[PATCH 2.6.25] igb: fix legacy mode irq issue

[PATCH 2.6.25] igb: fix legacy mode irq issue

[Andy Gospodarek]

I booted an igb kernel with the option pci=nomsi and instantly noticed
that interrupts no longer worked on my igb device.  I took a look at the
interrupt initialization and quickly discovered a comment stating:

"DO NOT USE EIAME or IAME in legacy mode"

It seemed a bit odd that bits to enable IAM were being set in legacy
interrupt mode, so I dropped out the following parts and interrupts
began working fine again.

Signed-off-by: Andy Gospodarek <andy@greyhouse.net>
---

 igb_main.c |    3 ---
 1 files changed, 3 deletions(-)

diff --git a/drivers/net/igb/igb_main.c b/drivers/net/igb/igb_main.c
index f3c144d..be5da09 100644
--- a/drivers/net/igb/igb_main.c
+++ b/drivers/net/igb/igb_main.c
@@ -472,9 +471,6 @@ static int igb_request_irq(struct igb_adapter *adapter)
 		goto request_done;
 	}
 
-	/* enable IAM, auto-mask */
-	wr32(E1000_IAM, IMS_ENABLE_MASK);
-
 request_done:
 	return err;
 }

Re: [PATCH 2.6.25] igb: fix legacy mode irq issue

[Kok, Auke]

Andy Gospodarek wrote:
> I booted an igb kernel with the option pci=nomsi and instantly noticed
> that interrupts no longer worked on my igb device.  I took a look at the
> interrupt initialization and quickly discovered a comment stating:
> 
> "DO NOT USE EIAME or IAME in legacy mode"
> 
> It seemed a bit odd that bits to enable IAM were being set in legacy
> interrupt mode, so I dropped out the following parts and interrupts
> began working fine again.
> 
> Signed-off-by: Andy Gospodarek <andy@greyhouse.net>

looks valid, I'll test and see, thanks Andy

Auke


> ---
> 
>  igb_main.c |    3 ---
>  1 files changed, 3 deletions(-)
> 
> diff --git a/drivers/net/igb/igb_main.c b/drivers/net/igb/igb_main.c
> index f3c144d..be5da09 100644
> --- a/drivers/net/igb/igb_main.c
> +++ b/drivers/net/igb/igb_main.c
> @@ -472,9 +471,6 @@ static int igb_request_irq(struct igb_adapter *adapter)
>  		goto request_done;
>  	}
>  
> -	/* enable IAM, auto-mask */
> -	wr32(E1000_IAM, IMS_ENABLE_MASK);
> -
>  request_done:
>  	return err;
>  }
> --
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Re: [PATCH 2.6.25] igb: fix legacy mode irq issue

[Jeff Garzik]

Andy Gospodarek wrote:
> I booted an igb kernel with the option pci=nomsi and instantly noticed
> that interrupts no longer worked on my igb device.  I took a look at the
> interrupt initialization and quickly discovered a comment stating:
> 
> "DO NOT USE EIAME or IAME in legacy mode"
> 
> It seemed a bit odd that bits to enable IAM were being set in legacy
> interrupt mode, so I dropped out the following parts and interrupts
> began working fine again.
> 
> Signed-off-by: Andy Gospodarek <andy@greyhouse.net>
> ---
> 
>  igb_main.c |    3 ---
>  1 files changed, 3 deletions(-)
> 
> diff --git a/drivers/net/igb/igb_main.c b/drivers/net/igb/igb_main.c
> index f3c144d..be5da09 100644
> --- a/drivers/net/igb/igb_main.c
> +++ b/drivers/net/igb/igb_main.c
> @@ -472,9 +471,6 @@ static int igb_request_irq(struct igb_adapter *adapter)
>  		goto request_done;
>  	}
>  
> -	/* enable IAM, auto-mask */
> -	wr32(E1000_IAM, IMS_ENABLE_MASK);
> -

ACK from Auke?  (apologies if I missed it...)

Re: [PATCH 2.6.25] igb: fix legacy mode irq issue

[Kok, Auke]

Jeff Garzik wrote:
> Andy Gospodarek wrote:
>> I booted an igb kernel with the option pci=nomsi and instantly noticed
>> that interrupts no longer worked on my igb device.  I took a look at the
>> interrupt initialization and quickly discovered a comment stating:
>>
>> "DO NOT USE EIAME or IAME in legacy mode"
>>
>> It seemed a bit odd that bits to enable IAM were being set in legacy
>> interrupt mode, so I dropped out the following parts and interrupts
>> began working fine again.
>>
>> Signed-off-by: Andy Gospodarek <andy@greyhouse.net>
>> ---
>>
>>  igb_main.c |    3 ---
>>  1 files changed, 3 deletions(-)
>>
>> diff --git a/drivers/net/igb/igb_main.c b/drivers/net/igb/igb_main.c
>> index f3c144d..be5da09 100644
>> --- a/drivers/net/igb/igb_main.c
>> +++ b/drivers/net/igb/igb_main.c
>> @@ -472,9 +471,6 @@ static int igb_request_irq(struct igb_adapter
>> *adapter)
>>          goto request_done;
>>      }
>>  
>> -    /* enable IAM, auto-mask */
>> -    wr32(E1000_IAM, IMS_ENABLE_MASK);
>> -
> 
> ACK from Auke?  (apologies if I missed it...)

you did not miss it yet :)

So, in principle this patch might leave interrupts enabled way too long.
Unfortunately the code to enable IAM is way too complex for upstream-fixes so I
don't want to push that into 2.6.25. I'm scrambling right now to figure out if
this patch doesn't create endless interrupts from the hardware.

Once I'm happy with that answer I'll push/ack it

Auke