Return-path: Received: from mail.neratec.com ([46.140.151.2]:64204 "EHLO mail.neratec.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932262AbcKUQQv (ORCPT ); Mon, 21 Nov 2016 11:16:51 -0500 Subject: Re: [ath9k-devel] [PATCH] ath9k: Prevent radar detection and spectral scan to be used concurrently To: Michal Kazior References: <20161121140423.24367-1-benjamin@sipsolutions.net> <7d04126f-0f24-b4a4-6d13-6f52046d7671@neratec.com> Cc: Benjamin Berg , Kalle Valo , "ath9k-devel@lists.ath9k.org" , linux-wireless From: Zefir Kurtisi Message-ID: (sfid-20161121_171703_170422_8DD67438) Date: Mon, 21 Nov 2016 17:16:42 +0100 MIME-Version: 1.0 In-Reply-To: Content-Type: multipart/mixed; boundary="------------11A569B53BEACB1640D79D21" Sender: linux-wireless-owner@vger.kernel.org List-ID: This is a multi-part message in MIME format. --------------11A569B53BEACB1640D79D21 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit On 11/21/2016 04:10 PM, Michal Kazior wrote: > On 21 November 2016 at 15:41, Zefir Kurtisi 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 --------------11A569B53BEACB1640D79D21 Content-Type: text/x-patch; name="0001-ath9k-feed-DFS-detector-only-if-operating-on-radar-c.patch" Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename*0="0001-ath9k-feed-DFS-detector-only-if-operating-on-radar-c.pa"; filename*1="tch" >From aaa28dcaf0879c6bfc7be96077c79894bb230dfb Mon Sep 17 00:00:00 2001 From: Zefir Kurtisi 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 --------------11A569B53BEACB1640D79D21--