linux-kernel - Re: [PATCH v2 1/9] PCI/PME: Drop unused support for PMEs from Root Complex Event Collectors

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Date:   Mon, 21 Nov 2016 23:58:09 +0100
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Lukas Wunner <lukas@...ner.de>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/9] PCI/PME: Drop unused support for PMEs from Root Complex Event Collectors

On Monday, November 21, 2016 04:42:10 PM Bjorn Helgaas wrote:
> On Mon, Nov 21, 2016 at 11:28:56PM +0100, Rafael J. Wysocki wrote:
> > On Monday, November 21, 2016 03:45:19 PM Bjorn Helgaas wrote:
> > > Since we register pcie_pme_driver only for PCI_EXP_TYPE_ROOT_PORT, the PME
> > > driver never claims Root Complex Event Collectors.
> > > 
> > > Remove unused code related to Root Complex Event Collectors.
> > > 
> > > Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>
> > > ---
> > >  drivers/pci/pcie/pme.c |   17 +----------------
> > >  1 file changed, 1 insertion(+), 16 deletions(-)
> > > 
> > > diff --git a/drivers/pci/pcie/pme.c b/drivers/pci/pcie/pme.c
> > > index 884bad5..9e8aa9d 100644
> > > --- a/drivers/pci/pcie/pme.c
> > > +++ b/drivers/pci/pcie/pme.c
> > > @@ -319,23 +319,8 @@ static int pcie_pme_set_native(struct pci_dev *dev, void *ign)
> > >  static void pcie_pme_mark_devices(struct pci_dev *port)
> > >  {
> > >  	pcie_pme_set_native(port, NULL);
> > > -	if (port->subordinate) {
> > > +	if (port->subordinate)
> > >  		pci_walk_bus(port->subordinate, pcie_pme_set_native, NULL);
> > > -	} else {
> > > -		struct pci_bus *bus = port->bus;
> > > -		struct pci_dev *dev;
> > > -
> > > -		/* Check if this is a root port event collector. */
> > > -		if (pci_pcie_type(port) != PCI_EXP_TYPE_RC_EC || !bus)
> > > -			return;
> > > -
> > > -		down_read(&pci_bus_sem);
> > > -		list_for_each_entry(dev, &bus->devices, bus_list)
> > > -			if (pci_is_pcie(dev)
> > > -			    && pci_pcie_type(dev) == PCI_EXP_TYPE_RC_END)
> > > -				pcie_pme_set_native(dev, NULL);
> > > -		up_read(&pci_bus_sem);
> > > -	}
> > >  }
> > >  
> > >  /**
> > 
> > Acked-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> I'm shocked :)

Well, the code is not used as a matter of fact and it can be added back
when needed, can't it?

> You mean we really don't care about PME from RC event
> collectors?  Without the RCEC support, we won't see any PMEs from RC
> integrated devices.  I mean, I don't think we see those PMEs today, but I
> thought maybe we would *want* to.  No?

In the majority of cases those are signaled via ACPI GPEs anyway.  I'm not
sure why, but event collectors have not been extremely popular for the last
several years.  I haven't seen a single one with native PME handling so far
and I kind of don't expect to see any.

Thanks,
Rafael