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commit 3cb4f534bac010258b2688395c2f13459a932be9 upstream. This reverts commitfb097dcd5a. Afterfb097dcd5a("PCI/ASPM: Disable only ASPM_STATE_L1 when driver disables L1"), disabling L1 via pci_disable_link_state(PCIE_LINK_STATE_L1), then enabling one substate, e.g., L1.1, via sysfs actually enables *all* the substates. For example, r8169 disables L1 because of hardware issues on a number of systems, which implicitly disables the L1.1 and L1.2 substates. On some systems, L1 and L1.1 work fine, but L1.2 causes missed rx packets. Enabling L1.1 via the sysfs "aspm_l1_1" attribute unexpectedly enables L1.2 as well as L1.1. Afterfb097dcd5a, pci_disable_link_state(PCIE_LINK_STATE_L1) adds only ASPM_L1 (but not any of the L1.x substates) to the "aspm_disable" mask: --- Beforefb097dcd5a+++ Afterfb097dcd5a# r8169 disables L1: pci_disable_link_state(PCIE_LINK_STATE_L1) - disable |= ASPM_L1 | ASPM_L1_1 | ASPM_L1_2 | ... # disable L1, L1.x + disable |= ASPM_L1 # disable L1 only # write "1" to sysfs "aspm_l1_1" attribute: l1_1_aspm aspm_attr_store_common(state = ASPM_L1_1) disable &= ~ASPM_L1_1 # enable L1.1 if (state & (ASPM_L1_1 | ...)) # if enabling any substate disable &= ~ASPM_L1 # enable L1 # final state: - disable = ASPM_L1_2 | ... # L1, L1.1 enabled; L1.2 disabled + disable = 0 # L1, L1.1, L1.2 all enabled Enabling an L1.x substate removes the substate and L1 from the "aspm_disable" mask. Afterfb097dcd5a, the substates were not added to the mask when disabling L1, so enabling one substate implicitly enables all of them. Revertfb097dcd5aso enabling one substate doesn't enable the others. Link: https://lore.kernel.org/r/c75931ac-7208-4200-9ca1-821629cf5e28@gmail.com Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com> [bhelgaas: work through example in commit log] Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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.