Re: [PATCH 4/4] ath5k: Use SWI to trigger calibration

[Nick Kossifidis <mick@madwifi-project.org>]

 * Get rid of calibration timer, instead use a software interrupt
   to schedule the calibration tasklet.
    
 a) We don't need a timer for this, there is no need for accuracy
    even with round_jiffies i think this is a waste of resources.
    Also we don't need to run calibration if we are idle (no
    interrupts).
    
 b) When we add ANI support we 'll just extend the poll function
    and calibration tasklet and handle all periodic phy calibration
    on one place (much cleaner).
    
 c) Having calibration on a tasklet is better since during calibration
    we can't transmit or receive (antennas are detached to measure
    noise floor), previously calibration could run in parallel with
    tx/rx and interfere (packet loss).
    
 v2: kill tasklet on stop_hw, stop/wake queues

 Signed-off-by: Nick Kossifidis <mickflemm@gmail.com>

---
 drivers/net/wireless/ath/ath5k/ath5k.h |   16 ++++++++++++++
 drivers/net/wireless/ath/ath5k/base.c  |   36 +++++++++++++++++++++++--------
 drivers/net/wireless/ath/ath5k/base.h  |    3 +-
 drivers/net/wireless/ath/ath5k/phy.c   |   20 +++++++++++++++++
 4 files changed, 64 insertions(+), 11 deletions(-)

diff --git a/drivers/net/wireless/ath/ath5k/ath5k.h b/drivers/net/wireless/ath/ath5k/ath5k.h
index 1047a6c..76cf5b2 100644
--- a/drivers/net/wireless/ath/ath5k/ath5k.h
+++ b/drivers/net/wireless/ath/ath5k/ath5k.h
@@ -919,6 +919,12 @@ enum ath5k_int {
 	AR5K_INT_NOCARD	= 0xffffffff
 };
 
+/* Software interrupts used for calibration */
+enum ath5k_software_interrupt {
+	AR5K_SWI_FULL_CALIBRATION = 0x01,
+	AR5K_SWI_SHORT_CALIBRATION = 0x02,
+};
+
 /*
  * Power management
  */
@@ -1123,6 +1129,15 @@ struct ath5k_hw {
 	/* noise floor from last periodic calibration */
 	s32			ah_noise_floor;
 
+	/* Calibration timestamp */
+	u32			ah_cal_tstamp;
+
+	/* Calibration interval (secs) */
+	u8			ah_cal_intval;
+
+	/* Software interrupt mask */
+	u8			ah_swi_mask;
+
 	/*
 	 * Function pointers
 	 */
@@ -1276,6 +1291,7 @@ extern int ath5k_hw_channel(struct ath5k_hw *ah, struct ieee80211_channel *chann
 /* PHY calibration */
 extern int ath5k_hw_phy_calibrate(struct ath5k_hw *ah, struct ieee80211_channel *channel);
 extern int ath5k_hw_noise_floor_calibration(struct ath5k_hw *ah, short freq);
+extern void ath5k_hw_calibration_poll(struct ath5k_hw *ah);
 /* Spur mitigation */
 bool ath5k_hw_chan_has_spur_noise(struct ath5k_hw *ah,
 				struct ieee80211_channel *channel);
diff --git a/drivers/net/wireless/ath/ath5k/base.c b/drivers/net/wireless/ath/ath5k/base.c
index b64731b..d84ccad 100644
--- a/drivers/net/wireless/ath/ath5k/base.c
+++ b/drivers/net/wireless/ath/ath5k/base.c
@@ -59,7 +59,7 @@
 #include "reg.h"
 #include "debug.h"
 
