The following series adds a check for a hardware condition which can cause
an unwanted ATIM window configuration and some other smaller improvements for
TSF related things.
---
Bruno Randolf (4):
ath5k: Remove unused variable for atim window
ath5k: Check and fix ATIM window
ath5k: Increase "fudge" for beacon timers
ath5k: Disable interrupts in ath5k_hw_get_tsf64
drivers/net/wireless/ath/ath5k/ath5k.h | 2 -
drivers/net/wireless/ath/ath5k/attach.c | 1
drivers/net/wireless/ath/ath5k/base.c | 16 ++++-
drivers/net/wireless/ath/ath5k/pcu.c | 99 +++++++++++++++++++++++++++++++
4 files changed, 113 insertions(+), 5 deletions(-)
--
Signature
We use FUDGE to make sure the next TBTT is ahead of the current TU.
Since we later substract AR5K_TUNE_SW_BEACON_RESP (10) in the timer
configuration we need to make sure it is bigger than that.
Signed-off-by: Bruno Randolf <[email protected]>
---
drivers/net/wireless/ath/ath5k/base.c | 7 +++++--
1 files changed, 5 insertions(+), 2 deletions(-)
diff --git a/drivers/net/wireless/ath/ath5k/base.c b/drivers/net/wireless/ath/ath5k/base.c
index 4103765..94cc335 100644
--- a/drivers/net/wireless/ath/ath5k/base.c
+++ b/drivers/net/wireless/ath/ath5k/base.c
@@ -1886,8 +1886,11 @@ ath5k_beacon_update_timers(struct ath5k_softc *sc, u64 bc_tsf)
hw_tsf = ath5k_hw_get_tsf64(ah);
hw_tu = TSF_TO_TU(hw_tsf);
-#define FUDGE 3
- /* we use FUDGE to make sure the next TBTT is ahead of the current TU */
+#define FUDGE AR5K_TUNE_SW_BEACON_RESP + 3
+ /* We use FUDGE to make sure the next TBTT is ahead of the current TU.
+ * Since we later substract AR5K_TUNE_SW_BEACON_RESP (10) in the timer
+ * configuration we need to make sure it is bigger than that. */
+
if (bc_tsf == -1) {
/*
* no beacons received, called internally.
The code in ath5k_hw_get_tsf64() is time critical and will return wrong results
if we get interrupted, so disable local interrupts.
Signed-off-by: Bruno Randolf <[email protected]>
---
drivers/net/wireless/ath/ath5k/pcu.c | 6 ++++++
1 files changed, 6 insertions(+), 0 deletions(-)
diff --git a/drivers/net/wireless/ath/ath5k/pcu.c b/drivers/net/wireless/ath/ath5k/pcu.c
index 604114f..095d30b 100644
--- a/drivers/net/wireless/ath/ath5k/pcu.c
+++ b/drivers/net/wireless/ath/ath5k/pcu.c
@@ -495,6 +495,10 @@ u64 ath5k_hw_get_tsf64(struct ath5k_hw *ah)
{
u32 tsf_lower, tsf_upper1, tsf_upper2;
int i;
+ unsigned long flags;
+
+ /* This code is time critical - we don't want to be interrupted here */
+ local_irq_save(flags);
/*
* While reading TSF upper and then lower part, the clock is still
@@ -517,6 +521,8 @@ u64 ath5k_hw_get_tsf64(struct ath5k_hw *ah)
tsf_upper1 = tsf_upper2;
}
+ local_irq_restore(flags);
+
WARN_ON( i == ATH5K_MAX_TSF_READ );
return (((u64)tsf_upper1 << 32) | tsf_lower);
It's not used and it's unlikely we will ever implement ATIM.
