mac80211: ath9k: Add RX inactivity detection and reset chip
Some ath9k chips can, seemingly at random, end up in a state which can be described as "deaf". No or nearly no interrupts are generated anymore for incoming packets. Existing links either break down after a while and new links will not be established. This is merged upstream in https://patchwork.kernel.org/project/linux-wireless/patch/20241106-ath9k-deaf-detection-v1-1-736a150d2425@redhat.com/ Signed-off-by: Florian Maurer <f.maurer@outlook.de> Link: https://github.com/openwrt/openwrt/pull/21487 Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
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Florian Maurer
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Hauke Mehrtens
Hauke Mehrtens
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From: =?utf-8?q?Toke_H=C3=B8iland-J=C3=B8rgensen?= <toke@toke.dk>
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Date: Wed, 06 Nov 2024 13:41:44 +0100
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Subject: [PATCH] ath9k: Add RX inactivity detection and reset chip when it
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occurs
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Some ath9k chips can, seemingly at random, end up in a state which can
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be described as "deaf". No or nearly no interrupts are generated anymore
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for incoming packets. Existing links either break down after a while and
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new links will not be established.
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The circumstances leading to this "deafness" is still unclear, but some
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particular chips (especially 2-stream 11n SoCs, but also others) can go
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'deaf' when running AP or mesh (or both) after some time. It's probably
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a hardware issue, and doing a channel scan to trigger a chip
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reset (which one normally can't do on an AP interface) recovers the
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hardware.
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The only way the driver can detect this state, is by detecting if there
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has been no RX activity for a while. In this case we can proactively
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reset the chip (which only takes a small number of milliseconds, so
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shouldn't interrupt things too much if it has been idle for several
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seconds), which functions as a workaround.
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OpenWrt, and various derivatives, have been carrying versions of this
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workaround for years, that were never upstreamed. One version[0],
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written by Felix Fietkau, used a simple counter and only reset if there
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was precisely zero RX activity for a long period of time. This had the
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problem that in some cases a small number of interrupts would appear
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even if the device was otherwise not responsive. For this reason,
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another version[1], written by Simon Wunderlich and Sven Eckelmann, used
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a time-based approach to calculate the average number of RX interrupts
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over a longer (four-second) interval, and reset the chip when seeing
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less than one interrupt per second over this period. However, that
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version relied on debugfs counters to keep track of the number of
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interrupts, which means it didn't work at all if debugfs was not
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enabled.
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This patch unifies the two versions: it uses the same approach as Felix'
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patch to count the number of RX handler invocations, but uses the same
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time-based windowing approach as Simon and Sven's patch to still handle
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the case where occasional interrupts appear but the device is otherwise
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deaf.
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Since this is based on ideas by all three people, but not actually
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directly derived from any of the patches, I'm including Suggested-by
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tags from Simon, Sven and Felix below, which should hopefully serve as
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proper credit.
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[0] https://patchwork.kernel.org/project/linux-wireless/patch/20170125163654.66431-3-nbd@nbd.name/
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[1] https://patchwork.kernel.org/project/linux-wireless/patch/20161117083614.19188-2-sven.eckelmann@open-mesh.com/
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Suggested-by: Simon Wunderlich <sw@simonwunderlich.de>
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Suggested-by: Sven Eckelmann <se@simonwunderlich.de>
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Suggested-by: Felix Fietkau <nbd@nbd.name>
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Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk>
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Reviewed-by: Sven Eckelmann <se@simonwunderlich.de>
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Acked-by: Simon Wunderlich <sw@simonwunderlich.de>
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Tested-by: Issam Hamdi <ih@simonwunderlich.de>
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Tested-by: Sven Eckelmann <se@simonwunderlich.de>
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---
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drivers/net/wireless/ath/ath9k/ath9k.h | 2 ++
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drivers/net/wireless/ath/ath9k/debug.c | 1 +
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drivers/net/wireless/ath/ath9k/debug.h | 1 +
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drivers/net/wireless/ath/ath9k/link.c | 33 +++++++++++++++++++++++++++++++--
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drivers/net/wireless/ath/ath9k/main.c | 1 +
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5 files changed, 36 insertions(+), 2 deletions(-)
