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> --- 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; -- 2.25.1
