tty/hvc: Use IRQF_SHARED for OPAL hvc consoles

Commit 2def86a7200c ("hvc: Convert to using interrupts instead of opal
events") enabled the use of interrupts in the hvc_driver for OPAL
platforms. However on machines with more than one hvc console, any
console after the first will fail to register an interrupt handler in
notifier_add_irq() since all consoles share the same IRQ number but do
not set the IRQF_SHARED flag:

  genirq: Flags mismatch irq 31. 00000000 (hvc_console) vs. 00000000 (hvc_console)
  hvc_open: request_irq failed with rc -16.

This error propagates up to hvc_open() and the console is closed, but
OPAL will still generate interrupts that are not handled, leading to
rcu_sched stall warnings.

Set IRQF_SHARED when calling request_irq(), allowing additional consoles
to start properly. This is only set for consoles handled by
hvc_opal_probe(), leaving other types unaffected.

Signed-off-by: Samuel Mendoza-Jonas <sam@mendozajonas.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

3 files changed, 11 insertions, 2 deletions

diff --git a/drivers/tty/hvc/hvc_console.h b/drivers/tty/hvc/hvc_console.h
index 913101980827..798c48d0d32c 100644
--- a/drivers/tty/hvc/hvc_console.h
+++ b/drivers/tty/hvc/hvc_console.h
@@ -60,6 +60,7 @@ struct hvc_struct {
         struct winsize ws;
         struct work_struct tty_resize;
         struct list_head next;
+        unsigned long flags;
 };
 
 /* implemented by a low level driver */
diff --git a/drivers/tty/hvc/hvc_irq.c b/drivers/tty/hvc/hvc_irq.c
index c9adb0559f61..bc7a96874637 100644
--- a/drivers/tty/hvc/hvc_irq.c
+++ b/drivers/tty/hvc/hvc_irq.c
@@ -14,6 +14,11 @@ static irqreturn_t hvc_handle_interrupt(int irq, void *dev_instance)
         /* if hvc_poll request a repoll, then kick the hvcd thread */
         if (hvc_poll(dev_instance))
                 hvc_kick();
+
+        /*
+         * We're safe to always return IRQ_HANDLED as the hvcd thread will
+         * iterate through each hvc_struct.
+         */
         return IRQ_HANDLED;
 }
 
@@ -28,8 +33,8 @@ int notifier_add_irq(struct hvc_struct *hp, int irq)
                 hp->irq_requested = 0;
                 return 0;
         }
-        rc = request_irq(irq, hvc_handle_interrupt, 0,
-                           "hvc_console", hp);
+        rc = request_irq(irq, hvc_handle_interrupt, hp->flags,
+                        "hvc_console", hp);
         if (!rc)
                 hp->irq_requested = 1;
         return rc;
diff --git a/drivers/tty/hvc/hvc_opal.c b/drivers/tty/hvc/hvc_opal.c
index 47b54c6aefd2..b7cd0ae7d927 100644
--- a/drivers/tty/hvc/hvc_opal.c
+++ b/drivers/tty/hvc/hvc_opal.c
@@ -224,6 +224,9 @@ static int hvc_opal_probe(struct platform_device *dev)
         hp = hvc_alloc(termno, irq, ops, MAX_VIO_PUT_CHARS);
         if (IS_ERR(hp))
                 return PTR_ERR(hp);
+
+        /* hvc consoles on powernv may need to share a single irq */
+        hp->flags = IRQF_SHARED;
         dev_set_drvdata(&dev->dev, hp);
 
         return 0;