Re: [PATCH v7 0/5] PCI/ASPM: Add sysfs attributes for controlling ASPM

[Bjorn Helgaas <helgaas@kernel.org>]

On Thu, Oct 10, 2019 at 10:45:52PM +0200, Heiner Kallweit wrote:
> On 10.10.2019 15:22, Bjorn Helgaas wrote:
> > On Tue, Oct 08, 2019 at 05:10:40PM -0500, Bjorn Helgaas wrote:
> >> On Sat, Oct 05, 2019 at 02:02:29PM +0200, Heiner Kallweit wrote:
> >>> Background of this extension is a problem with the r8169 network driver.
> >>> Several combinations of board chipsets and network chip versions have
> >>> problems if ASPM is enabled, therefore we have to disable ASPM per
> >>> default. However especially on notebooks ASPM can provide significant
> >>> power-saving, therefore we want to give users the option to enable
> >>> ASPM. With the new sysfs attributes users can control which ASPM
> >>> link-states are disabled.
> >>>
> >>> v2:
> >>> - use a dedicated sysfs attribute per link state
> >>> - allow separate control of ASPM and PCI PM L1 sub-states
> >>>
> >>> v3:
> >>> - patch 3: statically allocate the attribute group
> >>> - patch 3: replace snprintf with printf
> >>> - add patch 4
> >>>
> >>> v4:
> >>> - patch 3: add call to sysfs_update_group because is_visible callback
> >>>            returns false always at file creation time
> >>> - patch 3: simplify code a little
> >>>
> >>> v5:
> >>> - rebased to latest pci/next
> >>>
> >>> v6:
> >>> - patch 3: consider several review comments from Bjorn
> >>> - patch 4: add discussion link to commit message
> >>>
> >>> v7:
> >>> - Move adding pcie_aspm_get_link() to separate patch 3
> >>> - patch 4: change group name from aspm to link_pm
> >>> - patch 4: control visibility of attributes individually
> >>>
> >>> Heiner Kallweit (5):
> >>>   PCI/ASPM: add L1 sub-state support to pci_disable_link_state
> >>>   PCI/ASPM: allow to re-enable Clock PM
> >>>   PCI/ASPM: Add and use helper pcie_aspm_get_link
> >>>   PCI/ASPM: Add sysfs attributes for controlling ASPM link states
> >>>   PCI/ASPM: Remove Kconfig option PCIEASPM_DEBUG and related code
> >>>
> >>>  Documentation/ABI/testing/sysfs-bus-pci |  14 ++
> >>>  drivers/pci/pci-sysfs.c                 |   6 +-
> >>>  drivers/pci/pci.h                       |  12 +-
> >>>  drivers/pci/pcie/Kconfig                |   7 -
> >>>  drivers/pci/pcie/aspm.c                 | 252 ++++++++++++++++--------
> >>>  include/linux/pci.h                     |  10 +-
> >>>  6 files changed, 199 insertions(+), 102 deletions(-)
> >>
> >> I applied these to pci/aspm for v5.5.  Thank you very much for all the
> >> work you put into this!
> >>
> >> There are a couple questions that are still open, but I have no
> >> problem if we want to make minor tweaks before the merge window opens.
> > 
> > To resolve these open questions, I propose the diff below, which:
> > 
> >   - Makes pcie_aspm_get_link() work only when called for an Upstream
> >     Port (Endpoint, Switch Upstream Port, or other component at the
> >     downstream end of a Link).  I don't think there's any caller that
> >     needs to supply the upstream end.
> > 
> >   - Makes pcie_aspm_get_link() check that both ends are PCIe devices.
> >     This might be overkill, but we can't rely on the PCI topology
> >     being "correct", e.g., we have to deal gracefully with a
> >     virtualization or similar scenario where a bridge is PCI and the
> >     child is PCIe.  In that case, we shouldn't try to manage ASPM, so
> >     we don't need a link_state, but I couldn't quite convince myself
> >     that pcie_aspm_init_link_state() handles these cases.
> > 
> >   - Removes the aspm_lock from the sysfs show functions.  Per the
> >     discussion with Rafael, I don't think it's necessary there:
> > 
> >       https://lore.kernel.org/r/20191007223428.GA72605@google.com
> > 
> >     I didn't remove it from the store functions because they do ASPM
> >     reconfiguration and I didn't try to figure out the locking there.
> > 
> > Let me know what you think about this.  If it looks right, I'll just
> > squash these changes into the relevant patches.
> > 
> Looks good to me. Thanks, Heiner

Thanks, I squashed these in and updated pci/aspm.