linux-kernel - Re: [PATCH] PCI: Document PCIE BUS MPS parameters

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Date:	Wed, 23 Jan 2013 18:13:02 +0800
From:	Yijing Wang <wangyijing0307@...il.com>
To:	Andrew Murray <andrew.murray@....com>
CC:	Yijing Wang <wangyijing@...wei.com>, Rob Landley <rob@...dley.net>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Jon Mason <jdmason@...zu.us>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	Hanjun Guo <guohanjun@...wei.com>,
	"jiang.liu@...wei.com" <jiang.liu@...wei.com>
Subject: Re: [PATCH] PCI: Document PCIE BUS MPS parameters

于 2013-01-23 17:21, Andrew Murray 写道:
> On Wed, Jan 23, 2013 at 08:01:36AM +0000, Yijing Wang wrote:
>> Document PCIE BUS MPS parameters pcie_bus_tune_off, pcie_bus_safe,
>> pcie_bus_peer2peer, pcie_bus_perf into Documentation/kernel-parameters.txt.
>> These parameters were introduced by Jon Mason <mason@...i.com> at
>> commit 5f39e6705 and commit b03e7495a8. Document these into 
>> kernel-parameters.txt help users to understand and use the parameters.
>>
>> Signed-off-by: Yijing Wang <wangyijing@...wei.com>
>> ---
>>  Documentation/kernel-parameters.txt |   13 +++++++++++++
>>  1 files changed, 13 insertions(+), 0 deletions(-)
>>
>> diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
>> index 363e348..4dfa8d2 100644
>> --- a/Documentation/kernel-parameters.txt
>> +++ b/Documentation/kernel-parameters.txt
>> @@ -2227,6 +2227,19 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
>>  				This sorting is done to get a device
>>  				order compatible with older (<= 2.4) kernels.
>>  		nobfsort	Don't sort PCI devices into breadth-first order.
>> +		pcie_bus_tune_off	[X86] Disable PCI-E MPS turning and using
>> +				the BIOS configured MPS defaults.
>> +		pcie_bus_safe	[X86] Use the smallest common denominator MPS
>> +				of the entire tree below a root complex for every device
>> +				on that fabric. Can avoid inconsistent mps problem caused
>> +				by hotplug.
>> +		pcie_bus_perf	[X86] Configure pcie device MPS to the largest
>> +				allowable MPS based on its parent bus.Improve performance
>> +				as much as possible.
>> +		pcie_bus_peer2peer	[X86] Make the system wide MPS the smallest
>> +				possible value (128B).This configuration could prevent it
>> +				from working by having the MPS on one root port different
>> +				than the MPS on another.
>>  		cbiosize=nn[KMG]	The fixed amount of bus space which is
>>  				reserved for the CardBus bridge's IO window.
>>  				The default value is 256 bytes.
>>
> I was searching for documentation on this the other day.
> 
> It's not just X86 that use these options, PowerPC and Tile also use them (grep
> for users of pcie_bus_configure_settings). I've also noticed a call to it from
> hotplug as well...

Hi Andrew,
   Thanks for reminder! I will update this patch right now.

> 
> In addition these options also have an effect on MRRS - I've not figured out
> what effect they have, but you can look in drivers/pci/probe.c at the
> pcie_write_mrrs function.

This is a separate issue, Andrew, can you provide the effetct problem log or detail information?
That will helps us to analyze this issue.

> 
> Andrew Murray
>  
> 
> --
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