mainlining shenanigans
0b59193548
Notice that calling pci_update_current_state() from pci_power_up() is redundant and may be harmful in some cases. First, if the device is in a low-power state before pci_power_up() gets called for it and platform_pci_set_power_state() successfully changes its power state to D0, pci_update_current_state() will update current_state to reflect that and pci_power_up() will return success right away without restoring the device's BARs or reconfiguring ASPM which may be necessary. This is arguably incorrect and definitely inconsistent with the case when platform_pci_set_power_state() returns an error (for example, because the device is not power-manageable by the platform firmware). Second, current_state should not be overwritten until the decision whether or not to restore the device's BARs is made, because that decision generally depends on its value. Again, calling pci_update_current_state() in pci_power_up() is not consistent with this observation. Next, pci_power_up() attempts to read from the device's PCI_PM_CTRL register regardless of the current_state value unless it is PCI_D0, including the case when pci_update_current_state() sets current_state to PCI_D3cold to indicate that the device is not accessible. If the register read is not successful, current_state will be set to PCI_D3cold anyway, so that pci_update_current_state() action is redundant. Further, if pci_update_current_state() reads the device's PCI_PM_CTRL register, pci_power_up() will repeat that read going forward and it is not necessary to update current_state in the meantime. Finally, if pm_cap is not set (in which case the PCI_PM_CTRL register is not present), the power state of the device should be determined with the help of the platform firmware or set to D0 if that's not possible and pci_update_current_state() does not do that. Accordingly, rearrange pci_power_up() so as to address the above shortcomings. Link: https://lore.kernel.org/r/3695055.kQq0lBPeGt@kreacher Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> |
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| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
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.