Re: [PATCH v3 04/17] PCI: Do not override delay for D0->D3hot transition

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On Tue, 2020-03-03 at 19:57 +0100, Rafael J. Wysocki wrote:
> > Both specifications that document mechanisms for overriding the
> > D3hot->D0 waiting time only speak of this specific direction.
> > Nothing is mentioned about the opposite (D*->D3hot) except for
> > the default value of 10ms in PCI Express Base Specification
> > r5.0 (May 22, 2019), Section 5.9 "State Transition Recovery Time
> > Requirements".
> 
> Unless you have a specific example of a system on which the current
> code doesn't work (and which should be mentioned here), I don't think
> that it is a good idea to make this change.
> 

I do not have a specific example for a failing system here. The intention
is purely to bring the code in line with what
the spec says (or in this case:
what the spec does not say).

> There are systems in which it would make a measurable difference in
> things like the time it takes to suspend the system.

This patch only affects the D0->D3hot delay within pci_pm_reset().
(I will make this more explicit in the commit title/message.)
The PM reset is only ever invoked from __pci_reset_function_locked()
and pci_probe_reset_function(). Specifically, pci_set_power_state() is untouched.
I am not well versed into the system suspend code, but unless we are resetting the
devices there, this patch should not affect system suspend time at all.



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