[RFC PATCH 2/3] chelsio: cxgb: Move slow interrupt handling to threaded irqs

[Ahmed S. Darwish]

The t1_interrupt() irq handler calls del_timer_sync() down the chain:

   sge.c: t1_interrupt()
     -> subr.c: t1_slow_intr_handler()
       -> asic_slow_intr() || fpga_slow_intr()
         -> t1_pci_intr_handler()
           -> cxgb2.c: t1_fatal_err()           # Cont. at [*]
       -> fpga_slow_intr()
         -> sge.c: t1_sge_intr_error_handler()
           -> cxgb2.c: t1_fatal_err()           # Cont. at [*]

[*] cxgb2.c: t1_fatal_err()
      -> sge.c: t1_sge_stop()
        -> timer.c: del_timer_sync()

This is invalid: if an irq handler calls del_timer_sync() on a timer it
has already interrupted, it will loop forever.

Move the slow t1 interrupt handling path, t1_slow_intr_handler(), to a
threaded-irq task context.

Signed-off-by: Ahmed S. Darwish <a.darw...@linutronix.de>
---
 drivers/net/ethernet/chelsio/cxgb/cxgb2.c |  6 +++---
 drivers/net/ethernet/chelsio/cxgb/sge.c   | 13 +++++++++++--
 drivers/net/ethernet/chelsio/cxgb/sge.h   |  3 ++-
 3 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/chelsio/cxgb/cxgb2.c 
b/drivers/net/ethernet/chelsio/cxgb/cxgb2.c
index 7b5a98330ef7..c96bdca4f270 100644
--- a/drivers/net/ethernet/chelsio/cxgb/cxgb2.c
+++ b/drivers/net/ethernet/chelsio/cxgb/cxgb2.c
@@ -211,9 +211,9 @@ 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,
-                         adapter->params.has_msi ? 0 : IRQF_SHARED,
-                         adapter->name, adapter);
+       err = request_threaded_irq(adapter->pdev->irq, t1_irq, t1_irq_thread,
+                                  adapter->params.has_msi ? 0 : IRQF_SHARED,
+                                  adapter->name, adapter);
        if (err) {
                if (adapter->params.has_msi)
                        pci_disable_msi(adapter->pdev);
diff --git a/drivers/net/ethernet/chelsio/cxgb/sge.c 
b/drivers/net/ethernet/chelsio/cxgb/sge.c
index d6df1a87db0b..f1c402f6b889 100644
--- a/drivers/net/ethernet/chelsio/cxgb/sge.c
+++ b/drivers/net/ethernet/chelsio/cxgb/sge.c
@@ -1626,11 +1626,10 @@ int t1_poll(struct napi_struct *napi, int budget)
        return work_done;
 }
 
-irqreturn_t t1_interrupt(int irq, void *data)
+irqreturn_t t1_irq(int irq, void *data)
 {
        struct adapter *adapter = data;
        struct sge *sge = adapter->sge;
-       int handled;
 
        if (likely(responses_pending(adapter))) {
                writel(F_PL_INTR_SGE_DATA, adapter->regs + A_PL_CAUSE);
@@ -1645,9 +1644,19 @@ irqreturn_t t1_interrupt(int irq, void *data)
                                napi_enable(&adapter->napi);
                        }
                }
+
                return IRQ_HANDLED;
        }
 
+       return IRQ_WAKE_THREAD;
+}
+
+irqreturn_t t1_irq_thread(int irq, void *data)
+{
+       struct adapter *adapter = data;
+       struct sge *sge = adapter->sge;
+       int handled;
+
        spin_lock(&adapter->async_lock);
        handled = t1_slow_intr_handler(adapter);
        spin_unlock(&adapter->async_lock);
diff --git a/drivers/net/ethernet/chelsio/cxgb/sge.h 
b/drivers/net/ethernet/chelsio/cxgb/sge.h
index a1ba591b3431..4072b3fb312b 100644
--- a/drivers/net/ethernet/chelsio/cxgb/sge.h
+++ b/drivers/net/ethernet/chelsio/cxgb/sge.h
@@ -74,7 +74,8 @@ 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(int irq, void *cookie);
+irqreturn_t t1_irq(int irq, void *cookie);
+irqreturn_t t1_irq_thread(int irq, void *cookie);
 int t1_poll(struct napi_struct *, int);
 
 netdev_tx_t t1_start_xmit(struct sk_buff *skb, struct net_device *dev);
-- 
2.29.2