rt2x00: Convert rt2800pci to use tasklets

Fix interrupt processing on slow machines by using individual tasklets
for each different device interrupt. This ensures that while a RX or TX
status tasklet is scheduled only the according device interrupt is
masked and other interrupts such as TBTT can still be processed.

Also, this allows us to use tasklet_hi_schedule for TBTT and PRETBTT
processing which is required to not send out beacons with a wrong DTIM
count (due to delayed periodic beacon updates). Furthermore, this
improves the latency between the TBTT and sending out buffered multi-
and broadcast traffic.

As a nice bonus, the interrupt handling overhead is reduced such that
rt2800pci gains around 25% more throuhput on a rt3052 MIPS board.

Signed-off-by: Helmut Schaa <helmut.schaa@googlemail.com>
Acked-by: Gertjan van Wingerde <gwingerde@gmail.com>
Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 114 insertions, 59 deletions

diff --git a/drivers/net/wireless/rt2x00/rt2800pci.c b/drivers/net/wireless/rt2x00/rt2800pci.c
index e4d97ad25bf4..31483c79a457 100644
--- a/drivers/net/wireless/rt2x00/rt2800pci.c
+++ b/drivers/net/wireless/rt2x00/rt2800pci.c
@@ -200,6 +200,13 @@ static void rt2800pci_start_queue(struct data_queue *queue)
                 rt2800_register_write(rt2x00dev, MAC_SYS_CTRL, reg);
                 break;
         case QID_BEACON:
+                /*
+                 * Allow beacon tasklets to be scheduled for periodic
+                 * beacon updates.
+                 */
+                tasklet_enable(&rt2x00dev->tbtt_tasklet);
+                tasklet_enable(&rt2x00dev->pretbtt_tasklet);
+
                 rt2800_register_read(rt2x00dev, BCN_TIME_CFG, &reg);
                 rt2x00_set_field32(&reg, BCN_TIME_CFG_TSF_TICKING, 1);
                 rt2x00_set_field32(&reg, BCN_TIME_CFG_TBTT_ENABLE, 1);
@@ -258,6 +265,12 @@ static void rt2800pci_stop_queue(struct data_queue *queue)
                 rt2800_register_read(rt2x00dev, INT_TIMER_EN, &reg);
                 rt2x00_set_field32(&reg, INT_TIMER_EN_PRE_TBTT_TIMER, 0);
                 rt2800_register_write(rt2x00dev, INT_TIMER_EN, reg);
+
+                /*
+                 * Wait for tbtt tasklets to finish.
+                 */
+                tasklet_disable(&rt2x00dev->tbtt_tasklet);
+                tasklet_disable(&rt2x00dev->pretbtt_tasklet);
                 break;
         default:
                 break;
@@ -408,6 +421,7 @@ static void rt2800pci_toggle_irq(struct rt2x00_dev *rt2x00dev,
         int mask = (state == STATE_RADIO_IRQ_ON) ||
                    (state == STATE_RADIO_IRQ_ON_ISR);
         u32 reg;
+        unsigned long flags;
 
         /*
          * When interrupts are being enabled, the interrupt registers
@@ -417,10 +431,16 @@ static void rt2800pci_toggle_irq(struct rt2x00_dev *rt2x00dev,
                 rt2800_register_read(rt2x00dev, INT_SOURCE_CSR, &reg);
                 rt2800_register_write(rt2x00dev, INT_SOURCE_CSR, reg);
 
+                /*
+                 * Enable tasklets. The beacon related tasklets are
+                 * enabled when the beacon queue is started.
+                 */
                 tasklet_enable(&rt2x00dev->txstatus_tasklet);
-        } else if (state == STATE_RADIO_IRQ_OFF)
-                tasklet_disable(&rt2x00dev->txstatus_tasklet);
+                tasklet_enable(&rt2x00dev->rxdone_tasklet);
+                tasklet_enable(&rt2x00dev->autowake_tasklet);
+        }
 
+        spin_lock_irqsave(&rt2x00dev->irqmask_lock, flags);
         rt2800_register_read(rt2x00dev, INT_MASK_CSR, &reg);
         rt2x00_set_field32(&reg, INT_MASK_CSR_RXDELAYINT, 0);
         rt2x00_set_field32(&reg, INT_MASK_CSR_TXDELAYINT, 0);
@@ -441,6 +461,17 @@ static void rt2800pci_toggle_irq(struct rt2x00_dev *rt2x00dev,
         rt2x00_set_field32(&reg, INT_MASK_CSR_RX_COHERENT, 0);
         rt2x00_set_field32(&reg, INT_MASK_CSR_TX_COHERENT, 0);
         rt2800_register_write(rt2x00dev, INT_MASK_CSR, reg);
+        spin_unlock_irqrestore(&rt2x00dev->irqmask_lock, flags);
+
+        if (state == STATE_RADIO_IRQ_OFF) {
+                /*
+                 * Ensure that all tasklets are finished before
+                 * disabling the interrupts.
+                 */
+                tasklet_disable(&rt2x00dev->txstatus_tasklet);
+                tasklet_disable(&rt2x00dev->rxdone_tasklet);
+                tasklet_disable(&rt2x00dev->autowake_tasklet);
+        }
 }
 
 static int rt2800pci_init_registers(struct rt2x00_dev *rt2x00dev)
@@ -721,45 +752,60 @@ static void rt2800pci_txdone(struct rt2x00_dev *rt2x00dev)
         }
 }
 