-static int ath5k_calinterval = 10; /* Calibrate PHY every 10 secs (TODO: Fixme) */
+static u8 ath5k_calinterval = 10; /* Calibrate PHY every 10 secs (TODO: Fixme) */
 static int modparam_nohwcrypt;
 module_param_named(nohwcrypt, modparam_nohwcrypt, bool, S_IRUGO);
 MODULE_PARM_DESC(nohwcrypt, "Disable hardware encryption.");
@@ -376,7 +376,7 @@ static int 	ath5k_stop_hw(struct ath5k_softc *sc);
 static irqreturn_t ath5k_intr(int irq, void *dev_id);
 static void 	ath5k_tasklet_reset(unsigned long data);
 
-static void 	ath5k_calibrate(unsigned long data);
+static void 	ath5k_tasklet_calibrate(unsigned long data);
 
 /*
  * Module init/exit functions
@@ -799,8 +799,8 @@ ath5k_attach(struct pci_dev *pdev, struct ieee80211_hw *hw)
 	tasklet_init(&sc->rxtq, ath5k_tasklet_rx, (unsigned long)sc);
 	tasklet_init(&sc->txtq, ath5k_tasklet_tx, (unsigned long)sc);
 	tasklet_init(&sc->restq, ath5k_tasklet_reset, (unsigned long)sc);
+	tasklet_init(&sc->calib, ath5k_tasklet_calibrate, (unsigned long)sc);
 	tasklet_init(&sc->beacontq, ath5k_tasklet_beacon, (unsigned long)sc);
-	setup_timer(&sc->calib_tim, ath5k_calibrate, (unsigned long)sc);
 
 	ret = ath5k_eeprom_read_mac(ah, mac);
 	if (ret) {
@@ -2366,7 +2366,7 @@ ath5k_init(struct ath5k_softc *sc)
 	sc->curband = &sc->sbands[sc->curchan->band];
 	sc->imask = AR5K_INT_RXOK | AR5K_INT_RXERR | AR5K_INT_RXEOL |
 		AR5K_INT_RXORN | AR5K_INT_TXDESC | AR5K_INT_TXEOL |
-		AR5K_INT_FATAL | AR5K_INT_GLOBAL;
+		AR5K_INT_FATAL | AR5K_INT_GLOBAL | AR5K_INT_SWI;
 	ret = ath5k_reset(sc, NULL);
 	if (ret)
 		goto done;
@@ -2383,8 +2383,8 @@ ath5k_init(struct ath5k_softc *sc)
 	/* Set ack to be sent at low bit-rates */
 	ath5k_hw_set_ack_bitrate_high(ah, false);
 
-	mod_timer(&sc->calib_tim, round_jiffies(jiffies +
-			msecs_to_jiffies(ath5k_calinterval * 1000)));
+	/* Set PHY calibration inteval */
+	ah->ah_cal_intval = ath5k_calinterval;
 
 	ret = 0;
 done:
@@ -2477,10 +2477,10 @@ ath5k_stop_hw(struct ath5k_softc *sc)
 	mmiowb();
 	mutex_unlock(&sc->lock);
 
-	del_timer_sync(&sc->calib_tim);
 	tasklet_kill(&sc->rxtq);
 	tasklet_kill(&sc->txtq);
 	tasklet_kill(&sc->restq);
+	tasklet_kill(&sc->calib);
 	tasklet_kill(&sc->beacontq);
 
 	ath5k_rfkill_hw_stop(sc->ah);
@@ -2536,6 +2536,9 @@ ath5k_intr(int irq, void *dev_id)
 			if (status & AR5K_INT_BMISS) {
 				/* TODO */
 			}
+			if (status & AR5K_INT_SWI) {
+				tasklet_schedule(&sc->calib);
+			}
 			if (status & AR5K_INT_MIB) {
 				/*
 				 * These stats are also used for ANI i think
@@ -2552,6 +2555,8 @@ ath5k_intr(int irq, void *dev_id)
 	if (unlikely(!counter))
 		ATH5K_WARN(sc, "too many interrupts, giving up for now\n");
 
