linux-kernel - Re: [PATCH v5 2/5] PCI: Check PCI_PM_CTRL instead of PCI_COMMAND in pci_dev

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Message-ID: <20240903213240.GA304079@bhelgaas>
Date: Tue, 3 Sep 2024 16:32:40 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Mario Limonciello <mario.limonciello@....com>
Cc: Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Gary Li <Gary.Li@....com>, Mario Limonciello <superm1@...nel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Mathias Nyman <mathias.nyman@...el.com>,
	"open list : PCI SUBSYSTEM" <linux-pci@...r.kernel.org>,
	open list <linux-kernel@...r.kernel.org>,
	"open list : USB XHCI DRIVER" <linux-usb@...r.kernel.org>,
	Daniel Drake <drake@...lessos.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Subject: Re: [PATCH v5 2/5] PCI: Check PCI_PM_CTRL instead of PCI_COMMAND in
 pci_dev_wait()

On Tue, Sep 03, 2024 at 01:32:30PM -0500, Mario Limonciello wrote:
> On 9/3/2024 13:25, Bjorn Helgaas wrote:
> > On Tue, Sep 03, 2024 at 12:31:00PM -0500, Mario Limonciello wrote:
> > > On 9/3/2024 12:11, Bjorn Helgaas wrote:
> > > ...
> > 
> > > >     8) The USB4 stack sees the device and assumes it is in D0, but it
> > > >     seems to still be in D3cold.  What is this based on?  Is there a
> > > >     config read that returns ~0 data when it shouldn't?
> > > 
> > > Yes there is.  From earlier in the thread I have a [log] I shared.
> > > 
> > > The message emitted is from ring_interrupt_active():
> > > 
> > > "thunderbolt 0000:e5:00.5: interrupt for TX ring 0 is already enabled"
> > 
> > Right, that's in the cover letter, but I can't tell from this what the
> > ioread32(ring->nhi->iobase + reg) returned.  It looks like this is an
> > MMIO read of BAR 0, not a config read.
> 
> Yeah.  I suppose another way to approach this problem is to make something
> else in the call chain poll PCI_PM_CTRL.
> 
> Polling at the start of nhi_runtime_resume() should also work.  For the
> "normal" scenario it would just be a single read to PCI_PM_CTRL.

It doesn't sound like this is anything specific to Thunderbolt, so
there should be a generic solution.