linux-kernel - Re: One problem in reassign pci bus number?

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Date:	Wed, 16 May 2012 09:18:34 +0800
From:	Richard Yang <weiyang@...ux.vnet.ibm.com>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	Richard Yang <weiyang@...ux.vnet.ibm.com>,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: One problem in reassign pci bus number?

On Tue, May 15, 2012 at 10:32:46AM -0700, Yinghai Lu wrote:
>On Sun, May 13, 2012 at 11:46 PM, Richard Yang
><weiyang@...ux.vnet.ibm.com> wrote:
>> On Sun, May 13, 2012 at 10:40:41PM -0700, Yinghai Lu wrote:
>>>On Sun, May 13, 2012 at 6:55 PM, Richard Yang
>>><weiyang@...ux.vnet.ibm.com> wrote:
>>>> On Mon, Apr 23, 2012 at 03:46:03PM -0400, Don Dutile wrote:
>>>>>On 04/22/2012 11:52 AM, Richard Yang wrote:
>>>>>>All,
>>>>>>
>>>>>>I am reading the pci_scan_bridge() and not sure what will happen in
>>>>>>following situation.
>>>>>>
>>>>>>Suppose the kernel is not passed the pci=assign-busses.
>>>>>>
>>>>>>Below is a picture about the pci system.
>>>>>>
>>>>>>                    +-------+
>>>>>>                    |       | root bridge(0,255)
>>>>>>                    +---+---+
>>>>>>                        |          Bus 0
>>>>>>       -----+-----------+------------------------------+--
>>>>>>            |                                          |
>>>>>>            |                                          |
>>>>>>            |                                          |
>>>>>>       +----+----+                               +-----+-----+
>>>>>>       |         |  B1(1,15)                     |           |B2(16,28)
>>>>>>       +----+----+                               +-----+-----+
>>>>>>            |  Bus 1                                   |    Bus 16
>>>>>>       -----+-----------------------         ----------+----------------
>>>>>>                             |
>>>>>>                        +----+----+
>>>>>>                        |         | B3
>>>>>>                        +---------+
>>>>>>
>>>>>>Suppose B1 and B2 works fine with the BIOS, which get the right bus
>>>>>>number and range.
>>>>>>
>>>>>>B3 does not works fine with the BIOS, which doesn't get the bus number.
>>>>>>
>>>> Take my original question.
>>>>
>>>> B3 doesn't get the bus number, which its parent doesn't have free bus
>>>> number and there is no gap between B1 and B2.
>>>>
>>>> So in this case, the probe_resource() can't find bus number for B3.
>>>> Then cause pci_bridge_probe_busn_res() return non-zero.
>>>>
>>>> Then B3 couldn't work fine?
>>>
>>>B3 is on Bus 1? B3 is the one of bridges on Bus1?
>> No,  I omit other bridges on Bus#1.
>> They will occupy bus number 2-15, which is calculated by BIOS and set to
>> bridge's configuration space.
>
>with that new condition, probe_resource will return zero.
>
>for those kind of case:
>1. use echo 1 > /sys .../remove to remove devices under Bridge2.
>2. use setpci to change bus register of bridge2 to move high to make
>more space for bridge 1.
>3. rescan bridge 1 and bridge 2.
So these steps is done after boot up and user find B3 doesn't work?
>
>Yinghai

-- 
Richard Yang
Help you, Help me

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