chelsio: cxgb: Replace the workqueue with threaded interrupt

The external interrupt (F_PL_INTR_EXT) needs to be handled in a process
context and this is accomplished by utilizing a workqueue.

The process context can also be provided by a threaded interrupt instead
of a workqueue. The threaded interrupt can be used later for other
interrupt related processing which require non-atomic context without
using yet another workqueue. free_irq() also ensures that the thread is
done which is currently missing (the worker could continue after the
module has been removed).

Save pending flags in pending_thread_intr. Use the same mechanism
to disable F_PL_INTR_EXT as interrupt source like it is used before the
worker is scheduled. Enable the interrupt again once
t1_elmer0_ext_intr_handler() is done.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/chelsio/cxgb/common.h

@@ -238,7 +238,6 @@ struct adapter {
 	int msg_enable;
 	u32 mmio_len;
 
-	struct work_struct ext_intr_handler_task;
 	struct adapter_params params;
 
 	/* Terminator modules. */
@@ -257,6 +256,7 @@ struct adapter {
 
 	/* guards async operations */
 	spinlock_t async_lock ____cacheline_aligned;
+	u32 pending_thread_intr;
 	u32 slow_intr_mask;
 	int t1powersave;
 };
@@ -334,8 +334,7 @@ void t1_interrupts_enable(adapter_t *adapter);
 void t1_interrupts_disable(adapter_t *adapter);
 void t1_interrupts_clear(adapter_t *adapter);
 int t1_elmer0_ext_intr_handler(adapter_t *adapter);
-void t1_elmer0_ext_intr(adapter_t *adapter);
-int t1_slow_intr_handler(adapter_t *adapter);
+irqreturn_t t1_slow_intr_handler(adapter_t *adapter);
 
 int t1_link_start(struct cphy *phy, struct cmac *mac, struct link_config *lc);
 const struct board_info *t1_get_board_info(unsigned int board_id);

drivers/net/ethernet/chelsio/cxgb/cxgb2.c

@@ -211,7 +211,8 @@ static int cxgb_up(struct adapter *adapter)
 	t1_interrupts_clear(adapter);
 
 	adapter->params.has_msi = !disable_msi && !pci_enable_msi(adapter->pdev);
-	err = request_irq(adapter->pdev->irq, t1_interrupt,
+	err = request_threaded_irq(adapter->pdev->irq, t1_interrupt,
+				   t1_interrupt_thread,
 				   adapter->params.has_msi ? 0 : IRQF_SHARED,
 				   adapter->name, adapter);
 	if (err) {
@@ -916,41 +917,6 @@ static void mac_stats_task(struct work_struct *work)
 	spin_unlock(&adapter->work_lock);
 }
 
-/*
- * Processes elmer0 external interrupts in process context.
- */
-static void ext_intr_task(struct work_struct *work)
-{
-	struct adapter *adapter =
-		container_of(work, struct adapter, ext_intr_handler_task);
-
-	t1_elmer0_ext_intr_handler(adapter);
-
-	/* Now reenable external interrupts */
-	spin_lock_irq(&adapter->async_lock);
-	adapter->slow_intr_mask |= F_PL_INTR_EXT;
-	writel(F_PL_INTR_EXT, adapter->regs + A_PL_CAUSE);
-	writel(adapter->slow_intr_mask | F_PL_INTR_SGE_DATA,
-		   adapter->regs + A_PL_ENABLE);
-	spin_unlock_irq(&adapter->async_lock);
-}
-
-/*
- * Interrupt-context handler for elmer0 external interrupts.
- */
-void t1_elmer0_ext_intr(struct adapter *adapter)
-{
-	/*
-	 * Schedule a task to handle external interrupts as we require
-	 * a process context.  We disable EXT interrupts in the interim
-	 * and let the task reenable them when it's done.
-	 */
-	adapter->slow_intr_mask &= ~F_PL_INTR_EXT;
-	writel(adapter->slow_intr_mask | F_PL_INTR_SGE_DATA,
-		   adapter->regs + A_PL_ENABLE);
-	schedule_work(&adapter->ext_intr_handler_task);
-}
-
 void t1_fatal_err(struct adapter *adapter)
 {
 	if (adapter->flags & FULL_INIT_DONE) {
@@ -1062,8 +1028,6 @@ static int init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
 			spin_lock_init(&adapter->async_lock);
 			spin_lock_init(&adapter->mac_lock);
 
-			INIT_WORK(&adapter->ext_intr_handler_task,
-				  ext_intr_task);
 			INIT_DELAYED_WORK(&adapter->stats_update_task,
 					  mac_stats_task);
 

drivers/net/ethernet/chelsio/cxgb/sge.c

@@ -1619,11 +1619,38 @@ int t1_poll(struct napi_struct *napi, int budget)
 	return work_done;
 }
 
