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
