Re: [PATCH V2] PCI/ASPM: Save/restore L1SS Capability for suspend/resume

[Bjorn Helgaas <helgaas@kernel.org>]

[+cc Kai-Heng]

On Wed, Jul 13, 2022 at 11:29:42PM +0530, Vidya Sagar wrote:
> Hi,
> @Kenneth, Could you please verify it on your laptop one last time?
> 
> @Bjorn, Could you please review this change in the meanwhile?

Seems like this may be related to Kai-Heng's patch:
https://lore.kernel.org/r/20220509073639.2048236-1-kai.heng.feng@canonical.com
since he specifically mentioned L1SS.

I applied Kai-Heng's patch for v5.20 yesterday, but I haven't worked
out the connection to this patch.  But if you want Kenneth to test
this, it should probably be on top of Kai-Heng's patch so we're
testing something close to the eventual result.

> On 7/5/2022 11:30 AM, Vidya Sagar wrote:
> > External email: Use caution opening links or attachments
> > 
> > 
> > Previously ASPM L1 Substates control registers (CTL1 and CTL2) weren't
> > saved and restored during suspend/resume leading to L1 Substates
> > configuration being lost post-resume.
> > 
> > Save the L1 Substates control registers so that the configuration is
> > retained post-resume.
> > 
> > Signed-off-by: Vidya Sagar <vidyas@nvidia.com>
> > Tested-by: Abhishek Sahu <abhsahu@nvidia.com>
> > ---
> > Hi,
> > Kenneth R. Crudup <kenny@panix.com>, Could you please verify this patch
> > on your laptop (Dell XPS 13) one last time?
> > IMHO, the regression observed on your laptop with an old version of the patch
> > could be due to a buggy old version BIOS in the laptop.
> > 
> > Thanks,
> > Vidya Sagar
> > 
> >   drivers/pci/pci.c       |  7 +++++++
> >   drivers/pci/pci.h       |  4 ++++
> >   drivers/pci/pcie/aspm.c | 44 +++++++++++++++++++++++++++++++++++++++++
> >   3 files changed, 55 insertions(+)
> > 
> > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> > index cfaf40a540a8..aca05880aaa3 100644
> > --- a/drivers/pci/pci.c
> > +++ b/drivers/pci/pci.c
> > @@ -1667,6 +1667,7 @@ int pci_save_state(struct pci_dev *dev)
> >                  return i;
> > 
> >          pci_save_ltr_state(dev);
> > +       pci_save_aspm_l1ss_state(dev);
> >          pci_save_dpc_state(dev);
> >          pci_save_aer_state(dev);
> >          pci_save_ptm_state(dev);
> > @@ -1773,6 +1774,7 @@ void pci_restore_state(struct pci_dev *dev)
> >           * LTR itself (in the PCIe capability).
> >           */
> >          pci_restore_ltr_state(dev);
> > +       pci_restore_aspm_l1ss_state(dev);
> > 
> >          pci_restore_pcie_state(dev);
> >          pci_restore_pasid_state(dev);
> > @@ -3489,6 +3491,11 @@ void pci_allocate_cap_save_buffers(struct pci_dev *dev)
> >          if (error)
> >                  pci_err(dev, "unable to allocate suspend buffer for LTR\n");
> > 
> > +       error = pci_add_ext_cap_save_buffer(dev, PCI_EXT_CAP_ID_L1SS,
> > +                                           2 * sizeof(u32));
> > +       if (error)
> > +               pci_err(dev, "unable to allocate suspend buffer for ASPM-L1SS\n");
> > +
> >          pci_allocate_vc_save_buffers(dev);
> >   }
> > 
> > diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> > index e10cdec6c56e..92d8c92662a4 100644
> > --- a/drivers/pci/pci.h
> > +++ b/drivers/pci/pci.h
> > @@ -562,11 +562,15 @@ void pcie_aspm_init_link_state(struct pci_dev *pdev);
> >   void pcie_aspm_exit_link_state(struct pci_dev *pdev);
> >   void pcie_aspm_pm_state_change(struct pci_dev *pdev);
> >   void pcie_aspm_powersave_config_link(struct pci_dev *pdev);
> > +void pci_save_aspm_l1ss_state(struct pci_dev *dev);
> > +void pci_restore_aspm_l1ss_state(struct pci_dev *dev);
> >   #else
> >   static inline void pcie_aspm_init_link_state(struct pci_dev *pdev) { }
> >   static inline void pcie_aspm_exit_link_state(struct pci_dev *pdev) { }
> >   static inline void pcie_aspm_pm_state_change(struct pci_dev *pdev) { }
> >   static inline void pcie_aspm_powersave_config_link(struct pci_dev *pdev) { }
> > +static inline void pci_save_aspm_l1ss_state(struct pci_dev *dev) { }
> > +static inline void pci_restore_aspm_l1ss_state(struct pci_dev *dev) { }
> >   #endif
> > 
> >   #ifdef CONFIG_PCIE_ECRC
> > diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
> > index a96b7424c9bc..2c29fdd20059 100644
> > --- a/drivers/pci/pcie/aspm.c
> > +++ b/drivers/pci/pcie/aspm.c
> > @@ -726,6 +726,50 @@ static void pcie_config_aspm_l1ss(struct pcie_link_state *link, u32 state)
> >                                  PCI_L1SS_CTL1_L1SS_MASK, val);
> >   }
> > 
> > +void pci_save_aspm_l1ss_state(struct pci_dev *dev)
> > +{
> > +       int aspm_l1ss;
> > +       struct pci_cap_saved_state *save_state;
> > +       u32 *cap;
> > +
> > +       if (!pci_is_pcie(dev))
> > +               return;
> > +
> > +       aspm_l1ss = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_L1SS);
> > +       if (!aspm_l1ss)
> > +               return;
> > +
> > +       save_state = pci_find_saved_ext_cap(dev, PCI_EXT_CAP_ID_L1SS);
> > +       if (!save_state)
> > +               return;
> > +
> > +       cap = (u32 *)&save_state->cap.data[0];
> > +       pci_read_config_dword(dev, aspm_l1ss + PCI_L1SS_CTL2, cap++);
> > +       pci_read_config_dword(dev, aspm_l1ss + PCI_L1SS_CTL1, cap++);
> > +}
> > +
> > +void pci_restore_aspm_l1ss_state(struct pci_dev *dev)
> > +{
> > +       int aspm_l1ss;
> > +       struct pci_cap_saved_state *save_state;
> > +       u32 *cap;
> > +
> > +       if (!pci_is_pcie(dev))
> > +               return;
> > +
> > +       aspm_l1ss = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_L1SS);
> > +       if (!aspm_l1ss)
> > +               return;
> > +
> > +       save_state = pci_find_saved_ext_cap(dev, PCI_EXT_CAP_ID_L1SS);
> > +       if (!save_state)
> > +               return;
> > +
> > +       cap = (u32 *)&save_state->cap.data[0];
> > +       pci_write_config_dword(dev, aspm_l1ss + PCI_L1SS_CTL2, *cap++);
> > +       pci_write_config_dword(dev, aspm_l1ss + PCI_L1SS_CTL1, *cap++);
> > +}
> > +
> >   static void pcie_config_aspm_dev(struct pci_dev *pdev, u32 val)
> >   {
> >          pcie_capability_clear_and_set_word(pdev, PCI_EXP_LNKCTL,
> > --
> > 2.17.1
> >