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---
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base-commit: c33f9c2728d0ccc7472e6239346c0fb3de556e0f
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change-id: 20241105-ath9k-deaf-detection-0e26bb3243a6
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--- a/drivers/net/wireless/ath/ath9k/ath9k.h
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+++ b/drivers/net/wireless/ath/ath9k/ath9k.h
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@@ -1041,6 +1041,8 @@ struct ath_softc {
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u8 gtt_cnt;
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u32 intrstatus;
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+ u32 rx_active_check_time;
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+ u32 rx_active_count;
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u16 ps_flags; /* PS_* */
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bool ps_enabled;
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bool ps_idle;
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--- a/drivers/net/wireless/ath/ath9k/debug.c
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+++ b/drivers/net/wireless/ath/ath9k/debug.c
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@@ -805,6 +805,7 @@ static int read_file_reset(struct seq_fi
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[RESET_TYPE_CALIBRATION] = "Calibration error",
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[RESET_TX_DMA_ERROR] = "Tx DMA stop error",
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[RESET_RX_DMA_ERROR] = "Rx DMA stop error",
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+ [RESET_TYPE_RX_INACTIVE] = "Rx path inactive",
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};
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int i;
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--- a/drivers/net/wireless/ath/ath9k/debug.h
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+++ b/drivers/net/wireless/ath/ath9k/debug.h
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@@ -53,6 +53,7 @@ enum ath_reset_type {
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RESET_TYPE_CALIBRATION,
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RESET_TX_DMA_ERROR,
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RESET_RX_DMA_ERROR,
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+ RESET_TYPE_RX_INACTIVE,
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__RESET_TYPE_MAX
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};
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--- a/drivers/net/wireless/ath/ath9k/link.c
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+++ b/drivers/net/wireless/ath/ath9k/link.c
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@@ -50,7 +50,36 @@ reset:
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"tx hung, resetting the chip\n");
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ath9k_queue_reset(sc, RESET_TYPE_TX_HANG);
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return false;
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+}
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+
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+#define RX_INACTIVE_CHECK_INTERVAL (4 * MSEC_PER_SEC)
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+
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+static bool ath_hw_rx_inactive_check(struct ath_softc *sc)
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+{
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+ struct ath_common *common = ath9k_hw_common(sc->sc_ah);
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+ u32 interval, count;
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+
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+ interval = jiffies_to_msecs(jiffies - sc->rx_active_check_time);
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+ count = sc->rx_active_count;
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+ if (interval < RX_INACTIVE_CHECK_INTERVAL)
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+ return true; /* too soon to check */
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+
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+ sc->rx_active_count = 0;
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+ sc->rx_active_check_time = jiffies;
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+
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+ /* Need at least one interrupt per second, and we should only react if
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+ * we are within a factor two of the expected interval
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+ */
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+ if (interval > RX_INACTIVE_CHECK_INTERVAL * 2 ||
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+ count >= interval / MSEC_PER_SEC)
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+ return true;
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+
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+ ath_dbg(common, RESET,
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+ "RX inactivity detected. Schedule chip reset\n");
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+ ath9k_queue_reset(sc, RESET_TYPE_RX_INACTIVE);
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+
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+ return false;
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}
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void ath_hw_check_work(struct work_struct *work)
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@@ -58,8 +87,8 @@ void ath_hw_check_work(struct work_struc
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struct ath_softc *sc = container_of(work, struct ath_softc,
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hw_check_work.work);
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- if (!ath_hw_check(sc) ||
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- !ath_tx_complete_check(sc))
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+ if (!ath_hw_check(sc) || !ath_tx_complete_check(sc) ||
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+ !ath_hw_rx_inactive_check(sc))
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return;
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ieee80211_queue_delayed_work(sc->hw, &sc->hw_check_work,
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--- a/drivers/net/wireless/ath/ath9k/main.c
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+++ b/drivers/net/wireless/ath/ath9k/main.c
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@@ -454,6 +454,7 @@ void ath9k_tasklet(struct tasklet_struct
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ath_rx_tasklet(sc, 0, true);
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ath_rx_tasklet(sc, 0, false);
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+ sc->rx_active_count++;
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}
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if (status & ATH9K_INT_TX) {
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