[J] [PATCH 09/10] PCI/PM: Always disable PTM for all devices during suspend

[Kai-Heng Feng]

From: Bjorn Helgaas <bhelgaas at google.com>

BugLink: https://bugs.launchpad.net/bugs/1988797

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 at canonical.com>
Tested-by: Rajvi Jingar <rajvi.jingar at linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas at google.com>
Reviewed-by: Mika Westerberg <mika.westerberg at linux.intel.com>
(backported from commit c01163dbd1b8aa016c163ff4bf3a2e90311504f1 linux-next)
[khfeng: resolve conflict caused by refactoring ]
Signed-off-by: Kai-Heng Feng <kai.heng.feng at canonical.com>
---
 drivers/pci/pci-driver.c | 11 +++++++++++
 drivers/pci/pci.c        | 25 +------------------------
 2 files changed, 12 insertions(+), 24 deletions(-)

diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
index 2761ab86490d1..d3e99c8ff28bb 100644
--- a/drivers/pci/pci-driver.c
+++ b/drivers/pci/pci-driver.c
@@ -743,6 +743,12 @@ 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);
 
@@ -956,6 +962,8 @@ 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);
 
@@ -1243,6 +1251,8 @@ 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.
@@ -1304,6 +1314,7 @@ static int pci_pm_runtime_resume(struct device *dev)
 	 * D3cold when the bridge above it runtime suspended.
 	 */
 	pci_restore_standard_config(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 d447074886305..5d06f7dcac735 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -2695,24 +2695,12 @@ 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;
 }
@@ -2750,23 +2738,12 @@ int pci_finish_runtime_suspend(struct pci_dev *dev)
 
 	dev->runtime_d3cold = target_state == PCI_D3cold;
 
-	/*
-	 * 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) {
 		pci_enable_wake(dev, target_state, false);
-		pci_restore_ptm_state(dev);
 		dev->runtime_d3cold = false;
 	}
 
-- 
2.34.1