+irqreturn_t t1_interrupt_thread(int irq, void *data)
+{
+	struct adapter *adapter = data;
+	u32 pending_thread_intr;
+
+	spin_lock_irq(&adapter->async_lock);
+	pending_thread_intr = adapter->pending_thread_intr;
+	adapter->pending_thread_intr = 0;
+	spin_unlock_irq(&adapter->async_lock);
+
+	if (!pending_thread_intr)
+		return IRQ_NONE;
+
+	if (pending_thread_intr & F_PL_INTR_EXT)
+		t1_elmer0_ext_intr_handler(adapter);
+
+	spin_lock_irq(&adapter->async_lock);
+	adapter->slow_intr_mask |= F_PL_INTR_EXT;
+
+	writel(F_PL_INTR_EXT, adapter->regs + A_PL_CAUSE);
+	writel(adapter->slow_intr_mask | F_PL_INTR_SGE_DATA,
+	       adapter->regs + A_PL_ENABLE);
+	spin_unlock_irq(&adapter->async_lock);
+
+	return IRQ_HANDLED;
+}
+
 irqreturn_t t1_interrupt(int irq, void *data)
 {
 	struct adapter *adapter = data;
 	struct sge *sge = adapter->sge;
-	int handled;
+	irqreturn_t handled;
 
 	if (likely(responses_pending(adapter))) {
 		writel(F_PL_INTR_SGE_DATA, adapter->regs + A_PL_CAUSE);
@@ -1645,10 +1672,10 @@ irqreturn_t t1_interrupt(int irq, void *data)
 	handled = t1_slow_intr_handler(adapter);
 	spin_unlock(&adapter->async_lock);
 
-	if (!handled)
+	if (handled == IRQ_NONE)
 		sge->stats.unhandled_irqs++;
 
-	return IRQ_RETVAL(handled != 0);
+	return handled;
 }
 
 /*

drivers/net/ethernet/chelsio/cxgb/sge.h

@@ -74,6 +74,7 @@ struct sge *t1_sge_create(struct adapter *, struct sge_params *);
 int t1_sge_configure(struct sge *, struct sge_params *);
 int t1_sge_set_coalesce_params(struct sge *, struct sge_params *);
 void t1_sge_destroy(struct sge *);
+irqreturn_t t1_interrupt_thread(int irq, void *data);
 irqreturn_t t1_interrupt(int irq, void *cookie);
 int t1_poll(struct napi_struct *, int);
 

drivers/net/ethernet/chelsio/cxgb/subr.c

@@ -210,7 +210,7 @@ static int fpga_phy_intr_handler(adapter_t *adapter)
 /*
  * Slow path interrupt handler for FPGAs.
  */
-static int fpga_slow_intr(adapter_t *adapter)
+static irqreturn_t fpga_slow_intr(adapter_t *adapter)
 {
 	u32 cause = readl(adapter->regs + A_PL_CAUSE);
 
@@ -238,7 +238,7 @@ static int fpga_slow_intr(adapter_t *adapter)
 	if (cause)
 		writel(cause, adapter->regs + A_PL_CAUSE);
 
-	return cause != 0;
+	return cause == 0 ? IRQ_NONE : IRQ_HANDLED;
 }
 #endif
 
@@ -842,13 +842,14 @@ void t1_interrupts_clear(adapter_t* adapter)
 /*
  * Slow path interrupt handler for ASICs.
  */
-static int asic_slow_intr(adapter_t *adapter)
+static irqreturn_t asic_slow_intr(adapter_t *adapter)
 {
 	u32 cause = readl(adapter->regs + A_PL_CAUSE);
+	irqreturn_t ret = IRQ_HANDLED;
 
 	cause &= adapter->slow_intr_mask;
 	if (!cause)
-		return 0;
+		return IRQ_NONE;
 	if (cause & F_PL_INTR_SGE_ERR)
 		t1_sge_intr_error_handler(adapter->sge);
 	if (cause & F_PL_INTR_TP)
@@ -857,16 +858,25 @@ static int asic_slow_intr(adapter_t *adapter)
 		t1_espi_intr_handler(adapter->espi);
 	if (cause & F_PL_INTR_PCIX)
 		t1_pci_intr_handler(adapter);
-	if (cause & F_PL_INTR_EXT)
-		t1_elmer0_ext_intr(adapter);
+	if (cause & F_PL_INTR_EXT) {
+		/* Wake the threaded interrupt to handle external interrupts as
+		 * we require a process context. We disable EXT interrupts in
+		 * the interim and let the thread reenable them when it's done.
+		 */
+		adapter->pending_thread_intr |= F_PL_INTR_EXT;
+		adapter->slow_intr_mask &= ~F_PL_INTR_EXT;
+		writel(adapter->slow_intr_mask | F_PL_INTR_SGE_DATA,
+		       adapter->regs + A_PL_ENABLE);
+		ret = IRQ_WAKE_THREAD;
+	}
 
 	/* Clear the interrupts just processed. */
 	writel(cause, adapter->regs + A_PL_CAUSE);
 	readl(adapter->regs + A_PL_CAUSE); /* flush writes */
-	return 1;
+	return ret;
 }
 
-int t1_slow_intr_handler(adapter_t *adapter)
+irqreturn_t t1_slow_intr_handler(adapter_t *adapter)
 {
 #ifdef CONFIG_CHELSIO_T1_1G
 	if (!t1_is_asic(adapter))