package/kernel/mac80211/patches/305-ath5k-channel-change-fix.patch

   1 From: Sergey Ryazanov <ryazanov.s.a@gmail.com>
   2 Date: Wed, 4 Mar 2015 05:12:10 +0300
   3 Subject: [PATCH] ath5k: channel change fix
   4
   5 ath5k updates the channel pointer and after that it stops the Rx logic
   6 and apply channel to HW. In case of channel switch, such sequence
   7 creates a small window when a frame, which is received on the old
   8 channel is considered as a frame received on the new one.
   9
  10 The most notable consequence of this situation occurs during the switch
  11 from 2 GHz band (CCK+OFDM) to the 5GHz band (OFDM-only). Frame received
  12 with CCK rate, e.g. beacon received at the 1mbps, causes the following
  13 warning:
  14
  15   WARNING: at ath5k/base.c:589 ath5k_tasklet_rx+0x318/0x6ec [ath5k]()
  16   invalid hw_rix: 1a
  17   [..]
  18   Call Trace:
  19   [<802656a8>] show_stack+0x48/0x70
  20   [<802dd92c>] warn_slowpath_common+0x88/0xbc
  21   [<802dd98c>] warn_slowpath_fmt+0x2c/0x38
  22   [<81b51be8>] ath5k_tasklet_rx+0x318/0x6ec [ath5k]
  23   [<8028ac64>] tasklet_action+0x8c/0xf0
  24   [<80075804>] __do_softirq+0x180/0x32c
  25   [<80196ce8>] irq_exit+0x54/0x70
  26   [<80041848>] ret_from_irq+0x0/0x4
  27   [<80182fdc>] ioread32+0x4/0xc
  28   [<81b4c42c>] ath5k_hw_set_sleep_clock+0x2ec/0x474 [ath5k]
  29   [<81b4cf28>] ath5k_hw_reset+0x50/0xeb8 [ath5k]
  30   [<81b50900>] ath5k_reset+0xd4/0x310 [ath5k]
  31   [<81b557e8>] ath5k_config+0x4c/0x104 [ath5k]
  32   [<80d01770>] ieee80211_hw_config+0x2f4/0x35c [mac80211]
  33   [<80d09aa8>] ieee80211_scan_work+0x2e4/0x414 [mac80211]
  34   [<8022c3f4>] process_one_work+0x28c/0x400
  35   [<802df8f8>] worker_thread+0x258/0x3c0
  36   [<801b5710>] kthread+0xe0/0xec
  37   [<800418a8>] ret_from_kernel_thread+0x14/0x1c
  38
  39 The easiest way to reproduce this warning is to run scan with dualband
  40 NIC in noisy environments, when the channel 11 runs multiple APs. In my
  41 tests if the APs num >= 12, the warning appears in the first few
  42 seconds of scanning.
  43
  44 In order to fix this, the Rx disable code moved to a higher level and
  45 placed before the channel pointer update. This is also makes the code a
  46 bit more symmetrical, since we disable and enable the Rx in the same
  47 function.
  48
  49 In fact, at the pointer update time new frames should not appear,
  50 because interrupt generation at this point should already be disabled.
  51 The next patch should address this issue.
  52
  53 CC: Jiri Slaby <jirislaby@gmail.com>
  54 CC: Nick Kossifidis <mickflemm@gmail.com>
  55 CC: Luis R. Rodriguez <mcgrof@do-not-panic.com>
  56 Reported-by: Christophe Prevotaux <cprevotaux@nltinc.com>
  57 Tested-by: Christophe Prevotaux <cprevotaux@nltinc.com>
  58 Tested-by: Eric Bree <ebree@nltinc.com>
  59 Signed-off-by: Sergey Ryazanov <ryazanov.s.a@gmail.com>
  60 ---
  61
  62 --- a/drivers/net/wireless/ath/ath5k/base.c
  63 +++ b/drivers/net/wireless/ath/ath5k/base.c
  64 @@ -2858,7 +2858,7 @@ ath5k_reset(struct ath5k_hw *ah, struct
  65  {
  66         struct ath_common *common = ath5k_hw_common(ah);
  67         int ret, ani_mode;
  68 -       bool fast;
  69 +       bool fast = chan && modparam_fastchanswitch ? 1 : 0;
  70
  71         ATH5K_DBG(ah, ATH5K_DEBUG_RESET, "resetting\n");
  72
  73 @@ -2876,11 +2876,29 @@ ath5k_reset(struct ath5k_hw *ah, struct
  74          * so we should also free any remaining
  75          * tx buffers */
  76         ath5k_drain_tx_buffs(ah);
  77 +
  78 +       /* Stop PCU */
  79 +       ath5k_hw_stop_rx_pcu(ah);
  80 +
  81 +       /* Stop DMA
  82 +        *
  83 +        * Note: If DMA didn't stop continue
  84 +        * since only a reset will fix it.
  85 +        */
  86 +       ret = ath5k_hw_dma_stop(ah);
  87 +
  88 +       /* RF Bus grant won't work if we have pending
  89 +        * frames
  90 +        */
  91 +       if (ret && fast) {
  92 +               ATH5K_DBG(ah, ATH5K_DEBUG_RESET,
  93 +                         "DMA didn't stop, falling back to normal reset\n");
  94 +               fast = false;
  95 +       }
  96 +
  97         if (chan)
  98                 ah->curchan = chan;
  99
 100 -       fast = ((chan != NULL) && modparam_fastchanswitch) ? 1 : 0;
 101 -
 102         ret = ath5k_hw_reset(ah, ah->opmode, ah->curchan, fast, skip_pcu);
 103         if (ret) {
 104                 ATH5K_ERR(ah, "can't reset hardware (%d)\n", ret);
 105 --- a/drivers/net/wireless/ath/ath5k/reset.c
 106 +++ b/drivers/net/wireless/ath/ath5k/reset.c
 107 @@ -1169,30 +1169,6 @@ ath5k_hw_reset(struct ath5k_hw *ah, enum
 108         if (ah->ah_version == AR5K_AR5212)
 109                 ath5k_hw_set_sleep_clock(ah, false);
 110
 111 -       /*
 112 -        * Stop PCU
 113 -        */
 114 -       ath5k_hw_stop_rx_pcu(ah);
 115 -
 116 -       /*
 117 -        * Stop DMA
 118 -        *
 119 -        * Note: If DMA didn't stop continue
 120 -        * since only a reset will fix it.
 121 -        */
 122 -       ret = ath5k_hw_dma_stop(ah);
 123 -
 124 -       /* RF Bus grant won't work if we have pending
 125 -        * frames */
 126 -       if (ret && fast) {
 127 -               ATH5K_DBG(ah, ATH5K_DEBUG_RESET,
 128 -                       "DMA didn't stop, falling back to normal reset\n");
 129 -               fast = false;
 130 -               /* Non fatal, just continue with
 131 -                * normal reset */
 132 -               ret = 0;
 133 -       }
 134 -
 135         mode = channel->hw_value;
 136         switch (mode) {
 137         case AR5K_MODE_11A: