Subject: [PATCH 2/2] bcm43xx: preemptible periodic work

From: Michael Buesch <[email-masked]>
Date: Mon, 5 Jun 2006 20:24:21 +0200

John, please queue for 2.6.18.
This patch depends on
[PATCH 1/2] bcm43xx: redesign locking

--

Make the heavy periodic work preemptible to avoid disabling
local IRQs for several msecs.

Signed-off-by: Michael Buesch <[email-masked]>

Index: wireless-dev/drivers/net/wireless/bcm43xx/bcm43xx_main.c
===================================================================
--- wireless-dev.orig/drivers/net/wireless/bcm43xx/bcm43xx_main.c	2006-06-05 20:17:31.000000000 +0200
+++ wireless-dev/drivers/net/wireless/bcm43xx/bcm43xx_main.c	2006-06-05 20:17:36.000000000 +0200
@@ -496,11 +496,21 @@
 	return old_mask;
 }
 
+/* Synchronize IRQ top- and bottom-half.
+ * IRQs must be masked before calling this.
+ * This must not be called with the irq_lock held.
+ */
+static void bcm43xx_synchronize_irq(struct bcm43xx_private *bcm)
+{
+	synchronize_irq(bcm->irq);
+	tasklet_disable(&bcm->isr_tasklet);
+}
+
 /* Make sure we don't receive more data from the device. */
 static int bcm43xx_disable_interrupts_sync(struct bcm43xx_private *bcm, u32 *oldstate)
 {
-	u32 old;
 	unsigned long flags;
+	u32 old;
 
 	bcm43xx_lock_irqonly(bcm, flags);
 	if (unlikely(bcm43xx_status(bcm) != BCM43xx_STAT_INITIALIZED)) {
@@ -508,8 +518,9 @@
 		return -EBUSY;
 	}
 	old = bcm43xx_interrupt_disable(bcm, BCM43xx_IRQ_ALL);
-	tasklet_disable(&bcm->isr_tasklet);
 	bcm43xx_unlock_irqonly(bcm, flags);
+	bcm43xx_synchronize_irq(bcm);
+
 	if (oldstate)
 		*oldstate = old;
 
@@ -3106,14 +3117,10 @@
 	//TODO for APHY (temperature?)
 }
 
-static void bcm43xx_periodic_work_handler(void *d)
+static void do_periodic_work(struct bcm43xx_private *bcm)
 {
-	struct bcm43xx_private *bcm = d;
-	unsigned long flags;
 	unsigned int state;
 
-	bcm43xx_lock_irqsafe(bcm, flags);
-
 	state = bcm->periodic_state;
 	if (state % 8 == 0)
 		bcm43xx_periodic_every120sec(bcm);
@@ -3121,13 +3128,79 @@
 		bcm43xx_periodic_every60sec(bcm);
 	if (state % 2 == 0)
 		bcm43xx_periodic_every30sec(bcm);
-	bcm43xx_periodic_every15sec(bcm);
+	if (state % 1 == 0)
+		bcm43xx_periodic_every15sec(bcm);
 	bcm->periodic_state = state + 1;
 
