linux-kernel - Re: [PATCH] PCI: Disable PTM on Upstream Ports during suspend

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Date:   Wed, 31 Aug 2022 08:23:01 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:     Kai-Heng Feng <kai.heng.feng@...onical.com>,
        Koba Ko <koba.ko@...onical.com>,
        "David E . Box" <david.e.box@...ux.intel.com>,
        Sathyanarayanan Kuppuswamy 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Rajvi Jingar <rajvi.jingar@...ux.intel.com>,
        linux-pm@...r.kernel.org
Subject: Re: [PATCH] PCI: Disable PTM on Upstream Ports during suspend

[+cc Rafael, Rajvi, linux-pm]

On Wed, Aug 31, 2022 at 12:53:05PM +0300, Mika Westerberg wrote:
> On Tue, Aug 30, 2022 at 10:52:24AM -0500, Bjorn Helgaas wrote:
> > +	type = pci_pcie_type(dev);
> > +	if (!(type == PCI_EXP_TYPE_ROOT_PORT ||
> > +	      type == PCI_EXP_TYPE_UPSTREAM ||
> > +	      type == PCI_EXP_TYPE_ENDPOINT))
> > +		return;
> 
> Perhaps switch () instead?
> 
> switch (pci_pcie_type(dev)) {
> case PCI_EXP_TYPE_ROOT_PORT:
> case PCI_EXP_TYPE_UPSTREAM:
> case PCI_EXP_TYPE_ENDPOINT:
> 	break;
> default:
> 	return;
> }
> 
> Either way,
> 
> Reviewed-by: Mika Westerberg <mika.westerberg@...ux.intel.com>

Thanks!  I dropped this patch for now.  I think Rajvi's similar
patch [1] is much better because we only need this kind of check in
one place -- where we enable PTM.

Also, we need to tighten this up so we *always* disable PTM [2].  The
patch I posted still calls pci_disable_ptm() from
pci_prepare_to_sleep(), which means we only do it when
!pdev->state_saved, so we leave PTM enabled if the driver saves its
own state.

Bjorn

[1] https://lore.kernel.org/r/20220830104913.1620539-2-rajvi.jingar@linux.intel.com
[2] https://lore.kernel.org/r/CAJZ5v0iHckqia4OywKzSNWFCaq7eOkJcm5yXJdT2_sNdd36gDw@mail.gmail.com