[1/1] tty/hvc: Use IRQF_SHARED for OPAL hvc consoles

From: Sam Mendoza-Jonas <sam@mendozajonas.com>

BugLink: http://bugs.launchpad.net/bugs/1711401

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>
(upstream cherry-pick of commit bbc3dfe8805de86874b1a1b1429a002e8670043e)
Signed-off-by: Colin Ian King <colin.king@canonical.com>
---
 drivers/tty/hvc/hvc_console.h | 1 +
 drivers/tty/hvc/hvc_irq.c     | 9 +++++++--
 drivers/tty/hvc/hvc_opal.c    | 3 +++
 3 files changed, 11 insertions(+), 2 deletions(-)

On 18.08.2017 14:22, Colin King wrote:
> From: Sam Mendoza-Jonas <sam@mendozajonas.com>
> 
> BugLink: http://bugs.launchpad.net/bugs/1711401
> 
> 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>
> (upstream cherry-pick of commit bbc3dfe8805de86874b1a1b1429a002e8670043e)
> Signed-off-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>

> ---
>  drivers/tty/hvc/hvc_console.h | 1 +
>  drivers/tty/hvc/hvc_irq.c     | 9 +++++++--
>  drivers/tty/hvc/hvc_opal.c    | 3 +++
>  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;
>

Applied to xenial/master-next branch. Thanks.