linux-kernel - Re: How long should be PCIe card in Warm Reset state?

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Date:   Tue, 30 Mar 2021 17:04:58 +0200
From:   Pali Rohár <pali@...nel.org>
To:     "Maciej W. Rozycki" <macro@...am.me.uk>
Cc:     David Laight <David.Laight@...LAB.COM>,
        'Amey Narkhede' <ameynarkhede03@...il.com>,
        "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
        "helgaas@...nel.org" <helgaas@...nel.org>,
        "lorenzo.pieralisi@....com" <lorenzo.pieralisi@....com>,
        "kabel@...nel.org" <kabel@...nel.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "raphael.norwitz@...anix.com" <raphael.norwitz@...anix.com>
Subject: Re: How long should be PCIe card in Warm Reset state?

On Tuesday 30 March 2021 16:34:47 Maciej W. Rozycki wrote:
> On Tue, 30 Mar 2021, Pali Rohár wrote:
> 
> > >  If I were to implement this stuff, for good measure I'd give it a safety 
> > > margin beyond what the spec requires and use a timeout of say 2-4s while 
> > > actively querying the status of the device.  The values given in the spec 
> > > are only the minimum requirements.
> > 
> > Are you able to also figure out what is the minimal timeout value for 
> > PCIe Warm Reset?
> > 
> > Because we are having troubles to "decode" correct minimal timeout value
> > for this PCIe Warm Reset (not Function-level reset).
> 
>  The spec does not give any exceptions AFAICT as to the timeouts required 
> between the three kinds of a Conventional Reset (Hot, Warm, or Cold) and 
> refers to them collectively as a Conventional Reset across the relevant 
> parts of the document, so clearly the same rules apply.
> 
>   Maciej

There are specified more timeouts related to Warm reset and PERST#
signal. Just they are not in Base spec, but in CEM spec. See previous
Amey's email where are described some timeouts and also links in my
first email where I put other timeouts defined in specs relevant for
PERST# signal and therefore also for Warm Reset.