Great. Thanks Vidya. On Wed, 2020-12-09 at 09:38 +0530, Vidya Sagar wrote: > There is a change already available for it in linux-next > https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?id=4257f7e008ea394fcecc050f1569c3503b8bcc15 > > Thanks, > Vidya Sagar > > On 12/9/2020 3:36 AM, David E. Box wrote: > > External email: Use caution opening links or attachments > > > > > > On Intel systems that support ACPI Low Power Idle it has been > > observed > > that the L1 Substate capability can return disabled after a s2idle > > cycle. This causes the loss of L1 Substate support during runtime > > leading to higher power consumption. Add save/restore of the L1SS > > control registers. > > > > Signed-off-by: David E. Box <david.e.box@xxxxxxxxxxxxxxx> > > --- > > drivers/pci/pci.c | 49 > > +++++++++++++++++++++++++++++++++++++++++++++++ > > 1 file changed, 49 insertions(+) > > > > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c > > index e578d34095e9..beee3d9952a6 100644 > > --- a/drivers/pci/pci.c > > +++ b/drivers/pci/pci.c > > @@ -1539,6 +1539,48 @@ static void pci_restore_ltr_state(struct > > pci_dev *dev) > > pci_write_config_word(dev, ltr + PCI_LTR_MAX_NOSNOOP_LAT, > > *cap++); > > } > > > > +static void pci_save_l1ss_state(struct pci_dev *dev) > > +{ > > + int l1ss; > > + struct pci_cap_saved_state *save_state; > > + u16 *cap; > > + > > + if (!pci_is_pcie(dev)) > > + return; > > + > > + l1ss = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_L1SS); > > + if (!l1ss) > > + return; > > + > > + save_state = pci_find_saved_ext_cap(dev, > > PCI_EXT_CAP_ID_L1SS); > > + if (!save_state) { > > + pci_err(dev, "no suspend buffer for L1 > > Substates\n"); > > + return; > > + } > > + > > + cap = (u16 *)&save_state->cap.data[0]; > > + pci_read_config_word(dev, l1ss + PCI_L1SS_CTL1, cap++); > > + pci_read_config_word(dev, l1ss + PCI_L1SS_CTL1 + 2, cap++); > > + pci_read_config_word(dev, l1ss + PCI_L1SS_CTL2, cap++); > > +} > > + > > +static void pci_restore_l1ss_state(struct pci_dev *dev) > > +{ > > + struct pci_cap_saved_state *save_state; > > + int l1ss; > > + u16 *cap; > > + > > + save_state = pci_find_saved_ext_cap(dev, > > PCI_EXT_CAP_ID_L1SS); > > + l1ss = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_L1SS); > > + if (!save_state || !l1ss) > > + return; > > + > > + cap = (u16 *)&save_state->cap.data[0]; > > + pci_write_config_word(dev, l1ss + PCI_L1SS_CTL1, *cap++); > > + pci_write_config_word(dev, l1ss + PCI_L1SS_CTL1 + 2, > > *cap++); > > + pci_write_config_word(dev, l1ss + PCI_L1SS_CTL2, *cap++); > > +} > > + > > /** > > * pci_save_state - save the PCI configuration space of a device > > before > > * suspending > > @@ -1563,6 +1605,7 @@ int pci_save_state(struct pci_dev *dev) > > if (i != 0) > > return i; > > > > + pci_save_l1ss_state(dev); > > pci_save_ltr_state(dev); > > pci_save_dpc_state(dev); > > pci_save_aer_state(dev); > > @@ -1670,6 +1713,7 @@ void pci_restore_state(struct pci_dev *dev) > > */ > > pci_restore_ltr_state(dev); > > > > + pci_restore_l1ss_state(dev); > > pci_restore_pcie_state(dev); > > pci_restore_pasid_state(dev); > > pci_restore_pri_state(dev); > > @@ -3332,6 +3376,11 @@ 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, > > + 3 * sizeof(u16)); > > + if (error) > > + pci_err(dev, "unable to allocate suspend buffer for > > L1 Substates\n"); > > + > > pci_allocate_vc_save_buffers(dev); > > } > > > > -- > > 2.20.1 > >
