[PATCH] PCI/ASPM: Remove pcie_aspm_pm_state_change()

[PATCH] PCI/ASPM: Remove pcie_aspm_pm_state_change()

[Mark Hasemeyer]

From: Kai-Heng Feng <kai.heng.feng@canonical.com>

commit 08d0cc5f34265d1a1e3031f319f594bd1970976c upstream.

pcie_aspm_pm_state_change() was introduced at the inception of PCIe ASPM
code, but it can cause some issues. For instance, when ASPM config is
changed via sysfs, those changes won't persist across power state change
because pcie_aspm_pm_state_change() overwrites them.

Also, if the driver restores L1SS [1] after system resume, the restored
state will also be overwritten by pcie_aspm_pm_state_change().

Remove pcie_aspm_pm_state_change().  If there's any hardware that really
needs it to function, a quirk can be used instead.

[1] https://lore.kernel.org/linux-pci/20220201123536.12962-1-vidyas@nvidia.com/
Link: https://lore.kernel.org/r/20220509073639.2048236-1-kai.heng.feng@canonical.com
[bhelgaas: remove additional pcie_aspm_pm_state_change() call in
pci_set_low_power_state(), added by
10aa5377fc8a ("PCI/PM: Split pci_raw_set_power_state()") and moved by
7957d201456f ("PCI/PM: Relocate pci_set_low_power_state()")]
Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
[manual backport: pci_set_low_power_state does not exist in v5.15]
Signed-off-by: Mark Hasemeyer <markhas@chromium.org>
---
This change is intended for, and has been tested against 5.15.y.
It is desired because without it, it has been observed that re-applying
aspm settings can cause the system to crash with certain pci devices
(ie.  Genesys GL9755).

A manual backport was required as `pci_set_low_power_state` does not exist in
v5.15.

Tested by issuing 100 suspend/resume cycles on a symptomatic system running
5.15.107.

Test command:
```
echo +5 > /sys/class/rtc/rtc0/wakealarm && echo freeze > /sys/power/state

```

L1 settings looked identical before and after:
```
localhost ~ # lspci -vvv -d 0x17a0: | grep L1Sub
                L1SubCap: PCI-PM_L1.2+ PCI-PM_L1.1+ ASPM_L1.2+ ASPM_L1.1+ L1_PM_Substates+
                L1SubCtl1: PCI-PM_L1.2- PCI-PM_L1.1+ ASPM_L1.2- ASPM_L1.1+
                L1SubCtl2: T_PwrOn=3100us
```

 drivers/pci/pci.c       |  3 ---
 drivers/pci/pci.h       |  2 --
 drivers/pci/pcie/aspm.c | 19 -------------------
 3 files changed, 24 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 649df298869c..4aa2e655398c 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1140,9 +1140,6 @@ static int pci_raw_set_power_state(struct pci_dev *dev, pci_power_t state)
 	if (need_restore)
 		pci_restore_bars(dev);
 
-	if (dev->bus->self)
-		pcie_aspm_pm_state_change(dev->bus->self);
-
 	return 0;
 }
 
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 72280e9b23b2..e6ea6e950428 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -595,12 +595,10 @@ bool pcie_wait_for_link(struct pci_dev *pdev, bool active);
 #ifdef CONFIG_PCIEASPM
 void pcie_aspm_init_link_state(struct pci_dev *pdev);
 void pcie_aspm_exit_link_state(struct pci_dev *pdev);
-void pcie_aspm_pm_state_change(struct pci_dev *pdev);
 void pcie_aspm_powersave_config_link(struct pci_dev *pdev);
 #else
 static inline void pcie_aspm_init_link_state(struct pci_dev *pdev) { }
 static inline void pcie_aspm_exit_link_state(struct pci_dev *pdev) { }
-static inline void pcie_aspm_pm_state_change(struct pci_dev *pdev) { }
 static inline void pcie_aspm_powersave_config_link(struct pci_dev *pdev) { }
 #endif
 
diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index 013a47f587ce..b3ad316418f1 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -1020,25 +1020,6 @@ void pcie_aspm_exit_link_state(struct pci_dev *pdev)
 	up_read(&pci_bus_sem);
 }
 
-/* @pdev: the root port or switch downstream port */
-void pcie_aspm_pm_state_change(struct pci_dev *pdev)
-{
-	struct pcie_link_state *link = pdev->link_state;
-
-	if (aspm_disabled || !link)
-		return;
-	/*
-	 * Devices changed PM state, we should recheck if latency
-	 * meets all functions' requirement
-	 */
-	down_read(&pci_bus_sem);
-	mutex_lock(&aspm_lock);
-	pcie_update_aspm_capable(link->root);
-	pcie_config_aspm_path(link);
-	mutex_unlock(&aspm_lock);
-	up_read(&pci_bus_sem);
-}
-
 void pcie_aspm_powersave_config_link(struct pci_dev *pdev)
 {
 	struct pcie_link_state *link = pdev->link_state;
-- 
2.40.0.634.g4ca3ef3211-goog