Signed-off-by: Bruno Randolf <[email protected]>
---
drivers/net/wireless/ath/ath5k/ath5k.h | 1 -
drivers/net/wireless/ath/ath5k/attach.c | 1 -
drivers/net/wireless/ath/ath5k/pcu.c | 2 +-
3 files changed, 1 insertions(+), 3 deletions(-)
diff --git a/drivers/net/wireless/ath/ath5k/ath5k.h b/drivers/net/wireless/ath/ath5k/ath5k.h
index b96bb98..42e6e82 100644
--- a/drivers/net/wireless/ath/ath5k/ath5k.h
+++ b/drivers/net/wireless/ath/ath5k/ath5k.h
@@ -1041,7 +1041,6 @@ struct ath5k_hw {
#define ah_modes ah_capabilities.cap_mode
#define ah_ee_version ah_capabilities.cap_eeprom.ee_version
- u32 ah_atim_window;
u32 ah_limit_tx_retries;
u8 ah_coverage_class;
diff --git a/drivers/net/wireless/ath/ath5k/attach.c b/drivers/net/wireless/ath/ath5k/attach.c
index 6e02de3..cd0b14a 100644
--- a/drivers/net/wireless/ath/ath5k/attach.c
+++ b/drivers/net/wireless/ath/ath5k/attach.c
@@ -118,7 +118,6 @@ int ath5k_hw_attach(struct ath5k_softc *sc)
ah->ah_turbo = false;
ah->ah_txpower.txp_tpc = AR5K_TUNE_TPC_TXPOWER;
ah->ah_imr = 0;
- ah->ah_atim_window = 0;
ah->ah_limit_tx_retries = AR5K_INIT_TX_RETRY;
ah->ah_software_retry = false;
ah->ah_ant_mode = AR5K_ANTMODE_DEFAULT;
diff --git a/drivers/net/wireless/ath/ath5k/pcu.c b/drivers/net/wireless/ath/ath5k/pcu.c
index 6a891c4..71dca10 100644
--- a/drivers/net/wireless/ath/ath5k/pcu.c
+++ b/drivers/net/wireless/ath/ath5k/pcu.c
@@ -600,7 +600,7 @@ void ath5k_hw_init_beacon(struct ath5k_hw *ah, u32 next_beacon, u32 interval)
/* Timer3 marks the end of our ATIM window
* a zero length window is not allowed because
* we 'll get no beacons */
- timer3 = next_beacon + (ah->ah_atim_window ? ah->ah_atim_window : 1);
+ timer3 = next_beacon + 1;
/*
* Set the beacon register and enable all timers.
This patch adds sanity-checks for the beacon timers and especially the ATIM
window to ath5k. It is basically the same what i did for madwifi two years ago
and fixes a problem in IBSS mode which has been described as "ramping" pings.
See the code comments for a more detailed description and these links:
http://madwifi-project.org/ticket/1154
http://madwifi-project.org/changeset/3867
http://thread.gmane.org/gmane.linux.drivers.madwifi.devel/6066
Signed-off-by: Bruno Randolf <[email protected]>
---
drivers/net/wireless/ath/ath5k/ath5k.h | 1
drivers/net/wireless/ath/ath5k/base.c | 9 +++
drivers/net/wireless/ath/ath5k/pcu.c | 91 ++++++++++++++++++++++++++++++++
3 files changed, 101 insertions(+), 0 deletions(-)
diff --git a/drivers/net/wireless/ath/ath5k/ath5k.h b/drivers/net/wireless/ath/ath5k/ath5k.h
index 42e6e82..0cba2e3 100644
--- a/drivers/net/wireless/ath/ath5k/ath5k.h
+++ b/drivers/net/wireless/ath/ath5k/ath5k.h
@@ -1195,6 +1195,7 @@ u64 ath5k_hw_get_tsf64(struct ath5k_hw *ah);
void ath5k_hw_set_tsf64(struct ath5k_hw *ah, u64 tsf64);
void ath5k_hw_reset_tsf(struct ath5k_hw *ah);
void ath5k_hw_init_beacon(struct ath5k_hw *ah, u32 next_beacon, u32 interval);
+bool ath5k_hw_check_beacon_timers(struct ath5k_hw *ah, int intval);
/* ACK bit rate */
void ath5k_hw_set_ack_bitrate_high(struct ath5k_hw *ah, bool high);
/* Clock rate related functions */
diff --git a/drivers/net/wireless/ath/ath5k/base.c b/drivers/net/wireless/ath/ath5k/base.c
index 95072db..4103765 100644
--- a/drivers/net/wireless/ath/ath5k/base.c
+++ b/drivers/net/wireless/ath/ath5k/base.c
@@ -1191,6 +1191,15 @@ ath5k_check_ibss_tsf(struct ath5k_softc *sc, struct sk_buff *skb,
*/
if (hw_tu >= sc->nexttbtt)
ath5k_beacon_update_timers(sc, bc_tstamp);
+
+ /* Check if the beacon timers are still correct, because a TSF
+ * update might have created a window between them - for a
+ * longer description see the comment of this function: */
+ if (!ath5k_hw_check_beacon_timers(sc->ah, sc->bintval)) {
+ ath5k_beacon_update_timers(sc, bc_tstamp);
+ ATH5K_DBG_UNLIMIT(sc, ATH5K_DEBUG_BEACON,
+ "fixed beacon timers after beacon receive\n");
+ }
}
}
diff --git a/drivers/net/wireless/ath/ath5k/pcu.c b/drivers/net/wireless/ath/ath5k/pcu.c
index 71dca10..604114f 100644
--- a/drivers/net/wireless/ath/ath5k/pcu.c
+++ b/drivers/net/wireless/ath/ath5k/pcu.c
@@ -641,6 +641,97 @@ void ath5k_hw_init_beacon(struct ath5k_hw *ah, u32 next_beacon, u32 interval)
}
/**
+ * ath5k_check_timer_win - Check if timer B is timer A + window
+ *
+ * @a: timer a (before b)
+ * @b: timer b (after a)
+ * @window: difference between a and b
+ * @intval: timers are increased by this interval
+ *
+ * This helper function checks if timer B is timer A + window and covers
+ * cases where timer A or B might have already been updated or wrapped
+ * around (Timers are 16 bit).
