> -----Original Message----- > From: Bjorn Helgaas <helgaas@xxxxxxxxxx> > Sent: Friday, April 22, 2022 3:25 PM > To: Jingar, Rajvi <rajvi.jingar@xxxxxxxxx> > Cc: bhelgaas@xxxxxxxxxx; david.e.box@xxxxxxxxxxxxxxx; linux- > pci@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; linux-pm@xxxxxxxxxxxxxxx; > Wysocki, Rafael J <rafael.j.wysocki@xxxxxxxxx>; Kai-Heng Feng > <kai.heng.feng@xxxxxxxxxxxxx>; mika.westerberg@xxxxxxxxxxxxxxx; > koba.ko@xxxxxxxxxxxxx; baolu.lu@xxxxxxxxxxxxxxx; > sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx; Russell Currey > <ruscur@xxxxxxxxxx>; Oliver O'Halloran <oohall@xxxxxxxxx>; linuxppc- > dev@xxxxxxxxxxxxxxxx > Subject: Re: [PATCH v4 2/2] PCI/PM: Fix pci_pm_suspend_noirq() to disable PTM > > [+cc other folks interested in PTM from > https://lore.kernel.org/r/20220408153159.106741-1- > kai.heng.feng@xxxxxxxxxxxxx] > > On Thu, Apr 14, 2022 at 07:54:02PM +0200, Rafael J. Wysocki wrote: > > On 3/25/2022 8:50 PM, Rajvi Jingar wrote: > > > For the PCIe devices (like nvme) that do not go into D3 state still need to > > > disable PTM on PCIe root ports to allow the port to enter a lower-power PM > > > state and the SoC to reach a lower-power idle state as a whole. Move the > > > pci_disable_ptm() out of pci_prepare_to_sleep() as this code path is not > > > followed for devices that do not go into D3. This patch fixes the issue > > > seen on Dell XPS 9300 with Ice Lake CPU and Dell Precision 5530 with Coffee > > > Lake CPU platforms to get improved residency in low power idle states. > > > > > > Fixes: a697f072f5da ("PCI: Disable PTM during suspend to save power") > > > Signed-off-by: Rajvi Jingar <rajvi.jingar@xxxxxxxxx> > > > Suggested-by: David E. Box <david.e.box@xxxxxxxxxxxxxxx> > > > > --- > > > v1 -> v2: add Fixes tag in commit message > > > v2 -> v3: move changelog after "---" marker > > > v3 -> v4: add "---" marker after changelog > > > --- > > > drivers/pci/pci-driver.c | 10 ++++++++++ > > > drivers/pci/pci.c | 10 ---------- > > > 2 files changed, 10 insertions(+), 10 deletions(-) > > > > > > diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c > > > index 8b55a90126a2..ab733374a260 100644 > > > --- a/drivers/pci/pci-driver.c > > > +++ b/drivers/pci/pci-driver.c > > > @@ -847,6 +847,16 @@ static int pci_pm_suspend_noirq(struct device *dev) > > > if (!pci_dev->state_saved) { > > > pci_save_state(pci_dev); > > > + /* > > > + * There are systems (for example, Intel mobile chips since > Coffee > > > + * Lake) where the power drawn while suspended can be > significantly > > > + * reduced by disabling PTM on PCIe root ports as this allows the > > > + * port to enter a lower-power PM state and the SoC to reach a > > > + * lower-power idle state as a whole. > > > + */ > > > + if (pci_pcie_type(pci_dev) == PCI_EXP_TYPE_ROOT_PORT) > > > + pci_disable_ptm(pci_dev); > > Why is disabling PTM dependent on pci_dev->state_saved? The point of > this is to change the behavior of the device, and it seems like we > want to do that regardless of whether the driver has used > pci_save_state(). > Because we use the saved state to restore PTM on the root port. And it's under this condition that the root port state gets saved. > Bjorn