-static void rt2800pci_txstatus_tasklet(unsigned long data)
-{
-        rt2800pci_txdone((struct rt2x00_dev *)data);
-}
-
-static irqreturn_t rt2800pci_interrupt_thread(int irq, void *dev_instance)
+static void rt2800pci_enable_interrupt(struct rt2x00_dev *rt2x00dev,
+                                       struct rt2x00_field32 irq_field)
 {
-        struct rt2x00_dev *rt2x00dev = dev_instance;
-        u32 reg = rt2x00dev->irqvalue[0];
+        unsigned long flags;
+        u32 reg;
 
         /*
-         * 1 - Pre TBTT interrupt.
+         * Enable a single interrupt. The interrupt mask register
+         * access needs locking.
          */
-        if (rt2x00_get_field32(reg, INT_SOURCE_CSR_PRE_TBTT))
-                rt2x00lib_pretbtt(rt2x00dev);
+        spin_lock_irqsave(&rt2x00dev->irqmask_lock, flags);
+        rt2800_register_read(rt2x00dev, INT_MASK_CSR, &reg);
+        rt2x00_set_field32(&reg, irq_field, 1);
+        rt2800_register_write(rt2x00dev, INT_MASK_CSR, reg);
+        spin_unlock_irqrestore(&rt2x00dev->irqmask_lock, flags);
+}
 
-        /*
-         * 2 - Beacondone interrupt.
-         */
-        if (rt2x00_get_field32(reg, INT_SOURCE_CSR_TBTT))
-                rt2x00lib_beacondone(rt2x00dev);
+static void rt2800pci_txstatus_tasklet(unsigned long data)
+{
+        rt2800pci_txdone((struct rt2x00_dev *)data);
 
         /*
-         * 3 - Rx ring done interrupt.
+         * No need to enable the tx status interrupt here as we always
+         * leave it enabled to minimize the possibility of a tx status
+         * register overflow. See comment in interrupt handler.
          */
-        if (rt2x00_get_field32(reg, INT_SOURCE_CSR_RX_DONE))
-                rt2x00pci_rxdone(rt2x00dev);
+}
 
-        /*
-         * 4 - Auto wakeup interrupt.
-         */
-        if (rt2x00_get_field32(reg, INT_SOURCE_CSR_AUTO_WAKEUP))
-                rt2800pci_wakeup(rt2x00dev);
+static void rt2800pci_pretbtt_tasklet(unsigned long data)
+{
+        struct rt2x00_dev *rt2x00dev = (struct rt2x00_dev *)data;
+        rt2x00lib_pretbtt(rt2x00dev);
+        rt2800pci_enable_interrupt(rt2x00dev, INT_MASK_CSR_PRE_TBTT);
+}
 
-        /* Enable interrupts again. */
-        rt2x00dev->ops->lib->set_device_state(rt2x00dev,
-                                              STATE_RADIO_IRQ_ON_ISR);
+static void rt2800pci_tbtt_tasklet(unsigned long data)
+{
+        struct rt2x00_dev *rt2x00dev = (struct rt2x00_dev *)data;
+        rt2x00lib_beacondone(rt2x00dev);
+        rt2800pci_enable_interrupt(rt2x00dev, INT_MASK_CSR_TBTT);
+}
 
-        return IRQ_HANDLED;
+static void rt2800pci_rxdone_tasklet(unsigned long data)
+{
+        struct rt2x00_dev *rt2x00dev = (struct rt2x00_dev *)data;
+        rt2x00pci_rxdone(rt2x00dev);
+        rt2800pci_enable_interrupt(rt2x00dev, INT_MASK_CSR_RX_DONE);
+}
+
+static void rt2800pci_autowake_tasklet(unsigned long data)
+{
+        struct rt2x00_dev *rt2x00dev = (struct rt2x00_dev *)data;
+        rt2800pci_wakeup(rt2x00dev);
+        rt2800pci_enable_interrupt(rt2x00dev, INT_MASK_CSR_AUTO_WAKEUP);
 }
 
 static void rt2800pci_txstatus_interrupt(struct rt2x00_dev *rt2x00dev)
@@ -805,8 +851,8 @@ static void rt2800pci_txstatus_interrupt(struct rt2x00_dev *rt2x00dev)
 static irqreturn_t rt2800pci_interrupt(int irq, void *dev_instance)
 {
         struct rt2x00_dev *rt2x00dev = dev_instance;
-        u32 reg;
-        irqreturn_t ret = IRQ_HANDLED;
+        u32 reg, mask;
+        unsigned long flags;
 
