linux/drivers/net/wireless/ath/hw.c
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   1/*
   2 * Copyright (c) 2009 Atheros Communications Inc.
   3 *
   4 * Permission to use, copy, modify, and/or distribute this software for any
   5 * purpose with or without fee is hereby granted, provided that the above
   6 * copyright notice and this permission notice appear in all copies.
   7 *
   8 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
   9 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  10 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  11 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  12 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  13 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  14 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  15 */
  16
  17#include <linux/export.h>
  18#include <asm/unaligned.h>
  19
  20#include "ath.h"
  21#include "reg.h"
  22
  23#define REG_READ                        (common->ops->read)
  24#define REG_WRITE(_ah, _reg, _val)      (common->ops->write)(_ah, _val, _reg)
  25
  26/**
  27 * ath_hw_set_bssid_mask - filter out bssids we listen
  28 *
  29 * @common: the ath_common struct for the device.
  30 *
  31 * BSSID masking is a method used by AR5212 and newer hardware to inform PCU
  32 * which bits of the interface's MAC address should be looked at when trying
  33 * to decide which packets to ACK. In station mode and AP mode with a single
  34 * BSS every bit matters since we lock to only one BSS. In AP mode with
  35 * multiple BSSes (virtual interfaces) not every bit matters because hw must
  36 * accept frames for all BSSes and so we tweak some bits of our mac address
  37 * in order to have multiple BSSes.
  38 *
  39 * NOTE: This is a simple filter and does *not* filter out all
  40 * relevant frames. Some frames that are not for us might get ACKed from us
  41 * by PCU because they just match the mask.
  42 *
  43 * When handling multiple BSSes you can get the BSSID mask by computing the
  44 * set of  ~ ( MAC XOR BSSID ) for all bssids we handle.
  45 *
  46 * When you do this you are essentially computing the common bits of all your
  47 * BSSes. Later it is assumed the hardware will "and" (&) the BSSID mask with
  48 * the MAC address to obtain the relevant bits and compare the result with
  49 * (frame's BSSID & mask) to see if they match.
  50 *
  51 * Simple example: on your card you have have two BSSes you have created with
  52 * BSSID-01 and BSSID-02. Lets assume BSSID-01 will not use the MAC address.
  53 * There is another BSSID-03 but you are not part of it. For simplicity's sake,
  54 * assuming only 4 bits for a mac address and for BSSIDs you can then have:
  55 *
  56 *                  \
  57 * MAC:        0001 |
  58 * BSSID-01:   0100 | --> Belongs to us
  59 * BSSID-02:   1001 |
  60 *                  /
  61 * -------------------
  62 * BSSID-03:   0110  | --> External
  63 * -------------------
  64 *
  65 * Our bssid_mask would then be:
  66 *
  67 *             On loop iteration for BSSID-01:
  68 *             ~(0001 ^ 0100)  -> ~(0101)
  69 *                             ->   1010
  70 *             bssid_mask      =    1010
  71 *
  72 *             On loop iteration for BSSID-02:
  73 *             bssid_mask &= ~(0001   ^   1001)
  74 *             bssid_mask =   (1010)  & ~(0001 ^ 1001)
  75 *             bssid_mask =   (1010)  & ~(1000)
  76 *             bssid_mask =   (1010)  &  (0111)
  77 *             bssid_mask =   0010
  78 *
  79 * A bssid_mask of 0010 means "only pay attention to the second least
  80 * significant bit". This is because its the only bit common
  81 * amongst the MAC and all BSSIDs we support. To findout what the real
  82 * common bit is we can simply "&" the bssid_mask now with any BSSID we have
  83 * or our MAC address (we assume the hardware uses the MAC address).
  84 *
  85 * Now, suppose there's an incoming frame for BSSID-03:
  86 *
  87 * IFRAME-01:  0110
  88 *
  89 * An easy eye-inspeciton of this already should tell you that this frame
  90 * will not pass our check. This is because the bssid_mask tells the
  91 * hardware to only look at the second least significant bit and the
  92 * common bit amongst the MAC and BSSIDs is 0, this frame has the 2nd LSB
  93 * as 1, which does not match 0.
