On 11/21/2016 04:10 PM, Michal Kazior wrote:
> On 21 November 2016 at 15:41, Zefir Kurtisi <zefir.kurtisi@xxxxxxxxxxx> wrote:
>> On 11/21/2016 03:04 PM, Benjamin Berg wrote:
>>> In the case that a spectral scan is enabled the PHY errors sent by the
>>> hardware as part of the scanning might trigger the radar detection and
>>> channels might be marked as 'unusable' incorrectly. This patch fixes
>>> the issue by preventing the spectral scan to be enabled if DFS is used
>>> and only analysing the PHY errors for DFS if radar detection is enabled.
>>>
>>> [...]
>>
>> From the relevant source code portion in channel.c:ath_set_channel()
>>
>> 80 /* Enable radar pulse detection if on a DFS channel. Spectral
>> 81 * scanning and radar detection can not be used concurrently.
>> 82 */
>> 83 if (hw->conf.radar_enabled) {
>> 84 u32 rxfilter;
>> 85
>> 86 rxfilter = ath9k_hw_getrxfilter(ah);
>> 87 rxfilter |= ATH9K_RX_FILTER_PHYRADAR |
>> 88 ATH9K_RX_FILTER_PHYERR;
>> 89 ath9k_hw_setrxfilter(ah, rxfilter);
>> 90 ath_dbg(common, DFS, "DFS enabled at freq %d\n",
>> 91 chan->center_freq);
>> 92 } else {
>> 93 /* perform spectral scan if requested. */
>> 94 if (test_bit(ATH_OP_SCANNING, &common->op_flags) &&
>> 95 sc->spec_priv.spectral_mode == SPECTRAL_CHANSCAN)
>> 96 ath9k_cmn_spectral_scan_trigger(common, &sc->spec_priv);
>> 97 }
>>
>> it seems that spectral can't ever be activated while operating on a DFS channel.
>>
>> If you need to catch the opposite case, i.e. prevent feeding pseudo-radar pulses
>> into the pattern detector, you just need to ensure that they depend on
>> hw->conf.radar_enabled. A patch like the attached one should be enough.
>
> Good point. I guess set_channel could be oversimplified as well. I
> mean, it makes sense to consider radar and spectral mutually exclusive
> if they use the same phyerr code. However some chips actually seem (as
> per the comment I mentioned) to distinguish the two so I don't know if
> the "mutually exclusive" is true for all chips per se. Just thinking
> out loud.
>
You're right, blindly feeding PHYERR frames to spectral when spectral is not
enabled is as wrong as feeding them to the dfs-detector when not on a radar
channel. Therefore, the patch I proposed should be extended to make calling
ath_cmn_process_fft() depending on
a) not operating on radar channel, and
b) spectral scan is enabled
Updated patch attached as proposal.
> I also wonder if calling ieee80211_radar_detect() should have any
> effect if there are no radar operated interfaces in the first place?
>
True, calling ieee80211_radar_detect() for a non-DFS channel is (or should be)
ignored by mac. But feeding the dfs-detector with invalid pulses causes quite some
computational overhead - dropping them if no radar detection is required is a good
thing to do.
Cheers,
Zefir
>From aaa28dcaf0879c6bfc7be96077c79894bb230dfb Mon Sep 17 00:00:00 2001
From: Zefir Kurtisi <zefir.kurtisi@xxxxxxxxxxx>
Date: Mon, 21 Nov 2016 15:33:45 +0100
Subject: [PATCH] ath9k: feed DFS detector only if operating on radar channel
---
drivers/net/wireless/ath/ath9k/recv.c | 17 ++++++++++++++---
1 file changed, 14 insertions(+), 3 deletions(-)
diff --git a/drivers/net/wireless/ath/ath9k/recv.c b/drivers/net/wireless/ath/ath9k/recv.c
index 6697342..48f8af1 100644
--- a/drivers/net/wireless/ath/ath9k/recv.c
+++ b/drivers/net/wireless/ath/ath9k/recv.c
@@ -867,10 +867,21 @@ static int ath9k_rx_skb_preprocess(struct ath_softc *sc,
* can be dropped.
*/
if (rx_stats->rs_status & ATH9K_RXERR_PHY) {
- ath9k_dfs_process_phyerr(sc, hdr, rx_stats, rx_status->mactime);
- if (ath_cmn_process_fft(&sc->spec_priv, hdr, rx_stats, rx_status->mactime))
+ /*
+ * DFS and spectral are mutually exclusive
+ *
+ * Since some chips use RXERR_PHY as indication for both, we
+ * need to double check which feature is enabled to prevent
+ * feeding spectral or dfs-detector with wrong frames.
+ */
+ if (hw->conf.radar_enabled) {
+ ath9k_dfs_process_phyerr(sc, hdr, rx_stats,
+ rx_status->mactime);
+ } else if (sc->spec_priv.spectral_mode != SPECTRAL_DISABLED &&
+ ath_cmn_process_fft(&sc->spec_priv, hdr, rx_stats,
+ rx_status->mactime)) {
RX_STAT_INC(rx_spectral);
-
+ }
return -EINVAL;
}
--
2.7.4
