linux-kernel - Re: [PATCH v3 -tip 5/5] AHCI: Support multiple MSIs

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Message-ID: <506A723B.6040504@pobox.com>
Date:	Tue, 02 Oct 2012 00:48:59 -0400
From:	Jeff Garzik <jgarzik@...ox.com>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
CC:	Alexander Gordeev <agordeev@...hat.com>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	Yinghai Lu <yinghai@...nel.org>,
	Matthew Wilcox <willy@...ux.intel.com>, x86@...nel.org,
	linux-pci@...r.kernel.org, linux-ide@...r.kernel.org
Subject: Re: [PATCH v3 -tip 5/5] AHCI: Support multiple MSIs

On 10/02/2012 12:21 AM, Bjorn Helgaas wrote:
> On Mon, Oct 1, 2012 at 9:04 PM, Jeff Garzik <jgarzik@...ox.com> wrote:
>> On 10/01/2012 04:13 AM, Alexander Gordeev wrote:
>>>
>>> Take advantage of multiple MSIs implementation on x86 - on systems with
>>> IRQ remapping AHCI ports not only get assigned separate MSI vectors -
>>> but also separate IRQs. As result, interrupts generated by different
>>> ports could be serviced on different CPUs rather than on a single one.
>>>
>>> In cases when number of allocated MSIs is less than requested the Sharing
>>> Last MSI mode does not get used, no matter implemented in hardware or not.
>>> Instead, the driver assumes the advantage of multiple MSIs is negated and
>>> falls back to the single MSI mode as if MRSM bit was set (some Intel chips
>>> implement this strategy anyway - MRSM bit gets set even if the number of
>>> allocated MSIs exceeds the number of implemented ports).
>>>
>>> Signed-off-by: Alexander Gordeev <agordeev@...hat.com>
>>> ---
>>>    drivers/ata/ahci.c    |   91 ++++++++++++++++++++++++++++++++++++--
>>>    drivers/ata/ahci.h    |    6 +++
>>>    drivers/ata/libahci.c |  118
>>> ++++++++++++++++++++++++++++++++++++++++++++++---
>>>    3 files changed, 205 insertions(+), 10 deletions(-)
>>
>>
>> Acked-by: Jeff Garzik <jgarzik@...hat.com>
>>
>> Normally, this amount of changes would -really- need to go through the
>> libata tree.  However, given the amount of dependencies, it either needs a
>> merge tree or to go through the PCI tree...?
>>
>> Any maintainer comments on disposition?
>
> For what it's worth, the bulk of this change is outside PCI, so it
> doesn't seem to me like it should go through the PCI tree.  I think I
> did ack the part that touched PCI, and there's not much activity in
> the PCI MSI area right now, so I'm fine with it going through libata
> or whatever people think makes sense.

That works for me, too.  I'm ready to queue it, if libata tree is fine 
with people.

	Jeff




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