Re: [RFC PATCH] PCIe: Add PCIe runtime D3cold support

[huang ying]

On Wed, Apr 18, 2012 at 4:20 AM, Rafael J. Wysocki <rjw@xxxxxxx> wrote:
> On Tuesday, April 17, 2012, huang ying wrote:
>> On Tue, Apr 17, 2012 at 1:07 AM, Rafael J. Wysocki <rjw@xxxxxxx> wrote:
>> > Moreover, I really don't think it's a good idea to put PCI Express ports into
>> > low-power states in general. ÂIt might work on your platform, whatever it is,
>> > but that doesn't mean it's going to work on every PCI Express system out
>> > there. ÂI actually know of a number of such systems where it surely won't
>> > work at all.
>>
>> The runtime PM support for PCIe port is not turned on by default, we need
>>
>> # echo auto > /sys/devices/pcixxxx:xx/<pci id>/power/control
>>
>> to turn on it. ÂAnd we will turn on it on system it works. ÂIs this sufficient?
>
> No, it is not. ÂIn some cases it shouldn't be enabled at all for PCI Express
> ports, as far as I can say, so to be on the safe side we should only enable it
> on platforms where PCI Express ports are known to work correctly with runtime PM.

Sorry, I did not catch your idea exactly.  I think disable it by
default and enable it by sysfs interface is what you suggested, isn't
it?  Or you suggest something like "white list"?

Best Regards,
Huang Ying
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