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Code Issues Releases Packages Activity

Revert "PCI/ASPM: Save L1 PM Substates Capability for suspend/resume"

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This reverts commit 4ff116d0d5.

Tasev Nikola and Mark Enriquez reported that resume from suspend was broken
in v6.1-rc1.  Tasev bisected to a47126ec29 ("PCI/PTM: Cache PTM
Capability offset"), but we can't figure out how that could be related.

Mark saw the same symptoms and bisected to 4ff116d0d5 ("PCI/ASPM: Save L1
PM Substates Capability for suspend/resume"), which does have a connection:
it restores L1 Substates configuration while ASPM L1 may be enabled:

  pci_restore_state
    pci_restore_aspm_l1ss_state
      aspm_program_l1ss
        pci_write_config_dword(PCI_L1SS_CTL1, ctl1)         # L1SS restore
    pci_restore_pcie_state
      pcie_capability_write_word(PCI_EXP_LNKCTL, cap[i++])  # L1 restore

which is a problem because PCIe r6.0, sec 5.5.4, requires that:

  If setting either or both of the enable bits for ASPM L1 PM
  Substates, both ports must be configured as described in this
  section while ASPM L1 is disabled.

Separately, Thomas Witt reported that 5e85eba6f5 ("PCI/ASPM: Refactor L1
PM Substates Control Register programming") broke suspend/resume, and it
depends on 4ff116d0d5.

Revert 4ff116d0d5 ("PCI/ASPM: Save L1 PM Substates Capability for
suspend/resume") to fix the resume issue and enable revert of 5e85eba6f5
to fix the issue Thomas reported.

Note that reverting 4ff116d0d5 means L1 Substates config may be lost on
suspend/resume.  As far as we know the system will use more power but will
still *work* correctly.

Fixes: 4ff116d0d5 ("PCI/ASPM: Save L1 PM Substates Capability for suspend/resume")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=216782
Link: https://bugzilla.kernel.org/show_bug.cgi?id=216877
Reported-by: Tasev Nikola <tasev.stefanoska@skynet.be>
Reported-by: Mark Enriquez <enriquezmark36@gmail.com>
Reported-by: Thomas Witt <kernel@witt.link>
Tested-by: Mark Enriquez <enriquezmark36@gmail.com>
Tested-by: Thomas Witt <kernel@witt.link>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: stable@vger.kernel.org	# v6.1+
Cc: Vidya Sagar <vidyas@nvidia.com>
This commit is contained in:
Bjorn Helgaas 2023-02-03 13:57:29 -06:00
commit a7152be79b
3 changed files with 0 additions and 48 deletions
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