Re: [RFC][PATCH 0/2] SN platform needs platform_irq_to_vector?

[Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>]

Hi John,

John Keller wrote:
>> Hi,
>>
>> This is FYI.
>>
>> If VECTOR_DOMAIN_PERCPU is NOT enabled:
>>
>> The "irq = vector" is always true in the following cases:
>>     - reserve_irq_vector(), which is used only by SN
>>     - create_irq() used on the system that has NO I/O SAPIC
> 
> Could you say a bit more about this case. I see create_irq()
> calling find_unassigned_vector() and find_unassigned_irq().
> How is "irq = vector" guaranteed to be always true in this case?

It's guaranteed as follows:

- When find_unassigned_vector()/find_unassigned_irq() search
   available vector and irq, it always start to search from
   IA64_FIRST_DEVICE_VECTOR.

- clear_irq_vector() releases both vector and irq.

Thanks,
Yasuaki

> John
> 
> 
> 
>>     - assign_irq_vector() with AUTO_ASSIGN specified
>>     - Vectors outside FIRST_DEVICE_VECTOR to LAST_DEVICE_VECTOR
>>
>> The "irq = vector" is not always true in the folliwng cases:
>>     - create_irq() used on the system that has I/O SAPICs.
>>     - assign_irq_vector() with the value other than AUTO_ASSIGN
>>       specified on the system has I/O SAPICs.
>>
>> And it is not ensured that those are true even in the future.
>>
>> Yasuaki, could you check if it is correct?
>>
>> Thanks,
>> Kenji Kaneshige
>>
>>
>>
>> 2007-08-02 (木) の 08:26 -0500 に John Keller さんは書きました:
>>> Yes, we'll take a look at it.
>>>
>>> John
>>>
>>>
>>>> Hi Kenji-san
>>>>
>>>> I believe we need this property, but I am not 100% sure, so I am
>>>> going to forward your patch to our team who maintain the IRQ code
>>>> for Altix.
>>>>
>>>> Mike, Aaron or John, would one of you have time to take a look at
>>>> this?
>>>>
>>>> Thanks,
>>>> Jes
>>>>
>>>>
>>>> Kenji Kaneshige wrote:
>>>>> Hi Jes-san, Russ-san, Christoph-san and SN platform developers,
>>>>>
>>>>> I glanced over the SN code, and I found SN platform doesn't have SN
>>>>> specific irq_to_vector() function, though it has SN specific
>>>>> local_vector_to_irq() function. I guess it was OK because maybe SN
>>>>> platform depends on irq = vector and old generic irq_to_vector() was
>>>>> just returning the same value as irq.
>>>>>
>>>>> The irq_to_vector() function, however, has been changed by vector
>>>>> domain support, and currently it can return the different value from
>>>>> irq, even when VECTOR_DOMAIN_PERCPU is not enabled. This can happen
>>>>> when an interrupt thorough I/O SAPIC is unregistered and another
>>>>> interupt is registered. So if my guess (SN platform depends on irq =
>>>>> vector) is true, something problem might happen on SN platform when
>>>>> PCI hotplugging or driver reloading.
>>>>>
>>>>> If it is true that SN platform depends on irq = vector, we need to
>>>>> implement SN specific irq_to_vector() that returns the same value as
>>>>> irq, I think. I made sample patches to implement platform specific
>>>>> irq_to_vector() as follows. Note that [PATCH 2/2] is not tested yet
>>>>> because I don't have any SN platform unfortunately.
>>>>>
>>>>>     [PATCH 1/2] Add base support for platform_irq_to_vector()
>>>>>     [PATCH 2/2] Implement platform_irq_to_vector() for SN
>>>>>
>>>>> Could you give me comments?
>>>>>
>>>>> Thanks,
>>>>> Kenji Kaneshige
>>>>>
>>>>
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