+ *
+ * Returns true if O.K.
+ */
+static inline bool
+ath5k_check_timer_win(int a, int b, int window, int intval)
+{
+ /*
+ * 1.) usually B should be A + window
+ * 2.) A already updated, B not updated yet
+ * 3.) A already updated and has wrapped around
+ * 4.) B has wrapped around
+ */
+ if ((b - a == window) || /* 1.) */
+ (a - b == intval - window) || /* 2.) */
+ ((a | 0x10000) - b == intval - window) || /* 3.) */
+ ((b | 0x10000) - a == window)) /* 4.) */
+ return true; /* O.K. */
+ return false;
+}
+
+/**
+ * ath5k_hw_check_beacon_timers - Check if the beacon timers are correct
+ *
+ * @ah: The &struct ath5k_hw
+ * @intval: beacon interval
+ *
+ * This is a workaround for IBSS mode:
+ *
+ * The need for this function arises from the fact that we have 4 separate
+ * HW timer registers (TIMER0 - TIMER3), which are closely related to the
+ * next beacon target time (NBTT), and that the HW updates these timers
+ * seperately based on the current TSF value. The hardware increments each
+ * timer by the beacon interval, when the local TSF coverted to TU is equal
+ * to the value stored in the timer.
+ *
+ * The reception of a beacon with the same BSSID can update the local HW TSF
+ * at any time - this is something we can't avoid. If the TSF jumps to a
+ * time which is later than the time stored in a timer, this timer will not
+ * be updated until the TSF in TU wraps around at 16 bit (the size of the
+ * timers) and reaches the time which is stored in the timer.
+ *
+ * The problem is that these timers are closely related to TIMER0 (NBTT) and
+ * that they define a time "window". When the TSF jumps between two timers
+ * (e.g. ATIM and NBTT), the one in the past will be left behind (not
+ * updated), while the one in the future will be updated every beacon
+ * interval. This causes the window to get larger, until the TSF wraps
+ * around as described above and the timer which was left behind gets
+ * updated again. But - because the beacon interval is usually not an exact
+ * divisor of the size of the timers (16 bit), an unwanted "window" between
+ * these timers has developed!
+ *
+ * This is especially important with the ATIM window, because during
+ * the ATIM window only ATIM frames and no data frames are allowed to be
+ * sent, which creates transmission pauses after each beacon. This symptom
+ * has been described as "ramping ping" because ping times increase linearly
+ * for some time and then drop down again. A wrong window on the DMA beacon
+ * timer has the same effect, so we check for these two conditions.
+ *
+ * Returns true if O.K.
+ */
+bool
+ath5k_hw_check_beacon_timers(struct ath5k_hw *ah, int intval)
+{
+ unsigned int nbtt, atim, dma;
+
+ nbtt = ath5k_hw_reg_read(ah, AR5K_TIMER0);
+ atim = ath5k_hw_reg_read(ah, AR5K_TIMER3);
+ dma = ath5k_hw_reg_read(ah, AR5K_TIMER1) >> 3;
+
+ /* NOTE: SWBA is different. Having a wrong window there does not
+ * stop us from sending data and this condition is catched thru
+ * other means (SWBA interrupt) */
+
+ if (ath5k_check_timer_win(nbtt, atim, 1, intval) &&
+ ath5k_check_timer_win(dma, nbtt, AR5K_TUNE_DMA_BEACON_RESP,
+ intval))
+ return true; /* O.K. */
+ return false;
+}
+
+/**
* ath5k_hw_set_coverage_class - Set IEEE 802.11 coverage class
*
* @ah: The &struct ath5k_hw