On Wed, 7 Aug 2024, Jian-Hong Pan wrote: > David E. Box <david.e.box@xxxxxxxxxxxxxxx> 於 2024年8月6日 週二 上午4:26寫道： > > > > Hi Jian-Hong, > > > > On Fri, 2024-08-02 at 16:24 +0800, Jian-Hong Pan wrote: > > > Jian-Hong Pan <jhp@xxxxxxxxxxxxx> 於 2024年7月19日 週五 下午4:04寫道： > > > > > > > > Currently, when enable link's L1.2 features with __pci_enable_link_state(), > > > > it configs the link directly without ensuring related L1.2 parameters, such > > > > as T_POWER_ON, Common_Mode_Restore_Time, and LTR_L1.2_THRESHOLD have been > > > > programmed. > > > > > > > > This leads the link's L1.2 between PCIe Root Port and child device gets > > > > wrong configs when a caller tries to enabled it. > > > > > > > > Here is a failed example on ASUS B1400CEAE with enabled VMD: > > > > > > > > 10000:e0:06.0 PCI bridge: Intel Corporation 11th Gen Core Processor PCIe > > > > Controller (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=45us LTR1.2_Threshold=101376ns > > > > L1SubCtl2: T_PwrOn=50us > > > > > > > > 10000:e1:00.0 Non-Volatile memory controller: Sandisk Corp WD Blue SN550 > > > > NVMe SSD (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=0ns > > > > L1SubCtl2: T_PwrOn=10us > > > > > > > > According to "PCIe r6.0, sec 5.5.4", before enabling ASPM L1.2 on the PCIe > > > > Root Port and the child NVMe, they should be programmed with the same > > > > LTR1.2_Threshold value. However, they have different values in this case. > > > > > > > > Invoke aspm_calc_l12_info() to program the L1.2 parameters properly before > > > > enable L1.2 bits of L1 PM Substates Control Register in > > > > __pci_enable_link_state(). > > > > > > > > Link: https://bugzilla.kernel.org/show_bug.cgi?id=218394 > > > > Signed-off-by: Jian-Hong Pan <jhp@xxxxxxxxxxxxx> > > > > --- > > > > v2: > > > > - Prepare the PCIe LTR parameters before enable L1 Substates > > > > > > > > v3: > > > > - Only enable supported features for the L1 Substates part > > > > > > > > v4: > > > > - Focus on fixing L1.2 parameters, instead of re-initializing whole L1SS > > > > > > > > v5: > > > > - Fix typo and commit message > > > > - Split introducing aspm_get_l1ss_cap() to "PCI/ASPM: Introduce > > > > aspm_get_l1ss_cap()" > > > > > > > > v6: > > > > - Skipped > > > > > > > > v7: > > > > - Pick back and rebase on the new version kernel > > > > - Drop the link state flag check. And, always config link state's timing > > > > parameters > > > > > > > > v8: > > > > - Because pcie_aspm_get_link() might return the link as NULL, move > > > > getting the link's parent and child devices after check the link is > > > > not NULL. This avoids NULL memory access. > > > > > > > > drivers/pci/pcie/aspm.c | 15 +++++++++++++++ > > > > 1 file changed, 15 insertions(+) > > > > > > > > diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c > > > > index 5db1044c9895..55ff1d26fcea 100644 > > > > --- a/drivers/pci/pcie/aspm.c > > > > +++ b/drivers/pci/pcie/aspm.c > > > > @@ -1411,9 +1411,15 @@ EXPORT_SYMBOL(pci_disable_link_state); > > > > static int __pci_enable_link_state(struct pci_dev *pdev, int state, bool > > > > locked) > > > > { > > > > struct pcie_link_state *link = pcie_aspm_get_link(pdev); > > > > + u32 parent_l1ss_cap, child_l1ss_cap; > > > > + struct pci_dev *parent, *child; > > > > > > > > if (!link) > > > > return -EINVAL; > > > > + > > > > + parent = link->pdev; > > > > + child = link->downstream; > > > > + > > > > /* > > > > * A driver requested that ASPM be enabled on this device, but > > > > * if we don't have permission to manage ASPM (e.g., on ACPI > > > > @@ -1428,6 +1434,15 @@ static int __pci_enable_link_state(struct pci_dev > > > > *pdev, int state, bool locked) > > > > if (!locked) > > > > down_read(&pci_bus_sem); > > > > mutex_lock(&aspm_lock); > > > > + /* > > > > + * Ensure L1.2 parameters: Common_Mode_Restore_Times, T_POWER_ON and > > > > + * LTR_L1.2_THRESHOLD are programmed properly before enable bits for > > > > + * L1.2, per PCIe r6.0, sec 5.5.4. > > > > + */ > > > > + parent_l1ss_cap = aspm_get_l1ss_cap(parent); > > > > + child_l1ss_cap = aspm_get_l1ss_cap(child); > > > > + aspm_calc_l12_info(link, parent_l1ss_cap, child_l1ss_cap); > > > > I still don't think this is the place to recalculate the L1.2 parameters > > especially when know the calculation was done but was cleared by > > pci_bus_reset(). Can't we just do a pci_save/restore_state() before/after > > pci_bus_reset() in vmd.c? > > I have not thought pci_save/restore_state() around pci_bus_reset() > before. It is an interesting direction. > > So, I prepare modification below for test. Include "[PATCH v8 1/4] > PCI: vmd: Set PCI devices to D0 before enable PCI PM's L1 substates", > too. Then, both the PCIe bridge and the PCIe device have the same > LTR_L1.2_THRESHOLD 101376ns as expected. > > diff --git a/drivers/pci/controller/vmd.c b/drivers/pci/controller/vmd.c > index bbf4a47e7b31..6b8dd4f30127 100644 > --- a/drivers/pci/controller/vmd.c > +++ b/drivers/pci/controller/vmd.c > @@ -727,6 +727,18 @@ static void vmd_copy_host_bridge_flags(struct > pci_host_bridge *root_bridge, > vmd_bridge->native_dpc = root_bridge->native_dpc; > } > > +static int vmd_pci_save_state(struct pci_dev *pdev, void *userdata) > +{ > + pci_save_state(pdev); > + return 0; > +} > + > +static int vmd_pci_restore_state(struct pci_dev *pdev, void *userdata) > +{ > + pci_restore_state(pdev); > + return 0; > +} > + > /* > * Enable ASPM and LTR settings on devices that aren't configured by BIOS. > */ > @@ -927,6 +939,7 @@ static int vmd_enable_domain(struct vmd_dev *vmd, > unsigned long features) > pci_scan_child_bus(vmd->bus); > vmd_domain_reset(vmd); > > + pci_walk_bus(vmd->bus, vmd_pci_save_state, NULL); > /* When Intel VMD is enabled, the OS does not discover the Root Ports > * owned by Intel VMD within the MMCFG space. pci_reset_bus() applies > * a reset to the parent of the PCI device supplied as argument. This > @@ -945,6 +958,7 @@ static int vmd_enable_domain(struct vmd_dev *vmd, > unsigned long features) > break; > } > } > + pci_walk_bus(vmd->bus, vmd_pci_restore_state, NULL); Why not call pci_reset_bus() (or __pci_reset_bus()) then in vmd_enable_domain() which preserves state unlike pci_reset_bus()? (Don't tell me naming of these functions is a horrible mess. :-/) -- i. > > pci_assign_unassigned_bus_resources(vmd->bus); > > > Jian-Hong Pan > > > > > + > > > > link->aspm_default = pci_calc_aspm_enable_mask(state); > > > > pcie_config_aspm_link(link, policy_to_aspm_state(link)); > > > > > > > > -- > > > > 2.45.2 > > > > > > > > > > Hi Nirmal and Paul, > > > > > > It will be great to have your review here. > > > > > > I had tried to "set the threshold value in vmd_pm_enable_quirk()" > > > directly as Paul said [1]. However, it still needs to get the PCIe > > > link from the PCIe device to set the threshold value. > > > And, pci_enable_link_state_locked() gets the link. Then, it will be > > > great to calculate and programm L1 sub-states' parameters properly > > > before configuring the link's ASPM there. > > > > > > [1]: > > > https://lore.kernel.org/linux-kernel/20240624081108.10143-2-jhp@xxxxxxxxxxxxx/T/#mc467498213fe1a6116985c04d714dae378976124 > > > > > > Jian-Hong Pan > > >
