On 8/30/22 8:52 AM, Bjorn Helgaas wrote: > From: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> > > During suspend, we want to disable PTM on Root Ports because that allows > some chips, e.g., Intel mobile chips since Coffee Lake, to enter a > lower-power PM state. > > Previously we only disabled PTM for Root Ports, but PCIe r6.0, sec 2.2.8, > strongly recommends that functions support generation of Messages in non-D0 > states, so we must assume that Switch Upstream Ports or Endpoints may send > PTM Request Messages while in D1, D2, and D3hot. > > A PTM Message received by a Downstream Port, e.g., a Root Port, with PTM > disabled must be treated as an Unsupported Request (sec 6.21.3). > > With this topology: > > 0000:00:1d.0 Root Port to [bus 08-71] > 0000:08:00.0 Switch Upstream Port to [bus 09-71] > > Kai-Heng reported errors like this: > > pcieport 0000:00:1d.0: AER: Uncorrected (Non-Fatal) error received: 0000:00:1d.0 > pcieport 0000:00:1d.0: PCIe Bus Error: severity=Uncorrected (Non-Fatal), type=Transaction Layer, (Requester ID) > pcieport 0000:00:1d.0: device [8086:7ab0] error status/mask=00100000/00004000 > pcieport 0000:00:1d.0: [20] UnsupReq (First) > pcieport 0000:00:1d.0: AER: TLP Header: 34000000 08000052 00000000 00000000 > > Decoding this (from PCIe r6.0, sec 2.2.1.1, 2.2.8.10) shows that 00:1d.0 > logged an Unsupported Request error when it received a PTM Request with > Requester ID 08:00.0. > > To prevent this error, disable PTM when suspending Upstream Ports > (including those on Endpoints), not just Root Ports. > > Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=215453 > Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=216210 > Based-on: https://lore.kernel.org/r/20220706123244.18056-1-kai.heng.feng@xxxxxxxxxxxxx > Based-on-patch-by: Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx> > Reported-by: Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx> > Tested-by: Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx> > Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> > Cc: David E. Box <david.e.box@xxxxxxxxxxxxxxx> > Cc: Sathyanarayanan Kuppuswamy <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx> > --- Looks good to me Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx> > drivers/pci/pci.c | 30 ++++++++++++++---------------- > drivers/pci/pcie/ptm.c | 8 +++++++- > 2 files changed, 21 insertions(+), 17 deletions(-) > > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c > index 95bc329e74c0..96487a9ce5bf 100644 > --- a/drivers/pci/pci.c > +++ b/drivers/pci/pci.c > @@ -2707,14 +2707,19 @@ int pci_prepare_to_sleep(struct pci_dev *dev) > return -EIO; > > /* > - * 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. > + * We want to disable PTM on Root Ports because that allows some > + * chips, e.g., Intel mobile chips since Coffee Lake, to enter a > + * lower-power PM state. > + * > + * PCIe r6.0, sec 2.2.8, strongly recommends that functions support > + * generation of messages in non-D0 states, so we assume Switch > + * Upstream Ports or Endpoints may send PTM Requests while in D1, > + * D2, and D3hot. A PTM message received by a Downstream Port > + * (including a Root Port) with PTM disabled must be treated as an > + * Unsupported Request (sec 6.21.3). To prevent this error, > + * disable PTM in *all* devices, not just Root Ports. > */ > - if (pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT) > - pci_disable_ptm(dev); > + pci_disable_ptm(dev); > > pci_enable_wake(dev, target_state, wakeup); > > @@ -2764,15 +2769,8 @@ int pci_finish_runtime_suspend(struct pci_dev *dev) > if (target_state == PCI_POWER_ERROR) > return -EIO; > > - /* > - * 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(dev) == PCI_EXP_TYPE_ROOT_PORT) > - pci_disable_ptm(dev); > + /* See rationale above for disabling PTM */ > + pci_disable_ptm(dev); > > __pci_enable_wake(dev, target_state, pci_dev_run_wake(dev)); > > diff --git a/drivers/pci/pcie/ptm.c b/drivers/pci/pcie/ptm.c > index 368a254e3124..ec338470d13f 100644 > --- a/drivers/pci/pcie/ptm.c > +++ b/drivers/pci/pcie/ptm.c > @@ -31,12 +31,18 @@ static void pci_ptm_info(struct pci_dev *dev) > > void pci_disable_ptm(struct pci_dev *dev) > { > - int ptm; > + int type, ptm; > u16 ctrl; > > if (!pci_is_pcie(dev)) > return; > > + type = pci_pcie_type(dev); > + if (!(type == PCI_EXP_TYPE_ROOT_PORT || > + type == PCI_EXP_TYPE_UPSTREAM || > + type == PCI_EXP_TYPE_ENDPOINT)) > + return; > + > ptm = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_PTM); > if (!ptm) > return; -- Sathyanarayanan Kuppuswamy Linux Kernel Developer
