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Subject[PATCH 4.19 089/109] Revert "PCI: PM: Do not read power state in pci_enable_device_flags()"
Date
From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>

[ Upstream commit 4d6035f9bf4ea12776322746a216e856dfe46698 ]

Revert commit 4514d991d992 ("PCI: PM: Do not read power state in
pci_enable_device_flags()") that is reported to cause PCI device
initialization issues on some systems.

BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=213481
Link: https://lore.kernel.org/linux-acpi/YNDoGICcg0V8HhpQ@eldamar.lan
Reported-by: Michael <phyre@rogers.com>
Reported-by: Salvatore Bonaccorso <carnil@debian.org>
Fixes: 4514d991d992 ("PCI: PM: Do not read power state in pci_enable_device_flags()")
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/pci/pci.c | 16 +++++++++++++---
1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 3d59bbe4a5d5..9ebf32de8575 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1585,11 +1585,21 @@ static int pci_enable_device_flags(struct pci_dev *dev, unsigned long flags)
int err;
int i, bars = 0;

- if (atomic_inc_return(&dev->enable_cnt) > 1) {
- pci_update_current_state(dev, dev->current_state);
- return 0; /* already enabled */
+ /*
+ * Power state could be unknown at this point, either due to a fresh
+ * boot or a device removal call. So get the current power state
+ * so that things like MSI message writing will behave as expected
+ * (e.g. if the device really is in D0 at enable time).
+ */
+ if (dev->pm_cap) {
+ u16 pmcsr;
+ pci_read_config_word(dev, dev->pm_cap + PCI_PM_CTRL, &pmcsr);
+ dev->current_state = (pmcsr & PCI_PM_CTRL_STATE_MASK);
}

+ if (atomic_inc_return(&dev->enable_cnt) > 1)
+ return 0; /* already enabled */
+
bridge = pci_upstream_bridge(dev);
if (bridge)
pci_enable_bridge(bridge);
--
2.30.2
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