Hi, On Fri, Jan 29, 2021 at 03:11:37PM +0800, [email protected] wrote: > From: Mingchuang Qiao <[email protected]> > > In bus scan flow, the "LTR Mechanism Enable" bit of DEVCTL2 register is > configured in pci_configure_ltr(). If device and bridge both support LTR > mechanism, the "LTR Mechanism Enable" bit of device and bridge will be > enabled in DEVCTL2 register. And pci_dev->ltr_path will be set as 1. > > If PCIe link goes down when device resets, the "LTR Mechanism Enable" bit > of bridge will change to 0 according to PCIe r5.0, sec 7.5.3.16. However, > the pci_dev->ltr_path value of bridge is still 1. > > For following conditions, check and re-configure "LTR Mechanism Enable" bit > of bridge to make "LTR Mechanism Enable" bit mtach ltr_path value.
Typo mtach -> match. > -before configuring device's LTR for hot-remove/hot-add > -before restoring device's DEVCTL2 register when restore device state > > Signed-off-by: Mingchuang Qiao <[email protected]> > --- > changes of v2 > -modify patch description > -reconfigure bridge's LTR before restoring device DEVCTL2 register > changes of v3 > -call pci_reconfigure_bridge_ltr() in probe.c Hmm, which part of this patch takes care of the reset path? It is not entirely clear to me at least. > --- > drivers/pci/pci.c | 25 +++++++++++++++++++++++++ > drivers/pci/pci.h | 1 + > drivers/pci/probe.c | 13 ++++++++++--- > 3 files changed, 36 insertions(+), 3 deletions(-) > > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c > index b9fecc25d213..12b557c8f062 100644 > --- a/drivers/pci/pci.c > +++ b/drivers/pci/pci.c > @@ -1437,6 +1437,24 @@ static int pci_save_pcie_state(struct pci_dev *dev) > return 0; > } > > +void pci_reconfigure_bridge_ltr(struct pci_dev *dev) > +{ > +#ifdef CONFIG_PCIEASPM > + struct pci_dev *bridge; > + u32 ctl; > + > + bridge = pci_upstream_bridge(dev); > + if (bridge && bridge->ltr_path) { > + pcie_capability_read_dword(bridge, PCI_EXP_DEVCTL2, &ctl); > + if (!(ctl & PCI_EXP_DEVCTL2_LTR_EN)) { > + pci_dbg(bridge, "re-enabling LTR\n"); > + pcie_capability_set_word(bridge, PCI_EXP_DEVCTL2, > + PCI_EXP_DEVCTL2_LTR_EN); > + } > + } > +#endif > +} > + > static void pci_restore_pcie_state(struct pci_dev *dev) > { > int i = 0; > @@ -1447,6 +1465,13 @@ static void pci_restore_pcie_state(struct pci_dev *dev) > if (!save_state) > return; > > + /* > + * Downstream ports reset the LTR enable bit when link goes down. > + * Check and re-configure the bit here before restoring device. > + * PCIe r5.0, sec 7.5.3.16. > + */ > + pci_reconfigure_bridge_ltr(dev); > + > cap = (u16 *)&save_state->cap.data[0]; > pcie_capability_write_word(dev, PCI_EXP_DEVCTL, cap[i++]); > pcie_capability_write_word(dev, PCI_EXP_LNKCTL, cap[i++]); > diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h > index 5c59365092fa..a660a01358c5 100644 > --- a/drivers/pci/pci.h > +++ b/drivers/pci/pci.h > @@ -111,6 +111,7 @@ void pci_free_cap_save_buffers(struct pci_dev *dev); > bool pci_bridge_d3_possible(struct pci_dev *dev); > void pci_bridge_d3_update(struct pci_dev *dev); > void pci_bridge_wait_for_secondary_bus(struct pci_dev *dev); > +void pci_reconfigure_bridge_ltr(struct pci_dev *dev); Nit: calling it pci_bridge_reconfigure_ltr() would match better with the other function names. > > static inline void pci_wakeup_event(struct pci_dev *dev) > { > diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c > index 953f15abc850..fa6075093f3b 100644 > --- a/drivers/pci/probe.c > +++ b/drivers/pci/probe.c > @@ -2132,9 +2132,16 @@ static void pci_configure_ltr(struct pci_dev *dev) > * Complex and all intermediate Switches indicate support for LTR. > * PCIe r4.0, sec 6.18. > */ > - if (pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT || > - ((bridge = pci_upstream_bridge(dev)) && > - bridge->ltr_path)) { > + if (pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT) { > + pcie_capability_set_word(dev, PCI_EXP_DEVCTL2, > + PCI_EXP_DEVCTL2_LTR_EN); > + dev->ltr_path = 1; > + return; > + } > + > + bridge = pci_upstream_bridge(dev); > + if (bridge && bridge->ltr_path) { > + pci_reconfigure_bridge_ltr(dev); > pcie_capability_set_word(dev, PCI_EXP_DEVCTL2, > PCI_EXP_DEVCTL2_LTR_EN); > dev->ltr_path = 1; > -- > 2.18.0
