PCI devices' parameters on the VMD bus have been programmed properly
originally. But, cleared after pci_reset_bus() and have not been restored
correctly. This leads the link's L1.2 between PCIe Root Port and child
device gets wrong configs.
Here is a failed example on ASUS B1400CEAE with enabled VMD. Both PCIe
bridge and NVMe device should have the same LTR1.2_Threshold value.
However, they are configured as different values in this case:
10000:e0:06.0 PCI bridge [0604]: Intel Corporation 11th Gen Core Processor PCIe Controller [8086:9a09] (rev 01) (prog-if 00 [Normal decode])
...
Capabilities: [200 v1] L1 PM Substates
L1SubCap: PCI-PM_L1.2+ PCI-PM_L1.1+ ASPM_L1.2+ ASPM_L1.1+ L1_PM_Substates+
PortCommonModeRestoreTime=45us PortTPowerOnTime=50us
L1SubCtl1: PCI-PM_L1.2- PCI-PM_L1.1- ASPM_L1.2+ ASPM_L1.1-
T_CommonMode=0us LTR1.2_Threshold=0ns
L1SubCtl2: T_PwrOn=0us
10000:e1:00.0 Non-Volatile memory controller [0108]: Sandisk Corp WD Blue SN550 NVMe SSD [15b7:5009] (rev 01) (prog-if 02 [NVM Express])
...
Capabilities: [900 v1] L1 PM Substates
L1SubCap: PCI-PM_L1.2+ PCI-PM_L1.1- ASPM_L1.2+ ASPM_L1.1- L1_PM_Substates+
PortCommonModeRestoreTime=32us PortTPowerOnTime=10us
L1SubCtl1: PCI-PM_L1.2- PCI-PM_L1.1- ASPM_L1.2+ ASPM_L1.1-
T_CommonMode=0us LTR1.2_Threshold=101376ns
L1SubCtl2: T_PwrOn=50us
Here is VMD mapped PCI device tree:
-+-[0000:00]-+-00.0 Intel Corporation Device 9a04
| ...
\-[10000:e0]-+-06.0-[e1]----00.0 Sandisk Corp WD Blue SN550 NVMe SSD
\-17.0 Intel Corporation Tiger Lake-LP SATA Controller
When pci_reset_bus() resets the bus [e1] of the NVMe, it only saves and
restores NVMe's state before and after reset. Because bus [e1] has only one
device: 10000:e1:00.0 NVMe. The PCIe bridge is missed. However, when it
restores the NVMe's state, it also restores the ASPM L1SS between the PCIe
bridge and the NVMe by pci_restore_aspm_l1ss_state(). The NVMe's L1SS is
restored correctly. But, the PCIe bridge's L1SS is restored with the wrong
value 0x0 [1]. Because, the parent device (PCIe bridge)'s L1SS is not saved
by pci_save_aspm_l1ss_state() before reset. That is why
pci_restore_aspm_l1ss_state() gets the parent device (PCIe bridge)'s saved
state capability data and restores L1SS with value 0.
So, if the PCI device has a parent, make pci_save_aspm_l1ss_state() save
the parent's L1SS configuration, too. This is symmetric on
pci_restore_aspm_l1ss_state().
[1]: https://lore.kernel.org/linux-pci/CAPpJ_eexU0gCHMbXw_z924WxXw0+B6SdS4eG9oGpEX1wmnMLkQ@xxxxxxxxxxxxxx/
Link: https://bugzilla.kernel.org/show_bug.cgi?id=218394
Signed-off-by: Jian-Hong Pan <jhp@xxxxxxxxxxxxx>
---
v9:
- Drop the v8 fix about drivers/pci/pcie/aspm.c. Use this in VMD instead.
v10:
- Drop the v9 fix about drivers/pci/controller/vmd.c
- Fix in PCIe ASPM to make it symmetric between pci_save_aspm_l1ss_state()
and pci_restore_aspm_l1ss_state()
drivers/pci/pcie/aspm.c | 39 +++++++++++++++++++++++++++++++--------
1 file changed, 31 insertions(+), 8 deletions(-)
diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index bd0a8a05647e..823aaf813978 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -81,24 +81,47 @@ void pci_configure_aspm_l1ss(struct pci_dev *pdev)
void pci_save_aspm_l1ss_state(struct pci_dev *pdev)
{
- struct pci_cap_saved_state *save_state;
- u16 l1ss = pdev->l1ss;
+ struct pci_cap_saved_state *pl_save_state, *cl_save_state;
+ struct pci_dev *parent;
u32 *cap;
/*
* Save L1 substate configuration. The ASPM L0s/L1 configuration
* in PCI_EXP_LNKCTL_ASPMC is saved by pci_save_pcie_state().
*/
- if (!l1ss)
+ if (!pdev->l1ss)
return;
- save_state = pci_find_saved_ext_cap(pdev, PCI_EXT_CAP_ID_L1SS);
- if (!save_state)
+ cl_save_state = pci_find_saved_ext_cap(pdev, PCI_EXT_CAP_ID_L1SS);
+ if (!cl_save_state)
return;
- cap = &save_state->cap.data[0];
- pci_read_config_dword(pdev, l1ss + PCI_L1SS_CTL2, cap++);
- pci_read_config_dword(pdev, l1ss + PCI_L1SS_CTL1, cap++);
+ cap = &cl_save_state->cap.data[0];
+ pci_read_config_dword(pdev, pdev->l1ss + PCI_L1SS_CTL2, cap++);
+ pci_read_config_dword(pdev, pdev->l1ss + PCI_L1SS_CTL1, cap++);
+
+ /*
+ * If here is a parent device and it has not saved state, save parent's
+ * L1 substate configuration, too. This is symmetric on
+ * pci_restore_aspm_l1ss_state().
+ */
+ if (!pdev->bus || !pdev->bus->self)
+ return;
+
+ parent = pdev->bus->self;
+ if (!parent->l1ss)
+ return;
+
+ pl_save_state = pci_find_saved_ext_cap(parent, PCI_EXT_CAP_ID_L1SS);
+ if (!pl_save_state)
+ return;
+
+ if (parent->state_saved)
+ return;
+
+ cap = &pl_save_state->cap.data[0];
+ pci_read_config_dword(parent, parent->l1ss + PCI_L1SS_CTL2, cap++);
+ pci_read_config_dword(parent, parent->l1ss + PCI_L1SS_CTL1, cap++);
}
void pci_restore_aspm_l1ss_state(struct pci_dev *pdev)
--
2.46.2
