From: Yijing Wang <wangyijing@huawei.com>
To: Bjorn Helgaas <bhelgaas@google.com>, Keith Busch <keith.busch@intel.com>
Cc: "linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
Jordan Hargrave <Jordan_Hargrave@dell.com>,
Jon Mason <jon.mason@intel.com>, Jon Mason <jdmason@kudzu.us>
Subject: Re: [PATCH] PCI: update device mps when doing pci hotplug
Date: Thu, 25 Sep 2014 09:23:07 +0800 [thread overview]
Message-ID: <54236E7B.5000905@huawei.com> (raw)
In-Reply-To: <CAErSpo5upA7KYVo=_SvwJ9pdNot_5ENi3OtiPpuzZjpwj3ghPA@mail.gmail.com>
On 2014/9/25 7:30, Bjorn Helgaas wrote:
> On Wed, Sep 24, 2014 at 4:41 PM, Keith Busch <keith.busch@intel.com> wrote:
>> Just poking this thread to make sure it's not dead. :)
>>
>> I tested Yijing's proposal and it is successful on our Intel server
>> platforms; hoping either this or something that derives similar behavior
>> will be applied so we can remove bus tuning kernel parameters.
>>
>> Tested-by: Keith Busch <keith.busch@intel.com>
>
> Oops, thanks for poking me, because this was indeed dead.
>
> My main objection was to testing "is_hotplug_bridge". That doesn't
> seem right, because this issue really isn't specific to hotplug. I
> didn't see a resolution of that, but let me know if I missed it.
Why I introduced "is_hotplug_bridge" is to avoid to touch the MPS which is not
in hotplug case when pcie_bus_config == PCIE_BUS_TUNE_OFF.
It's so sad that PCIe spec doesn't give a detailed guide to configure MPS.
I'd like to refactor current MPS framework, but now there are still some puzzles
to me. I need to have a deeper understanding of pcie mps. I read Jon's mps patch
log from git, I found he turn off all this MPS config, because some issues were found
in some platforms, but no platforms detailed info and no bugzilla records.
>
> Bjorn
>
>> On Thu, 4 Sep 2014, Yijing Wang wrote:
>>>>>>>
>>>>>>> if (pcie_bus_config == PCIE_BUS_TUNE_OFF) {
>>>>>>> + pcie_bus_update_set(dev);
>>>>>>
>>>>>>
>>>>>> You're only adding this to the PCIE_BUS_TUNE_OFF path. Can't the same
>>>>>> problem occur for other pcie_bus_config settings?
>>>>>
>>>>>
>>>>> We only found the problem during PCIE_BUS_TUNE_OFF set. Other mode like
>>>>> PCIE_BUS_SAFE and PCIE_BUS_PEER2PEER.
>>>>> This issue won't happen.
>>>>
>>>>
>>>> Sorry, I can't parse this. Are you saying the problem won't happen in
>>>> the other modes? Why not?
>>>
>>>
>>> Hi Bjorn, when in PCIE_BUS_SAFE mode, pcie_find_smpss() will find the
>>> largest available mpss in a pcie path.
>>> Then call pcie_bus_configure_set() to set all devices' mps to the largest
>>> available mps in this path, so
>>> all devices in the path will have the same mps. When in
>>> PCIE_BUS_PEER2PEER, all devices' mps will be set to 128B
>>> for safety. And to the PCIE_BUS_PERFORMANCE mode, I found Jon's comment in
>>> pcie_write_mps(),
>>>
>>> /* For "Performance", the assumption is made that
>>> * downstream communication will never be larger
>>> than
>>> * the MRRS. So, the MPS only needs to be
>>> configured
>>> * for the upstream communication. This being the
>>> case, <------
>>> * walk from the top down and set the MPS of the
>>> child
>>> * to that of the parent bus.
>>>
>>> So I think the problem won't happen in other modes.
>>>
>>> Thanks!
>>> Yijing.
>>>
>>>
>>>>
>>>>>>> pcie_bus_detect_mps(dev);
>>>>>>> return 0;
>>>>>>> }
>>>>
>>>>
>>>> .
>>>>
>>>
>>>
>>> --
>>> Thanks!
>>> Yijing
>>>
>>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-pci" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at http://vger.kernel.org/majordomo-info.html
>
> .
>
--
Thanks!
Yijing
next prev parent reply other threads:[~2014-09-25 1:23 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-07-29 8:17 [PATCH] PCI: update device mps when doing pci hotplug Yijing Wang
2014-07-29 16:18 ` Alex Williamson
2014-07-29 16:30 ` Keith Busch
2014-07-29 16:42 ` Alex Williamson
2014-07-29 19:04 ` Keith Busch
2014-07-30 3:35 ` Yijing Wang
2014-07-30 3:27 ` Yijing Wang
2014-07-30 3:33 ` Ethan Zhao
2014-07-30 3:42 ` Yijing Wang
2014-07-30 3:58 ` Ethan Zhao
2014-07-30 4:42 ` Yijing Wang
2014-07-30 6:26 ` Ethan Zhao
2014-07-30 6:57 ` Yijing Wang
2014-07-30 7:17 ` Ethan Zhao
2014-07-30 8:13 ` Yijing Wang
2014-07-30 8:38 ` Ethan Zhao
2014-07-30 9:17 ` Yijing Wang
2014-07-30 19:41 ` Jordan_Hargrave
2014-09-03 19:20 ` Bjorn Helgaas
2014-09-03 22:42 ` Bjorn Helgaas
2014-09-04 6:12 ` Yijing Wang
2014-09-04 13:16 ` Bjorn Helgaas
2014-09-05 1:27 ` Yijing Wang
2014-09-05 14:37 ` Keith Busch
2014-09-24 22:41 ` Keith Busch
2014-09-24 23:30 ` Bjorn Helgaas
2014-09-25 1:23 ` Yijing Wang [this message]
2014-09-25 16:46 ` Keith Busch
2014-09-26 3:22 ` Yijing Wang
2014-10-02 15:31 ` Jordan_Hargrave
-- strict thread matches above, loose matches on Subject: below --
2014-07-29 8:23 Yijing Wang
2013-02-05 3:55 Yijing Wang
2013-05-28 3:15 ` Yijing Wang
2013-07-29 23:33 ` Bjorn Helgaas
2013-07-30 3:20 ` Yijing Wang
2013-07-30 3:42 ` Bjorn Helgaas
2013-07-30 22:29 ` Bjorn Helgaas
2013-07-31 9:15 ` Yijing Wang
2013-07-31 17:53 ` Bjorn Helgaas
2013-07-31 20:42 ` Bjorn Helgaas
2013-08-01 1:23 ` Yijing Wang
2013-08-01 1:21 ` Yijing Wang
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