         /* Read status and ACK all interrupts */
         rt2800_register_read(rt2x00dev, INT_SOURCE_CSR, &reg);
@@ -818,38 +864,44 @@ static irqreturn_t rt2800pci_interrupt(int irq, void *dev_instance)
         if (!test_bit(DEVICE_STATE_ENABLED_RADIO, &rt2x00dev->flags))
                 return IRQ_HANDLED;
 
-        if (rt2x00_get_field32(reg, INT_SOURCE_CSR_TX_FIFO_STATUS))
-                rt2800pci_txstatus_interrupt(rt2x00dev);
+        /*
+         * Since INT_MASK_CSR and INT_SOURCE_CSR use the same bits
+         * for interrupts and interrupt masks we can just use the value of
+         * INT_SOURCE_CSR to create the interrupt mask.
+         */
+        mask = ~reg;
 
-        if (rt2x00_get_field32(reg, INT_SOURCE_CSR_PRE_TBTT) ||
-            rt2x00_get_field32(reg, INT_SOURCE_CSR_TBTT) ||
-            rt2x00_get_field32(reg, INT_SOURCE_CSR_RX_DONE) ||
-            rt2x00_get_field32(reg, INT_SOURCE_CSR_AUTO_WAKEUP)) {
+        if (rt2x00_get_field32(reg, INT_SOURCE_CSR_TX_FIFO_STATUS)) {
+                rt2800pci_txstatus_interrupt(rt2x00dev);
                 /*
-                 * All other interrupts are handled in the interrupt thread.
-                 * Store irqvalue for use in the interrupt thread.
+                 * Never disable the TX_FIFO_STATUS interrupt.
                  */
-                rt2x00dev->irqvalue[0] = reg;
+                rt2x00_set_field32(&mask, INT_MASK_CSR_TX_FIFO_STATUS, 1);
+        }
 
-                /*
-                 * Disable interrupts, will be enabled again in the
-                 * interrupt thread.
-                */
-                rt2x00dev->ops->lib->set_device_state(rt2x00dev,
-                                                      STATE_RADIO_IRQ_OFF_ISR);
+        if (rt2x00_get_field32(reg, INT_SOURCE_CSR_PRE_TBTT))
+                tasklet_hi_schedule(&rt2x00dev->pretbtt_tasklet);
 
-                /*
-                 * Leave the TX_FIFO_STATUS interrupt enabled to not lose any
-                 * tx status reports.
-                 */
-                rt2800_register_read(rt2x00dev, INT_MASK_CSR, &reg);
-                rt2x00_set_field32(&reg, INT_MASK_CSR_TX_FIFO_STATUS, 1);
-                rt2800_register_write(rt2x00dev, INT_MASK_CSR, reg);
+        if (rt2x00_get_field32(reg, INT_SOURCE_CSR_TBTT))
+                tasklet_hi_schedule(&rt2x00dev->tbtt_tasklet);
 
-                ret = IRQ_WAKE_THREAD;
-        }
+        if (rt2x00_get_field32(reg, INT_SOURCE_CSR_RX_DONE))
+                tasklet_schedule(&rt2x00dev->rxdone_tasklet);
 
-        return ret;
+        if (rt2x00_get_field32(reg, INT_SOURCE_CSR_AUTO_WAKEUP))
+                tasklet_schedule(&rt2x00dev->autowake_tasklet);
+
+        /*
+         * Disable all interrupts for which a tasklet was scheduled right now,
+         * the tasklet will reenable the appropriate interrupts.
+         */
+        spin_lock_irqsave(&rt2x00dev->irqmask_lock, flags);
+        rt2800_register_read(rt2x00dev, INT_MASK_CSR, &reg);
+        reg &= mask;
+        rt2800_register_write(rt2x00dev, INT_MASK_CSR, reg);
+        spin_unlock_irqrestore(&rt2x00dev->irqmask_lock, flags);
+
+        return IRQ_HANDLED;
 }
 
 /*
@@ -964,8 +1016,11 @@ static const struct rt2800_ops rt2800pci_rt2800_ops = {
 
 static const struct rt2x00lib_ops rt2800pci_rt2x00_ops = {
         .irq_handler            = rt2800pci_interrupt,
-        .irq_handler_thread     = rt2800pci_interrupt_thread,
-        .txstatus_tasklet       = rt2800pci_txstatus_tasklet,
+        .txstatus_tasklet       = rt2800pci_txstatus_tasklet,
+        .pretbtt_tasklet        = rt2800pci_pretbtt_tasklet,
+        .tbtt_tasklet           = rt2800pci_tbtt_tasklet,
+        .rxdone_tasklet         = rt2800pci_rxdone_tasklet,
+        .autowake_tasklet       = rt2800pci_autowake_tasklet,
         .probe_hw               = rt2800pci_probe_hw,
         .get_firmware_name      = rt2800pci_get_firmware_name,
         .check_firmware         = rt2800_check_firmware,