separate
         *              command and cached in priv->last_phy_res
         *
         * Here we set up local variables depending on which command is
         * received.
         */
        if (pkt->hdr.cmd == REPLY_RX) {
                phy_res = (struct iwl_rx_phy_res *)pkt->u.raw;
                header = (struct ieee80211_hdr *)(pkt->u.raw + sizeof(*phy_res)
                                + phy_res->cfg_phy_cnt);

                len = le16_to_cpu(phy_res->byte_count);
                rx_pkt_status = *(__le32 *)(pkt->u.raw + sizeof(*phy_res) +
                                phy_res->cfg_phy_cnt + len);
                ampdu_status = le32_to_cpu(rx_pkt_status);
        } else {
                if (!priv->last_phy_res[0]) {
                        IWL_ERR(priv, "MPDU frame without cached PHY data\n");
                        return;
                }
                phy_res = (struct iwl_rx_phy_res *)&priv->last_phy_res[1];
                amsdu = (struct iwl4965_rx_mpdu_res_start *)pkt->u.raw;
                header = (struct ieee80211_hdr *)(pkt->u.raw + sizeof(*amsdu));
                len = le16_to_cpu(amsdu->byte_count);
                rx_pkt_status = *(__le32 *)(pkt->u.raw + sizeof(*amsdu) + len);
                ampdu_status = iwl_translate_rx_status(priv,
                                le32_to_cpu(rx_pkt_status));
        }

        if ((unlikely(phy_res->cfg_phy_cnt > 20))) {
                IWL_DEBUG_DROP(priv, "dsp size out of range [0,20]: %d/n",
                                phy_res->cfg_phy_cnt);
                return;
        }

        if (!(rx_pkt_status & RX_RES_STATUS_NO_CRC32_ERROR) ||
            !(rx_pkt_status & RX_RES_STATUS_NO_RXE_OVERFLOW)) {
                IWL_DEBUG_RX(priv, "Bad CRC or FIFO: 0x%08X.\n",
                                le32_to_cpu(rx_pkt_status));
                return;
        }

        /* This will be used in several places later */
        rate_n_flags = le32_to_cpu(phy_res->rate_n_flags);

        /* rx_status carries information about the packet to mac80211 */
        rx_status.mactime = le64_to_cpu(phy_res->timestamp);
        rx_status.freq =
                ieee80211_channel_to_frequency(le16_to_cpu(phy_res->channel));
        rx_status.band = (phy_res->phy_flags & RX_RES_PHY_FLAGS_BAND_24_MSK) ?
                                IEEE80211_BAND_2GHZ : IEEE80211_BAND_5GHZ;
        rx_status.rate_idx =
                iwl_hwrate_to_mac80211_idx(rate_n_flags, rx_status.band);
        rx_status.flag = 0;

        /* TSF isn't reliable. In order to allow smooth user experience,
         * this W/A doesn't propagate it to the mac80211 */
        /*rx_status.flag |= RX_FLAG_TSFT;*/

        priv->ucode_beacon_time = le32_to_cpu(phy_res->beacon_time_stamp);

        /* Find max signal strength (dBm) among 3 antenna/receiver chains */
        rx_status.signal = iwl_calc_rssi(priv, phy_res);

        /* Meaningful noise values are available only from beacon statistics,
         *   which are gathered only when associated, and indicate noise
         *   only for the associated network channel ...
         * Ignore these noise values while scanning (other channels) */
        if (iwl_is_associated(priv) &&
            !test_bit(STATUS_SCANNING, &priv->status)) {
                rx_status.noise = priv->last_rx_noise;
                rx_status.qual = iwl_calc_sig_qual(rx_status.signal,
                                                         rx_status.noise);
        } else {
                rx_status.noise = IWL_NOISE_MEAS_NOT_AVAILABLE;
                rx_status.qual = iwl_calc_sig_qual(rx_status.signal, 0);
        }

        /* Reset beacon noise level if not associated. */
        if (!iwl_is_associated(priv))
                priv->last_rx_noise = IWL_NOISE_MEAS_NOT_AVAILABLE;

#ifdef CONFIG_IWLWIFI_DEBUG
        /* Set "1" to report good data frames in groups of 100 */
        if (unlikely(iwl_get_debug_level(priv) & IWL_DL_RX))
                iwl_dbg_report_frame(priv, phy_res, len, header, 1);
#endif
        iwl_dbg_log_rx_data_frame(priv, len, header);
        IWL_DEBUG_STATS_LIMIT(priv, "Rssi %d, noise %d, qual %d, TSF %llu\n",
                rx_status.signal, rx_status.noise, rx_status.qual,
                (unsigned long long)rx_status.mactime);

        /*
         * "antenna number"
         *
         * It seems that the antenna field in the phy flags value
         * is actually a bit field. This is undefined by radiotap,
         * it wants an actual antenna number but I always get "7"
         * for most legacy frames I receive indicating that the
         * same frame was received on all three RX chains.
         *
         * I think this field should be removed in favor of a
         * new 802.11n radiotap field "RX chains" that is defined
         * as a bitmask.
         */
        rx_status.antenna =
                (le16_to_cpu(phy_res->phy_flags) & RX_RES_PHY_FLAGS_ANTENNA_MSK)
                >> RX_RES_PHY_FLAGS_ANTENNA_POS;

        /* set the preamble flag if appropriate */
        if (phy_res->phy_flags & RX_RES_PHY_FLAGS_SHORT_PREAMBLE_MSK)
                rx_status.flag |= RX_FLAG_SHORTPRE;

        /* Set up the HT phy flags */
        if (rate_n_flags & RATE_MCS_HT_MSK)
                rx_status.flag |= RX_FLAG_HT;
        if (rate_n_flags & RATE_MCS_HT40_MSK)
                rx_status.flag |= RX_FLAG_40MHZ;
        if (rate_n_flags & RATE_MCS_SGI_MSK)
                rx_status.flag |= RX_FLAG_SHORT_GI;

        if (iwl_is_network_packet(priv, header)) {
                priv->last_rx_rssi = rx_status.signal;
                priv->last_beacon_time =  priv->ucode_beacon_time;
                priv->last_tsf = le64_to_cpu(phy_res->timestamp);
        }

        fc = le16_to_cpu(header->frame_control);
        switch (fc & IEEE80211_FCTL_FTYPE) {
        case IEEE80211_FTYPE_MGMT:
        case IEEE80211_FTYPE_DATA:
                if (priv->iw_mode == NL80211_IFTYPE_AP)
                        iwl_update_ps_mode(priv, fc  & IEEE80211_FCTL_PM,
                                                header->addr2);
                /* fall through */
        default:
                iwl_pass_packet_to_mac80211(priv, header, len, ampdu_status,
                                rxb, &rx_status);
                break;

        }
}
EXPORT_SYMBOL(iwl_rx_reply_rx);

/* Cache phy data (Rx signal strength, etc) for HT frame (REPLY_RX_PHY_CMD).
 * This will be used later in iwl_rx_reply_rx() for REPLY_RX_MPDU_CMD. */
void iwl_rx_reply_rx_phy(struct iwl_priv *priv,
                                    struct iwl_rx_mem_buffer *rxb)
{
        struct iwl_rx_packet *pkt = (struct iwl_rx_packet *)rxb->skb->data;
        priv->last_phy_res[0] = 1;
        memcpy(&priv->last_phy_res[1], &(pkt->u.raw[0]),
               sizeof(struct iwl_rx_phy_res));
}
EXPORT_SYMBOL(iwl_rx_reply_rx_phy);