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Re: [PATCH V8 4/5] PCI/ASPM: save power on values during bridge init

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Bjorn,

On 4/12/2017 3:19 PM, Rajat Jain wrote:
> On Fri, Apr 7, 2017 at 9:55 PM, Sinan Kaya <okaya@codeaurora.org> wrote:
>> Now that we added a hook to be called from device_add, save the
>> default values from the HW registers early in the boot for further
>> reuse during hot device add/remove operations.
>>
>> If the link is down during boot, assume that we want to enable L0s
>> and L1 following hotplug insertion as well as L1SS if supported.
> 
> IIUC, so far POLICY_DEFAULT meant that we'd just use & follow what
> BIOS has done, and play it safe (never try to be more opportunistic).
> With this change however, we'd be slightly overstepping and giving
> ourselves benefit of doubt if the BIOS could not enable ASPM states
> because the link was not up. This may be good, but I think we should
> call it out, and add some more elaborate comment on the POLICY_DEFAULT
> description (what to, and what not to expect in different situations).
> 
> It is important because existing systems today, that used to boot
> without cards and later hotplugged them, didn't have ASPM states
> enabled. They will now suddenly start seeing all ASPM states enabled
> including L1 substates for the first time (if supported).
> 

Rajat has a good point here. Would you like me to update the ASPM document
with this new behavior for hotplug?

Do you have another behavior preference when it comes this?

Sinan

-- 
Sinan Kaya
Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.

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Re: [PATCH V8 4/5] PCI/ASPM: save power on values during bridge init Rajat Jain <rajatja@google.com> - 2017-04-12 21:20 +0200
  Re: [PATCH V8 4/5] PCI/ASPM: save power on values during bridge init Sinan Kaya <okaya@codeaurora.org> - 2017-04-14 21:20 +0200
    Re: [PATCH V8 4/5] PCI/ASPM: save power on values during bridge init Bjorn Helgaas <helgaas@kernel.org> - 2017-04-14 23:50 +0200
      Re: [PATCH V8 4/5] PCI/ASPM: save power on values during bridge init Sinan Kaya <okaya@codeaurora.org> - 2017-04-15 00:20 +0200
        Re: [PATCH V8 4/5] PCI/ASPM: save power on values during bridge init Bjorn Helgaas <bhelgaas@google.com> - 2017-04-17 18:40 +0200
          Re: [PATCH V8 4/5] PCI/ASPM: save power on values during bridge init Sinan Kaya <okaya@codeaurora.org> - 2017-04-17 20:00 +0200
            RE: [PATCH V8 4/5] PCI/ASPM: save power on values during bridge init "Patel, Mayurkumar" <mayurkumar.patel@intel.com> - 2017-04-21 09:50 +0200
              Re: [PATCH V8 4/5] PCI/ASPM: save power on values during bridge init Sinan Kaya <okaya@codeaurora.org> - 2017-04-21 16:00 +0200
                RE: [PATCH V8 4/5] PCI/ASPM: save power on values during bridge init "Patel, Mayurkumar" <mayurkumar.patel@intel.com> - 2017-04-21 16:20 +0200

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