Re: [PATCH V1] PCI/ASPM: Update saved buffers with latest ASPM configuration

[Vidya Sagar]

On 1/25/2023 8:31 PM, Wysocki, Rafael J wrote:
> External email: Use caution opening links or attachments
>
>
> On 1/25/2023 2:38 PM, Vidya Sagar wrote:
> > Many PCIe device drivers save the configuration state of their respective
> > devices during probe and restore the same when their 'slot_reset' hook
> > is called through PCIe Error Recovery System.
> > If the system has a change in ASPM policy after the driver's probe is
> > called and before error event occurred, 'slot_reset' hook restores the
> > PCIe configuration state to what it was at the time of probe but not with
> > what it was just before the occurrence of the error event.
> > This effectively leads to a mismatch in the ASPM configuration between
> > the device and its upstream parent device.
> > This patch addresses that issue by updating the saved configuration state
> > of the device with the latest info whenever there is a change w.r.t ASPM
> > policy.
> >
> > Signed-off-by: Vidya Sagar <vidyas@xxxxxxxxxx>
>
> If it is a bug fix (which I think it is), a Fixes tag should be present
> here.

It is kind of a bug fix but I couldn't pin point to any particular 
commit that would have introduced it.

> If the reporter's names are known, Reported-by tags should be present
> here too.

I was experimenting with the error handling code and happen to find this.

> If anyone except for you has tested this patch, a Tested-by tag should
> be present here.

Only I tested this patch for now. It would be great if more verification 
is done on this patch.

Thanks,
Vidya Sagar

> > ---
> >   drivers/pci/pci.h       |  4 ++++
> >   drivers/pci/pcie/aspm.c | 40 ++++++++++++++++++++++++++++++++++++++++
> >   2 files changed, 44 insertions(+)
> >
> > diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> > index 9ed3b5550043..f4a91d4fe96d 100644
> > --- a/drivers/pci/pci.h
> > +++ b/drivers/pci/pci.h
> > @@ -566,12 +566,16 @@ bool pcie_wait_for_link(struct pci_dev *pdev, 
> > bool active);
> >   void pcie_aspm_init_link_state(struct pci_dev *pdev);
> >   void pcie_aspm_exit_link_state(struct pci_dev *pdev);
> >   void pcie_aspm_powersave_config_link(struct pci_dev *pdev);
> > +void pci_save_aspm_state(struct pci_dev *dev);
> > +void pci_restore_aspm_state(struct pci_dev *dev);
> >   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_powersave_config_link(struct pci_dev 
> > *pdev) { }
> > +static inline void pci_save_aspm_state(struct pci_dev *dev) { }
> > +static inline void pci_restore_aspm_state(struct pci_dev *dev) { }
> >   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
> > diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
> > index 53a1fa306e1e..f25e0440d36b 100644
> > --- a/drivers/pci/pcie/aspm.c
> > +++ b/drivers/pci/pcie/aspm.c
> > @@ -151,6 +151,7 @@ static void pcie_set_clkpm_nocheck(struct 
> > pcie_link_state *link, int enable)
> >                                                  
> > PCI_EXP_LNKCTL_CLKREQ_EN,
> >                                                  val);
> >       link->clkpm_enabled = !!enable;
> > +     pci_save_aspm_state(child);
> >   }
> >
> >   static void pcie_set_clkpm(struct pcie_link_state *link, int enable)
> > @@ -757,6 +758,39 @@ static void pcie_config_aspm_l1ss(struct 
> > pcie_link_state *link, u32 state)
> >                               PCI_L1SS_CTL1_L1SS_MASK, val);
> >   }
> >
> > +void pci_save_aspm_state(struct pci_dev *dev)
> > +{
> > +     int i = 0;
> > +     struct pci_cap_saved_state *save_state;
> > +     u16 *cap;
> > +
> > +     if (!pci_is_pcie(dev))
> > +             return;
> > +
> > +     save_state = pci_find_saved_cap(dev, PCI_CAP_ID_EXP);
> > +     if (!save_state)
> > +             return;
> > +
> > +     cap = (u16 *)&save_state->cap.data[0];
> > +     i++;
> > +     pcie_capability_read_word(dev, PCI_EXP_LNKCTL, &cap[i++]);
> > +}
> > +
> > +void pci_restore_aspm_state(struct pci_dev *dev)
> > +{
> > +     int i = 0;
> > +     struct pci_cap_saved_state *save_state;
> > +     u16 *cap;
> > +
> > +     save_state = pci_find_saved_cap(dev, PCI_CAP_ID_EXP);
> > +     if (!save_state)
> > +             return;
> > +
> > +     cap = (u16 *)&save_state->cap.data[0];
> > +     i++;
> > +     pcie_capability_write_word(dev, PCI_EXP_LNKCTL, cap[i++]);
> > +}
> > +
> >   void pci_save_aspm_l1ss_state(struct pci_dev *dev)
> >   {
> >       struct pci_cap_saved_state *save_state;
> > @@ -849,6 +883,12 @@ static void pcie_config_aspm_link(struct 
> > pcie_link_state *link, u32 state)
> >               pcie_config_aspm_dev(parent, upstream);
> >
> >       link->aspm_enabled = state;
> > +
> > +     /* Update latest ASPM configuration in saved context */
> > +     pci_save_aspm_state(link->downstream);
> > +     pci_save_aspm_l1ss_state(link->downstream);
> > +     pci_save_aspm_state(parent);
> > +     pci_save_aspm_l1ss_state(parent);
> >   }
> >
> >   static void pcie_config_aspm_path(struct pcie_link_state *link)