 	schedule_delayed_work(&bcm->periodic_work, HZ * 15);
+}
 
-	mmiowb();
-	bcm43xx_unlock_irqsafe(bcm, flags);
+/* Estimate a "Badness" value based on the periodic work
+ * state-machine state. "Badness" is worse (bigger), if the
+ * periodic work will take longer.
+ */
+static int estimate_periodic_work_badness(unsigned int state)
+{
+	int badness = 0;
+
+	if (state % 8 == 0) /* every 120 sec */
+		badness += 10;
+	if (state % 4 == 0) /* every 60 sec */
+		badness += 5;
+	if (state % 2 == 0) /* every 30 sec */
+		badness += 1;
+	if (state % 1 == 0) /* every 15 sec */
+		badness += 1;
+
+#define BADNESS_LIMIT	4
+	return badness;
+}
+
+static void bcm43xx_periodic_work_handler(void *d)
+{
+	struct bcm43xx_private *bcm = d;
+	unsigned long flags;
+	u32 savedirqs = 0;
+	int badness;
+
+	badness = estimate_periodic_work_badness(bcm->periodic_state);
+	if (badness > BADNESS_LIMIT) {
+		/* Periodic work will take a long time, so we want it to
+		 * be preemtible.
+		 */
+		bcm43xx_lock_irqonly(bcm, flags);
+		netif_stop_queue(bcm->net_dev);
+		if (bcm43xx_using_pio(bcm))
+			bcm43xx_pio_freeze_txqueues(bcm);
+		savedirqs = bcm43xx_interrupt_disable(bcm, BCM43xx_IRQ_ALL);
+		bcm43xx_unlock_irqonly(bcm, flags);
+		bcm43xx_lock_noirq(bcm);
+		bcm43xx_synchronize_irq(bcm);
+	} else {
+		/* Periodic work should take short time, so we want low
+		 * locking overhead.
+		 */
+		bcm43xx_lock_irqsafe(bcm, flags);
+	}
+
+	do_periodic_work(bcm);
+
+	if (badness > BADNESS_LIMIT) {
+		bcm43xx_lock_irqonly(bcm, flags);
+		if (likely(bcm43xx_status(bcm) == BCM43xx_STAT_INITIALIZED)) {
+			tasklet_enable(&bcm->isr_tasklet);
+			bcm43xx_interrupt_enable(bcm, savedirqs);
+			if (bcm43xx_using_pio(bcm))
+				bcm43xx_pio_thaw_txqueues(bcm);
+		}
+		netif_wake_queue(bcm->net_dev);
+		mmiowb();
+		bcm43xx_unlock_irqonly(bcm, flags);
+		bcm43xx_unlock_noirq(bcm);
+	} else {
+		mmiowb();
+		bcm43xx_unlock_irqsafe(bcm, flags);
+	}
 }
 
 static void bcm43xx_periodic_tasks_delete(struct bcm43xx_private *bcm)
@@ -3679,9 +3752,11 @@
 static int bcm43xx_net_stop(struct net_device *net_dev)
 {
 	struct bcm43xx_private *bcm = bcm43xx_priv(net_dev);
+	int err;
 
 	ieee80211softmac_stop(net_dev);
-	bcm43xx_disable_interrupts_sync(bcm, NULL);
+	err = bcm43xx_disable_interrupts_sync(bcm, NULL);
+	assert(!err);
 	bcm43xx_free_board(bcm);
 
 	return 0;
Index: wireless-dev/drivers/net/wireless/bcm43xx/bcm43xx_phy.c
===================================================================
--- wireless-dev.orig/drivers/net/wireless/bcm43xx/bcm43xx_phy.c	2006-06-05 20:17:31.000000000 +0200
+++ wireless-dev/drivers/net/wireless/bcm43xx/bcm43xx_phy.c	2006-06-05 20:17:36.000000000 +0200
@@ -1410,7 +1410,10 @@
 u16 bcm43xx_phy_lo_g_deviation_subval(struct bcm43xx_private *bcm, u16 control)
 {
 	struct bcm43xx_phyinfo *phy = bcm43xx_current_phy(bcm);
+	u16 ret;
+	unsigned long flags;
 
+	local_irq_save(flags);
 	if (phy->connected) {
 		bcm43xx_phy_write(bcm, 0x15, 0xE300);
 		control <<= 8;
@@ -1430,8 +1433,10 @@
 		bcm43xx_phy_write(bcm, 0x0015, control | 0xFFE0);
 		udelay(8);
 	}
+	ret = bcm43xx_phy_read(bcm, 0x002D);
+	local_irq_restore(flags);
 
-	return bcm43xx_phy_read(bcm, 0x002D);
+	return ret;
 }
 
 static u32 bcm43xx_phy_lo_g_singledeviation(struct bcm43xx_private *bcm, u16 control)
Index: wireless-dev/drivers/net/wireless/bcm43xx/bcm43xx_pio.c
===================================================================
--- wireless-dev.orig/drivers/net/wireless/bcm43xx/bcm43xx_pio.c	2006-06-05 20:17:31.000000000 +0200
+++ wireless-dev/drivers/net/wireless/bcm43xx/bcm43xx_pio.c	2006-06-05 20:17:36.000000000 +0200
@@ -264,6 +264,8 @@
 
 	bcm43xx_lock_irqonly(bcm, flags);
 
