Re: One problem in reassign pci bus number?
From: Richard Yang
Date: Mon May 14 2012 - 02:46:29 EST
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@xxxxxxxxxxxxxxxxxx> 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.
>>>>
>>>>So in pci_scan_bridge(), B3 will be met in the second pass and get bus
>>>>number 16?
>>>
>> Yinghai,
>>
>> 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.
>
>if B3 is only bridge on Bus1, it probe_resource should return [2,15]
>at first, and then scan B3.
>
>Yinghai
--
Richard Yang
Help you, Help me
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