linux-kernel - Re: [PATCH v4 0/9] PCI/PM: Always disable PTM for all devices during suspend

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Date:   Mon, 12 Sep 2022 15:32:16 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Rajvi Jingar <rajvi.jingar@...ux.intel.com>
Cc:     Koba Ko <koba.ko@...onical.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        "David E . Box" <david.e.box@...ux.intel.com>,
        Sathyanarayanan Kuppuswamy 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        linux-pci@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Bjorn Helgaas <bhelgaas@...gle.com>,
        Kai-Heng Feng <kai.heng.feng@...onical.com>,
        "Rafael J . Wysocki" <rafael@...nel.org>
Subject: Re: [PATCH v4 0/9] PCI/PM: Always disable PTM for all devices during
 suspend

On Mon, Sep 12, 2022 at 01:15:59PM -0700, Rajvi Jingar wrote:
> On 9/9/22 13:24, Bjorn Helgaas wrote:
> > From: Bjorn Helgaas<bhelgaas@...gle.com>
> > 
> > We currently disable PTM for Root Ports during suspend.  Leaving PTM
> > enabled for downstream devices causes UR errors if they send PTM Requests
> > to upstream devices that have PTM disabled.
> > 
> > The intent of this series is to:
> > 
> >    - Unconditionally disable PTM during suspend (even if the driver saves
> >      its own state) by moving the disable from pci_prepare_to_sleep() to
> >      pci_pm_suspend().
> > 
> >    - Disable PTM for all devices by removing the Root Port condition and
> >      doing it early in the suspend paths.
> > 
> >    - Explicitly re-enable PTM during resume.
> > 
> > Changes between v3 and v4:
> >    - Use u16 for ptm_cap
> >    - Add kernel-doc for pci_enable_ptm() and pci_disable_ptm() (exported
> >      functions)
> >    - Drop "Preserve PTM Root Select" (unnecessary since enabling PTM sets
> >      Root Select when needed)
> >    - Squash these three patches into one because they make more sense that
> >      way:
> > 	PCI/PTM: Add suspend/resume
> > 	PCI/PTM: Add pci_enable_ptm() wrapper
> > 	PCI/PTM: Add pci_disable_ptm() wrapper
> >    - Add "PCI/PTM: Preserve RsvdP bits in PTM Control register"
> >    - Add "PCI/PTM: Consolidate PTM interface declarations"
> > 
> > Bjorn Helgaas (9):
> >    PCI/PTM: Cache PTM Capability offset
> >    PCI/PTM: Add pci_upstream_ptm() helper
> >    PCI/PTM: Separate configuration and enable
> >    PCI/PTM: Add pci_suspend_ptm() and pci_resume_ptm()
> >    PCI/PTM: Move pci_ptm_info() body into its only caller
> >    PCI/PTM: Preserve RsvdP bits in PTM Control register
> >    PCI/PTM: Reorder functions in logical order
> >    PCI/PTM: Consolidate PTM interface declarations
> >    PCI/PM: Always disable PTM for all devices during suspend
> 
> Looks good. It fixes the issue on Dell Precision 5530 with Coffee Lake
> CPU platforms to get improved residency in low power idle states.
> 
> Tested-by:rajvi.jingar@...ux.intel.com

Thanks a lot for testing this!

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Bjorn