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PCI/PM: Always disable PTM for all devices during suspend

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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.

That means we also have to disable PTM on downstream devices.  PCIe r6.0,
sec 2.2.8, recommends that functions support generation of messages in
non-D0 states, so we have to 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).

PTM was previously disabled only for Root Ports, and it was disabled in
pci_prepare_to_sleep(), which is not called at all if a driver supports
legacy PM or does its own state saving.

Instead, disable PTM early in pci_pm_suspend() and pci_pm_runtime_suspend()
so we do it in all cases.

Previously PTM was disabled *after* saving device state, so the state
restore on resume automatically re-enabled it.  Since we now disable PTM
*before* saving state, we must explicitly re-enable it in pci_pm_resume()
and pci_pm_runtime_resume().

Here's a sample of errors that occur when PTM is disabled only on the Root
Port.  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:    [20] UnsupReq               (First)
  pcieport 0000:00:1d.0: AER:   TLP Header: 34000000 08000052 00000000 00000000

Decoding TLP header 0x34...... (0011 0100b) and 0x08000052:

  Fmt                         001b  4 DW header, no data
  Type                     1 0100b  Msg (Local - Terminate at Receiver)
  Requester ID  0x0800              Bus 08 Devfn 00.0
  Message Code    0x52  0101 0010b  PTM Request

The 00:1d.0 Root Port logged an Unsupported Request error when it received
a PTM Request with Requester ID 08:00.0.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=215453
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=216210
Fixes: a697f072f5 ("PCI: Disable PTM during suspend to save power")
Link: https://lore.kernel.org/r/20220909202505.314195-10-helgaas@kernel.org
Reported-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Tested-by: Rajvi Jingar <rajvi.jingar@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
This commit is contained in:
Bjorn Helgaas 2022-09-09 15:25:05 -05:00
parent d736d292bb
commit c01163dbd1
2 changed files with 13 additions and 26 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
drivers/pci/pci-driver.c
View File

@ -774,6 +774,12 @@ static int pci_pm_suspend(struct device *dev)
pci_dev->skip_bus_pm = false;
/*
* Disabling PTM allows some systems, e.g., Intel mobile chips
* since Coffee Lake, to enter a lower-power PM state.
*/
pci_suspend_ptm(pci_dev);
if (pci_has_legacy_pm_support(pci_dev))
return pci_legacy_suspend(dev, PMSG_SUSPEND);
@ -987,6 +993,8 @@ static int pci_pm_resume(struct device *dev)
if (pci_dev->state_saved)
pci_restore_standard_config(pci_dev);
pci_resume_ptm(pci_dev);
if (pci_has_legacy_pm_support(pci_dev))
return pci_legacy_resume(dev);
@ -1274,6 +1282,8 @@ static int pci_pm_runtime_suspend(struct device *dev)
pci_power_t prev = pci_dev->current_state;
int error;
pci_suspend_ptm(pci_dev);
/*
* If pci_dev->driver is not set (unbound), we leave the device in D0,
* but it may go to D3cold when the bridge above it runtime suspends.
@ -1335,6 +1345,7 @@ static int pci_pm_runtime_resume(struct device *dev)
* D3cold when the bridge above it runtime suspended.
*/
pci_pm_default_resume_early(pci_dev);
pci_resume_ptm(pci_dev);
if (!pci_dev->driver)
return 0;

28
drivers/pci/pci.c
View File

@ -2706,24 +2706,12 @@ int pci_prepare_to_sleep(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_suspend_ptm(dev);
pci_enable_wake(dev, target_state, wakeup);
error = pci_set_power_state(dev, target_state);
if (error) {
if (error)
pci_enable_wake(dev, target_state, false);
pci_restore_ptm_state(dev);
}
return error;
}
@ -2764,24 +2752,12 @@ 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_suspend_ptm(dev);
__pci_enable_wake(dev, target_state, pci_dev_run_wake(dev));
error = pci_set_power_state(dev, target_state);
if (error) {
if (error)
pci_enable_wake(dev, target_state, false);
pci_restore_ptm_state(dev);
}
return error;
}