On Tue, Oct 01, 2024 at 04:34:42PM +0800, Jian-Hong Pan wrote: > 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. Then, when it restores the > NVMe's state, ASPM code restores L1SS for both the parent bridge and the > NVMe in pci_restore_aspm_l1ss_state(). The NVMe's L1SS is restored > correctly. But, the parent bridge's L1SS is restored with a wrong value 0x0 > because the parent bridge's L1SS wasn't saved by pci_save_aspm_l1ss_state() > before reset. There's nothing specific to VMD here, is there? This whole log looks like it should be made generic. The VMD *example* is OK, but the justification should not be VMD-specific. This last paragraph seems to be the kernel of the whole thing, and I don't think it's specific to either VMD or NVMe. > 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(). > > Link: https://lore.kernel.org/linux-pci/CAPpJ_eexU0gCHMbXw_z924WxXw0+B6SdS4eG9oGpEX1wmnMLkQ@xxxxxxxxxxxxxx/ > Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218394 > Fixes: 17423360a27a ("PCI/ASPM: Save L1 PM Substates Capability for suspend/resume") > Suggested-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx> > 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() > > v11: > - Introduce __pci_save_aspm_l1ss_state as a resusable helper function > which is same as the original pci_configure_aspm_l1ss > - Make pci_save_aspm_l1ss_state invoke __pci_save_aspm_l1ss_state for > both child and parent devices > - Smooth the commit message > > v12: > - Update the commit message > > drivers/pci/pcie/aspm.c | 20 +++++++++++++++++++- > 1 file changed, 19 insertions(+), 1 deletion(-) > > diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c > index bd0a8a05647e..17cdf372f7e0 100644 > --- a/drivers/pci/pcie/aspm.c > +++ b/drivers/pci/pcie/aspm.c > @@ -79,7 +79,7 @@ void pci_configure_aspm_l1ss(struct pci_dev *pdev) > ERR_PTR(rc)); > } > > -void pci_save_aspm_l1ss_state(struct pci_dev *pdev) > +static void __pci_save_aspm_l1ss_state(struct pci_dev *pdev) > { > struct pci_cap_saved_state *save_state; > u16 l1ss = pdev->l1ss; > @@ -101,6 +101,24 @@ void pci_save_aspm_l1ss_state(struct pci_dev *pdev) > pci_read_config_dword(pdev, l1ss + PCI_L1SS_CTL1, cap++); > } > > +void pci_save_aspm_l1ss_state(struct pci_dev *pdev) > +{ > + struct pci_dev *parent; > + > + __pci_save_aspm_l1ss_state(pdev); Is there any point in saving the "pdev" state if there's no parent? > + /* > + * To be symmetric on pci_restore_aspm_l1ss_state(), save parent's L1 > + * substate configuration, if the parent has not saved state. > + */ > + if (!pdev->bus || !pdev->bus->self) > + return; Is "pdev->bus == NULL" possible here even though it doesn't seem possible in pci_restore_aspm_l1ss_state()? > + parent = pdev->bus->self; > + if (!parent->state_saved) > + __pci_save_aspm_l1ss_state(parent); > +} I see the suggestion for a helper here, but I'm not convinced. pci_save_aspm_l1ss_state() and pci_restore_aspm_l1ss_state() should *look* similar, and a helper makes them less similar. I think you should go to some effort to follow the pci_restore_aspm_l1ss_state() structure, as much as possible doing the same declarations, checks, and lookups in the same order, e.g.: struct pci_cap_saved_state *pl_save_state, *cl_save_state; struct pci_dev *parent = pdev->bus->self; if (pcie_downstream_port(pdev) || !parent) return; if (!pdev->l1ss || !parent->l1ss) return; cl_save_state = pci_find_saved_ext_cap(pdev, PCI_EXT_CAP_ID_L1SS); pl_save_state = pci_find_saved_ext_cap(parent, PCI_EXT_CAP_ID_L1SS); if (!cl_save_state || !pl_save_state) return; Bjorn
