Re: [PATCH -v4 2/2] PCIe: Add PCIe runtime D3cold support

[Huang Ying]

On Sat, 2012-06-02 at 01:10 +0200, Rafael J. Wysocki wrote:
> On Friday, June 01, 2012, Huang Ying wrote:
> > On Thu, 2012-05-31 at 21:01 +0200, Rafael J. Wysocki wrote:
> > > On Thursday, May 31, 2012, Huang Ying wrote:
> > > > On Wed, 2012-05-30 at 23:49 +0200, Rafael J. Wysocki wrote:
> > > > > On Tuesday, May 22, 2012, Rafael J. Wysocki wrote:
> > > > > > On Friday, May 18, 2012, Huang Ying wrote:
> > > > > > > This patch adds runtime D3cold support to PCIe bus.  D3cold is the
> > > > > > > deepest power saving state for PCIe devices.  Where the main PCIe link
> > > > > > > will be powered off totally, so before the PCIe main link is powered
> > > > > > > on again, you can not access the device, even the configuration space,
> > > > > > > which is still accessible in D3hot.  Because the main PCIe link is not
> > > > > > > available, the PCI PM registers can not be used to put device into/out
> > > > > > > of D3cold state, that will be done by platform logic such as ACPI
> > > > > > > _PR3.
> > > > > > > 
> > > > > > > To support remote wake up in D3cold, aux power is supplied, and a
> > > > > > > side-band pin: WAKE# is used to notify remote wake up event, the pin
> > > > > > > is usually connected to platform logic such as ACPI GPE.  This is
> > > > > > > quite different with other power saving states, where remote wake up
> > > > > > > is notified via PME message through the PCIe main link.
> > > > > > > 
> > > > > > > PCIe devices in plug-in slot usually has no direct platform logic, for
> > > > > > > example, there is usually no ACPI _PR3 for them.  The D3cold support
> > > > > > > for these devices can be done via the PCIe port connected to it.  When
> > > > > > > power on/off the PCIe port, the corresponding PCIe devices are powered
> > > > > > > on/off too.  And the remote wake up event from PCIe device will be
> > > > > > > notified to the corresponding PCIe port.
> > > > > > > 
> > > > > > > The PCI subsystem D3cold support and corresponding ACPI platform
> > > > > > > support is implemented in the patch.  Including the support for PCIe
> > > > > > > devices in plug-in slot.
> > > > > > > 
> > > > > > > For more information about PCIe D3cold and corresponding ACPI support,
> > > > > > > please refer to:
> > > > > > > 
> > > > > > > - PCI Express Base Specification Revision 2.0
> > > > > > > - Advanced Configuration and Power Interface Specification Revision 5.0
> > > > > > > 
> > > > > > > Originally-by: Zheng Yan <zheng.z.yan@xxxxxxxxx>
> > > > > > > Signed-off-by: Huang Ying <ying.huang@xxxxxxxxx>
> > > > > > 
> > > > > > Reviewed-by: Rafael J. Wysocki <rjw@xxxxxxx>
> > > > > 
> > > > > On a second thought ...
> > > > > 
> > > > > > > ---
> > > > > > >  drivers/pci/pci-acpi.c         |   23 +++++++-
> > > > > > >  drivers/pci/pci-driver.c       |    3 +
> > > > > > >  drivers/pci/pci-sysfs.c        |   29 ++++++++++
> > > > > > >  drivers/pci/pci.c              |  110 +++++++++++++++++++++++++++++++++++++----
> > > > > > >  drivers/pci/pci.h              |    1 
> > > > > > >  drivers/pci/pcie/portdrv_pci.c |   44 ++++++++++++++--
> > > > > > >  include/linux/pci.h            |   16 ++++-
> > > > > > >  7 files changed, 205 insertions(+), 21 deletions(-)
> > > > > > > 
> > > > > > > --- a/drivers/pci/pci-acpi.c
> > > > > > > +++ b/drivers/pci/pci-acpi.c
> > > > > > > @@ -48,6 +48,12 @@ static void pci_acpi_wake_dev(acpi_handl
> > > > > > >  	if (event != ACPI_NOTIFY_DEVICE_WAKE || !pci_dev)
> > > > > > >  		return;
> > > > > > >  
> > > > > > > +	if (pci_dev->current_state == PCI_D3cold) {
> > > > > > > +		pci_wakeup_event(pci_dev);
> > > > > > > +		pm_runtime_resume(&pci_dev->dev);
> > > > > > > +		return;
> > > > > > > +	}
> > > > > > > +
> > > > > > >  	if (!pci_dev->pm_cap || !pci_dev->pme_support
> > > > > > >  	     || pci_check_pme_status(pci_dev)) {
> > > > > > >  		if (pci_dev->pme_poll)
