Commit 5694ba13 authored Aug 24, 2023 by Feiyang Chen Committed by Bjorn Helgaas Aug 25, 2023

PCI/PM: Only read PCI_PM_CTRL register when available

For a device with no Power Management Capability, pci_power_up() previously
returned 0 (success) if the platform was able to put the device in D0,
which led to pci_set_full_power_state() trying to read PCI_PM_CTRL, even
though it doesn't exist.

Since dev->pm_cap == 0 in this case, pci_set_full_power_state() actually
read the wrong register, interpreted it as PCI_PM_CTRL, and corrupted
dev->current_state. This led to messages like this in some cases:

pci 0000:01:00.0: Refused to change power state from D3hot to D0

To prevent this, make pci_power_up() always return a negative failure code
if the device lacks a Power Management Capability, even if non-PCI platform
power management has been able to put the device in D0. The failure will
prevent pci_set_full_power_state() from trying to access PCI_PM_CTRL.

Fixes: e200904b ("PCI/PM: Split pci_power_up()")
Link: https://lore.kernel.org/r/20230824013738.1894965-1-chenfeiyang@loongson.cn

Signed-off-by: Feiyang Chen <chenfeiyang@loongson.cn>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: stable@vger.kernel.org # v5.19+

parent 06c2afb8

drivers/pci/pci.c

+9 −4

Original line number	Diff line number	Diff line
		@@ -1226,6 +1226,10 @@ static int pci_dev_wait(struct pci_dev dev, char reset_type, int timeout)
		*
		* On success, return 0 or 1, depending on whether or not it is necessary to
		* restore the device's BARs subsequently (1 is returned in that case).
		*
		* On failure, return a negative error code. Always return failure if @dev
		* lacks a Power Management Capability, even if the platform was able to
		* put the device in D0 via non-PCI means.
		*/
		int pci_power_up(struct pci_dev *dev)
		{
		@@ -1242,9 +1246,6 @@ int pci_power_up(struct pci_dev *dev)
		else
		dev->current_state = state;

		if (state == PCI_D0)
		return 0;

		return -EIO;
		}

		@@ -1302,8 +1303,12 @@ static int pci_set_full_power_state(struct pci_dev *dev)
		int ret;

		ret = pci_power_up(dev);
		if (ret < 0)
		if (ret < 0) {
		if (dev->current_state == PCI_D0)
		return 0;

		return ret;
		}

		pci_read_config_word(dev, dev->pm_cap + PCI_PM_CTRL, &pmcsr);
		dev->current_state = pmcsr & PCI_PM_CTRL_STATE_MASK;