mirror of
https://github.com/rd-stuffs/msm-4.14.git
synced 2025-02-20 11:45:48 +08:00
5e1edd01d5
[ Upstream commit 4514d991d99211f225d83b7e640285f29f0755d0 ]
It should not be necessary to update the current_state field of
struct pci_dev in pci_enable_device_flags() before calling
do_pci_enable_device() for the device, because none of the
code between that point and the pci_set_power_state() call in
do_pci_enable_device() invoked later depends on it.
Moreover, doing that is actively harmful in some cases. For example,
if the given PCI device depends on an ACPI power resource whose _STA
method initially returns 0 ("off"), but the config space of the PCI
device is accessible and the power state retrieved from the
PCI_PM_CTRL register is D0, the current_state field in the struct
pci_dev representing that device will get out of sync with the
power.state of its ACPI companion object and that will lead to
power management issues going forward.
To avoid such issues it is better to leave the current_state value
as is until it is changed to PCI_D0 by do_pci_enable_device() as
appropriate. However, the power state of the device is not changed
to PCI_D0 if it is already enabled when pci_enable_device_flags()
gets called for it, so update its current_state in that case, but
use pci_update_current_state() covering platform PM too for that.
Link: https://lore.kernel.org/lkml/20210314000439.3138941-1-luzmaximilian@gmail.com/
Reported-by: Maximilian Luz <luzmaximilian@gmail.com>
Tested-by: Maximilian Luz <luzmaximilian@gmail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.