PCI/PM: Always disable PTM for all devices 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.

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: a697f072f5da ("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>

diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
index 49238ddd39eec54a86873f2859963a80ab9568b9..5d8c37c3e15a2ba395955109ed79557b21c764a2 100644 (file)
--- a/drivers/pci/pci-driver.c
+++ b/drivers/pci/pci-driver.c
@@ -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;

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 83818f81577d666471f4e1aeb8a5b485bcc6f9ee..107afa0a5b03ab08ee83ad625ee70ab59f3b1c6f 100644 (file)
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -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;
 }