+	if (queue->tx_frozen)
+		goto out_unlock;
 	txctl = bcm43xx_pio_read(queue, BCM43xx_PIO_TXCTL);
 	if (txctl & BCM43xx_PIO_TXCTL_SUSPEND)
 		goto out_unlock;
@@ -633,5 +635,40 @@
 			  bcm43xx_pio_read(queue, BCM43xx_PIO_TXCTL)
 			  & ~BCM43xx_PIO_TXCTL_SUSPEND);
 	bcm43xx_power_saving_ctl_bits(queue->bcm, -1, -1);
-	tasklet_schedule(&queue->txtask);
+	if (!list_empty(&queue->txqueue))
+		tasklet_schedule(&queue->txtask);
+}
+
+void bcm43xx_pio_freeze_txqueues(struct bcm43xx_private *bcm)
+{
+	struct bcm43xx_pio *pio;
+
+	assert(bcm43xx_using_pio(bcm));
+	pio = bcm43xx_current_pio(bcm);
+	pio->queue0->tx_frozen = 1;
+	pio->queue1->tx_frozen = 1;
+	pio->queue2->tx_frozen = 1;
+	pio->queue3->tx_frozen = 1;
 }
+
+void bcm43xx_pio_thaw_txqueues(struct bcm43xx_private *bcm)
+{
+	struct bcm43xx_pio *pio;
+
+	assert(bcm43xx_using_pio(bcm));
+	pio = bcm43xx_current_pio(bcm);
+	pio->queue0->tx_frozen = 0;
+	pio->queue1->tx_frozen = 0;
+	pio->queue2->tx_frozen = 0;
+	pio->queue3->tx_frozen = 0;
+	if (!list_empty(&pio->queue0->txqueue))
+		tasklet_schedule(&pio->queue0->txtask);
+	if (!list_empty(&pio->queue1->txqueue))
+		tasklet_schedule(&pio->queue1->txtask);
+	if (!list_empty(&pio->queue2->txqueue))
+		tasklet_schedule(&pio->queue2->txtask);
+	if (!list_empty(&pio->queue3->txqueue))
+		tasklet_schedule(&pio->queue3->txtask);
+}
+
+
Index: wireless-dev/drivers/net/wireless/bcm43xx/bcm43xx_pio.h
===================================================================
--- wireless-dev.orig/drivers/net/wireless/bcm43xx/bcm43xx_pio.h	2006-06-05 20:17:31.000000000 +0200
+++ wireless-dev/drivers/net/wireless/bcm43xx/bcm43xx_pio.h	2006-06-05 20:17:36.000000000 +0200
@@ -54,6 +54,7 @@
 	u16 mmio_base;
 
 	u8 tx_suspended:1,
+	   tx_frozen:1,
 	   need_workarounds:1; /* Workarounds needed for core.rev < 3 */
 
 	/* Adjusted size of the device internal TX buffer. */
@@ -108,8 +109,12 @@
 				   struct bcm43xx_xmitstatus *status);
 void bcm43xx_pio_rx(struct bcm43xx_pioqueue *queue);
 
+/* Suspend a TX queue on hardware level. */
 void bcm43xx_pio_tx_suspend(struct bcm43xx_pioqueue *queue);
 void bcm43xx_pio_tx_resume(struct bcm43xx_pioqueue *queue);
+/* Suspend (freeze) the TX tasklet (software level). */
+void bcm43xx_pio_freeze_txqueues(struct bcm43xx_private *bcm);
+void bcm43xx_pio_thaw_txqueues(struct bcm43xx_private *bcm);
 
 #else /* CONFIG_BCM43XX_PIO */
 
@@ -145,6 +150,14 @@
 void bcm43xx_pio_tx_resume(struct bcm43xx_pioqueue *queue)
 {
 }
+static inline
+void bcm43xx_pio_freeze_txqueues(struct bcm43xx_private *bcm)
+{
+}
+static inline
+void bcm43xx_pio_thaw_txqueues(struct bcm43xx_private *bcm)
+{
+}
 
 #endif /* CONFIG_BCM43XX_PIO */
 #endif /* BCM43xx_PIO_H_ */

-- 
Greetings Michael.