+	ath5k_hw_calibration_poll(ah);
+
 	return IRQ_HANDLED;
 }
 
@@ -2568,11 +2573,19 @@ ath5k_tasklet_reset(unsigned long data)
  * for temperature/environment changes.
  */
 static void
-ath5k_calibrate(unsigned long data)
+ath5k_tasklet_calibrate(unsigned long data)
 {
 	struct ath5k_softc *sc = (void *)data;
 	struct ath5k_hw *ah = sc->ah;
 
+	/* Only full calibration for now */
+	if (ah->ah_swi_mask != AR5K_SWI_FULL_CALIBRATION)
+		return;
+
+	/* Stop queues so that calibration
+	 * doesn't interfere with tx */
+	ieee80211_stop_queues(sc->hw);
+
 	ATH5K_DBG(sc, ATH5K_DEBUG_CALIBRATE, "channel %u/%x\n",
 		ieee80211_frequency_to_channel(sc->curchan->center_freq),
 		sc->curchan->hw_value);
@@ -2590,8 +2603,11 @@ ath5k_calibrate(unsigned long data)
 			ieee80211_frequency_to_channel(
 				sc->curchan->center_freq));
 
-	mod_timer(&sc->calib_tim, round_jiffies(jiffies +
-			msecs_to_jiffies(ath5k_calinterval * 1000)));
+	ah->ah_swi_mask = 0;
+
+	/* Wake queues */
+	ieee80211_wake_queues(sc->hw);
+
 }
 
 
diff --git a/drivers/net/wireless/ath/ath5k/base.h b/drivers/net/wireless/ath/ath5k/base.h
index 778e422..667bd9d 100644
--- a/drivers/net/wireless/ath/ath5k/base.h
+++ b/drivers/net/wireless/ath/ath5k/base.h
@@ -177,6 +177,8 @@ struct ath5k_softc {
 
 	struct ath5k_rfkill	rf_kill;
 
+	struct tasklet_struct	calib;		/* calibration tasklet */
+
 	spinlock_t		block;		/* protects beacon */
 	struct tasklet_struct	beacontq;	/* beacon intr tasklet */
 	struct ath5k_buf	*bbuf;		/* beacon buffer */
@@ -187,7 +189,6 @@ struct ath5k_softc {
 	unsigned int		nexttbtt;	/* next beacon time in TU */
 	struct ath5k_txq	*cabq;		/* content after beacon */
 
-	struct timer_list	calib_tim;	/* calibration timer */
 	int 			power_level;	/* Requested tx power in dbm */
 	bool			assoc;		/* assocate state */
 	bool			enable_beacon;	/* true if beacons are on */
diff --git a/drivers/net/wireless/ath/ath5k/phy.c b/drivers/net/wireless/ath/ath5k/phy.c
index 6afba98..d30bc3b 100644
--- a/drivers/net/wireless/ath/ath5k/phy.c
+++ b/drivers/net/wireless/ath/ath5k/phy.c
@@ -1104,6 +1104,26 @@ int ath5k_hw_channel(struct ath5k_hw *ah, struct ieee80211_channel *channel)
   PHY calibration
 \*****************/
 
+void
+ath5k_hw_calibration_poll(struct ath5k_hw *ah)
+{
+	u32 current_time = (jiffies / HZ);
+	u32 cal_intval = ah->ah_cal_intval;
+
+	if (!ah->ah_cal_tstamp)
+		ah->ah_cal_tstamp = current_time;
+
+	/* For now we always do full calibration
+	 * Mark software interrupt mask and fire software
+	 * interrupt (bit gets auto-cleared) */
+	if ((current_time - ah->ah_cal_tstamp) >= cal_intval) {
+		ah->ah_cal_tstamp = current_time;
+		ah->ah_swi_mask = AR5K_SWI_FULL_CALIBRATION;
+		AR5K_REG_ENABLE_BITS(ah, AR5K_CR, AR5K_CR_SWI);
+	}
+
+}
+
 /**
  * ath5k_hw_noise_floor_calibration - perform PHY noise floor calibration
  *