> > > > > > > @@ -187,10 +193,13 @@ acpi_status pci_acpi_remove_pm_notifier(
> > > > > > >  
> > > > > > >  static pci_power_t acpi_pci_choose_state(struct pci_dev *pdev)
> > > > > > >  {
> > > > > > > -	int acpi_state;
> > > > > > > +	int acpi_state, d_max;
> > > > > > >  
> > > > > > > -	acpi_state = acpi_pm_device_sleep_state(&pdev->dev, NULL,
> > > > > > > -						ACPI_STATE_D3);
> > > > > 
> > > > > I wonder what tree this patch is against?  The code above doesn't seem to
> > > > > be present in the current mainline.
> > > > 
> > > > As stated in [PATCH -v4 0/2], This patchset is based on:
> > > > 
> > > > [PATCH -v2] ACPI, PM, Specify lowest allowed state for device sleep
> > > > state
> > > > 
> > > > Which is sent to LKML separately.
> > > 
> > > I see.
> > > 
> > > Can you post the latest version of that patch, please?
> > > 
> > > Besides, this hunk of the $subject patch:
> > > 
> > > > @@ -731,8 +791,8 @@ int pci_set_power_state(struct pci_dev *
> > > >       int error;
> > > >  
> > > >       /* bound the state we're entering */
> > > > -     if (state > PCI_D3hot)
> > > > -             state = PCI_D3hot;
> > > > +     if (state > PCI_D3cold)
> > > > +             state = PCI_D3cold;
> > > >       else if (state < PCI_D0)
> > > >               state = PCI_D0;
> > > >       else if ((state == PCI_D1 || state == PCI_D2) && pci_no_d1d2(dev))
> > > > @@ -747,10 +807,15 @@ int pci_set_power_state(struct pci_dev *
> > > >  
> > > >       /* This device is quirked not to be put into D3, so
> > > >          don't put it in D3 */
> > > > -     if (state == PCI_D3hot && (dev->dev_flags & PCI_DEV_FLAGS_NO_D3))
> > > > +     if (state >= PCI_D3hot && (dev->dev_flags & PCI_DEV_FLAGS_NO_D3))
> > > >               return 0;
> > > >  
> > > > -     error = pci_raw_set_power_state(dev, state);
> > > > +     /*
> > > > +      * To put device in D3cold, we put device into D3hot in native
> > > > +      * way, then put device into D3cold with platform ops
> > > > +      */
> > > > +     error = pci_raw_set_power_state(dev, state > PCI_D3hot ?
> > > > +                                     PCI_D3hot : state);
> > > >  
> > > >       if (!__pci_complete_power_transition(dev, state))
> > > >               error = 0;
> > > 
> > > should be merged separately, because it will affect suspend/hibernation code
> > > paths.  Namely, it will change the behavior in such a way that some devices
> > > put into D3hot previously will be put into D3cold now during system suspend.
> > 
> > Yes.  This patch enables both runtime D3cold and D3cold during system
> > suspend.  How about separate this patch into the following patches?
> > 
> > - Add d3cold disable logic, including flags: no_d3cold, d3cold_allowed,
> > runtime_d3cold, and disable runtime d3cold (because part of runtime
> > d3cold support will be enabled by system d3cold support).
> > 
> > - system d3cold support for PCIe port
> > 
> > - system d3cold support in PCI core
> > 
> > - runtime d3cold support for PCIe port
> > 
> > - runtime d3cold support in PCI core
> 
> Sounds good in principle.

Thought it again.

If my understanding were correct, in most cases, The value to put
devices into D3cold during system suspend/hibernate may be questionable.
Because after Linux put the devices into lower power state,  the
firmware may put devices into D3cold state before entering system
suspend state.

So, I think maybe we can just constrain the target state to D3hot in
pci_set_power_state() if system suspend/hibernate is ongoing
(dev->runtime_d3cold is not set).  That is something as follow:

/* D3cold during system suspend/hibernate is not supported yet */
if (dev->runtime_d3cold && state >= PCI_D3cold)
	state = PCI_D3cold;
else if (state > PCI_D3hot)
	state = PCI_D3hot;

This way, we can just make some minor change to this patch and maybe
work on D3cold during system suspend/hibernate after some discussion.

Best Regards,
Huang Ying


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