  94 *
  95 * So with IFRAME-01 we *assume* the hardware will do:
  96 *
  97 *     allow = (IFRAME-01 & bssid_mask) == (bssid_mask & MAC) ? 1 : 0;
  98 *  --> allow = (0110 & 0010) == (0010 & 0001) ? 1 : 0;
  99 *  --> allow = (0010) == 0000 ? 1 : 0;
 100 *  --> allow = 0
 101 *
 102 *  Lets now test a frame that should work:
 103 *
 104 * IFRAME-02:  0001 (we should allow)
 105 *
 106 *     allow = (IFRAME-02 & bssid_mask) == (bssid_mask & MAC) ? 1 : 0;
 107 *  --> allow = (0001 & 0010) ==  (0010 & 0001) ? 1 :0;
 108 *  --> allow = (0000) == (0000)
 109 *  --> allow = 1
 110 *
 111 * Other examples:
 112 *
 113 * IFRAME-03:  0100 --> allowed
 114 * IFRAME-04:  1001 --> allowed
 115 * IFRAME-05:  1101 --> allowed but its not for us!!!
 116 *
 117 */
 118void ath_hw_setbssidmask(struct ath_common *common)
 119{
 120        void *ah = common->ah;
 121        u32 id1;
 122
 123        REG_WRITE(ah, AR_STA_ID0, get_unaligned_le32(common->macaddr));
 124        id1 = REG_READ(ah, AR_STA_ID1) & ~AR_STA_ID1_SADH_MASK;
 125        id1 |= get_unaligned_le16(common->macaddr + 4);
 126        REG_WRITE(ah, AR_STA_ID1, id1);
 127
 128        REG_WRITE(ah, AR_BSSMSKL, get_unaligned_le32(common->bssidmask));
 129        REG_WRITE(ah, AR_BSSMSKU, get_unaligned_le16(common->bssidmask + 4));
 130}
 131EXPORT_SYMBOL(ath_hw_setbssidmask);
 132
 133
 134/**
 135 * ath_hw_cycle_counters_update - common function to update cycle counters
 136 *
 137 * @common: the ath_common struct for the device.
 138 *
 139 * This function is used to update all cycle counters in one place.
 140 * It has to be called while holding common->cc_lock!
 141 */
 142void ath_hw_cycle_counters_update(struct ath_common *common)
 143{
 144        u32 cycles, busy, rx, tx;
 145        void *ah = common->ah;
 146
 147        /* freeze */
 148        REG_WRITE(ah, AR_MIBC, AR_MIBC_FMC);
 149
 150        /* read */
 151        cycles = REG_READ(ah, AR_CCCNT);
 152        busy = REG_READ(ah, AR_RCCNT);
 153        rx = REG_READ(ah, AR_RFCNT);
 154        tx = REG_READ(ah, AR_TFCNT);
 155
 156        /* clear */
 157        REG_WRITE(ah, AR_CCCNT, 0);
 158        REG_WRITE(ah, AR_RFCNT, 0);
 159        REG_WRITE(ah, AR_RCCNT, 0);
 160        REG_WRITE(ah, AR_TFCNT, 0);
 161
 162        /* unfreeze */
 163        REG_WRITE(ah, AR_MIBC, 0);
 164
 165        /* update all cycle counters here */
 166        common->cc_ani.cycles += cycles;
 167        common->cc_ani.rx_busy += busy;
 168        common->cc_ani.rx_frame += rx;
 169        common->cc_ani.tx_frame += tx;
 170
 171        common->cc_survey.cycles += cycles;
 172        common->cc_survey.rx_busy += busy;
 173        common->cc_survey.rx_frame += rx;
 174        common->cc_survey.tx_frame += tx;
 175}
 176EXPORT_SYMBOL(ath_hw_cycle_counters_update);
 177
 178int32_t ath_hw_get_listen_time(struct ath_common *common)
 179{
 180        struct ath_cycle_counters *cc = &common->cc_ani;
 181        int32_t listen_time;
 182
 183        listen_time = (cc->cycles - cc->rx_frame - cc->tx_frame) /
 184                      (common->clockrate * 1000);
 185
 186        memset(cc, 0, sizeof(*cc));
 187
 188        return listen_time;
 189}
 190EXPORT_SYMBOL(ath_hw_get_listen_time);
 191
Hosted by Missing Link Electronics. The original LXR software by the LXR community, this experimental version by lxr@linux.no.