Re: [PATCH #upstream-fixes] ahci: always clear all bits in irq_stat

[Jeff Garzik <jeff@garzik.org>]

Tejun Heo wrote:
> Some AHCI controllers (ICH7 was reported) set pending bit in
> HOST_IRQ_STAT for non-existent ports and when it's not cleared falls
> into IRQ storm.  Always clear full irq_stat instead of only the bits
> that are handled.  As nothing changes for recognized ports, the risk
> of breaking things is pretty low.
> 
> Reported and verified by Philipp Thomas in the following suse
> bugzilla.
> 
> https://bugzilla.novell.com/attachment.cgi?id=215692
> 
> Signed-off-by: Tejun Heo <tj@kernel.org>
> Cc: Philipp Thomas <pth@novell.com>
> ---
> This should fix some of ahci IRQ storms we have.  I'm not sure it
> fixes the JMB probing one tho.  I think this one is worth committing
> to #upstream-fixes and should be safe.
> 
> Thanks.
> 
>  drivers/ata/ahci.c |    9 +++------
>  1 file changed, 3 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
> index 966ab40..8378334 100644
> --- a/drivers/ata/ahci.c
> +++ b/drivers/ata/ahci.c
> @@ -1760,7 +1760,7 @@ static irqreturn_t ahci_interrupt(int irq, void *dev_instance)
>  	struct ahci_host_priv *hpriv;
>  	unsigned int i, handled = 0;
>  	void __iomem *mmio;
> -	u32 irq_stat, irq_ack = 0;
> +	u32 irq_stat;
>  
>  	VPRINTK("ENTER\n");
>  
> @@ -1792,14 +1792,11 @@ static irqreturn_t ahci_interrupt(int irq, void *dev_instance)
>  					"interrupt on disabled port %u\n", i);
>  		}
>  
> -		irq_ack |= (1 << i);
> -	}
> -
> -	if (irq_ack) {
> -		writel(irq_ack, mmio + HOST_IRQ_STAT);
>  		handled = 1;
>  	}
>  
> +	writel(irq_stat, mmio + HOST_IRQ_STAT);
> +
>  	spin_unlock(&host->lock);
>  

applied