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authorRafael J. Wysocki <rjw@rjwysocki.net>2018-03-03 10:53:24 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-05-30 07:47:42 +0200
commitd36edd46526c261b5ce3f7c67ea73d0694f3ff67 (patch)
treea068b7b6390ca5805da2636b8d1448eb261c7b12
parenta1ff9f1524ad547c97372894e27ae6e020c69047 (diff)
PCI: Restore config space on runtime resume despite being unbound
[ Upstream commit 5775b843a619b3c93f946e2b55a208d9f0f48b59 ] We leave PCI devices not bound to a driver in D0 during runtime suspend. But they may have a parent which is bound and can be transitioned to D3cold at runtime. Once the parent goes to D3cold, the unbound child may go to D3cold as well. When the child goes to D3cold, its internal state, including configuration of BARs, MSI, ASPM, MPS, etc., is lost. One example are recent hybrid graphics laptops which cut power to the discrete GPU when the root port above it goes to ACPI power state D3. Users may provoke this by unbinding the GPU driver and allowing runtime PM on the GPU via sysfs: The PM core will then treat the GPU as "suspended", which in turn allows the root port to runtime suspend, causing the power resources listed in its _PR3 object to be powered off. The GPU's BARs will be uninitialized when a driver later probes it. Another example are hybrid graphics laptops where the GPU itself (rather than the root port) is capable of runtime suspending to D3cold. If the GPU's integrated HDA controller is not bound and the GPU's driver decides to runtime suspend to D3cold, the HDA controller's BARs will be uninitialized when a driver later probes it. Fix by saving and restoring config space over a runtime suspend cycle even if the device is not bound. Acked-by: Bjorn Helgaas <bhelgaas@google.com> Tested-by: Peter Wu <peter@lekensteyn.nl> # Nvidia Optimus Tested-by: Lukas Wunner <lukas@wunner.de> # MacBook Pro Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> [lukas: add commit message, bikeshed code comments for clarity] Signed-off-by: Lukas Wunner <lukas@wunner.de> Link: https://patchwork.freedesktop.org/patch/msgid/92fb6e6ae2730915eb733c08e2f76c6a313e3860.1520068884.git.lukas@wunner.de Signed-off-by: Sasha Levin <alexander.levin@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--drivers/pci/pci-driver.c17
1 files changed, 11 insertions, 6 deletions
diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
index 0ad37e69746d..cf4f3ade9233 100644
--- a/drivers/pci/pci-driver.c
+++ b/drivers/pci/pci-driver.c
@@ -1120,11 +1120,14 @@ static int pci_pm_runtime_suspend(struct device *dev)
int error;
/*
- * If pci_dev->driver is not set (unbound), the device should
- * always remain in D0 regardless of the runtime PM status
+ * 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.
+ * Save its config space in case that happens.
*/
- if (!pci_dev->driver)
+ if (!pci_dev->driver) {
+ pci_save_state(pci_dev);
return 0;
+ }
if (!pm || !pm->runtime_suspend)
return -ENOSYS;
@@ -1163,16 +1166,18 @@ static int pci_pm_runtime_resume(struct device *dev)
const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
/*
- * If pci_dev->driver is not set (unbound), the device should
- * always remain in D0 regardless of the runtime PM status
+ * Restoring config space is necessary even if the device is not bound
+ * to a driver because although we left it in D0, it may have gone to
+ * D3cold when the bridge above it runtime suspended.
*/
+ pci_restore_standard_config(pci_dev);
+
if (!pci_dev->driver)
return 0;
if (!pm || !pm->runtime_resume)
return -ENOSYS;
- pci_restore_standard_config(pci_dev);
pci_fixup_device(pci_fixup_resume_early, pci_dev);
__pci_enable_wake(pci_dev, PCI_D0, true, false);
pci_fixup_device(pci_fixup_resume, pci_dev);