| Message ID | 20210128100531.2694-1-mingchuang.qiao@mediatek.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [v2] PCI: Avoid unsync of LTR mechanism configuration | expand |
Hi, On Thu, Jan 28, 2021 at 06:05:31PM +0800, mingchuang.qiao@mediatek.com wrote: > From: Mingchuang Qiao <mingchuang.qiao@mediatek.com> > > 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. > -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 <mingchuang.qiao@mediatek.com> > --- > changes of v2 > -modify patch description > -reconfigure bridge's LTR before restoring device DEVCTL2 register > --- > drivers/pci/pci.c | 25 +++++++++++++++++++++++++ > drivers/pci/probe.c | 19 ++++++++++++++++--- > 2 files changed, 41 insertions(+), 3 deletions(-) > > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c > index b9fecc25d213..88b4eb70c252 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; > } > > +static 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/probe.c b/drivers/pci/probe.c > index 953f15abc850..4ad172517fd2 100644 > --- a/drivers/pci/probe.c > +++ b/drivers/pci/probe.c > @@ -2132,9 +2132,22 @@ 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) { > + 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); > + } > + Can't you use pci_reconfigure_bridge_ltr() here too? Otherwise looks good.
On Thu, 2021-01-28 at 16:27 +0200, Mika Westerberg wrote: > Hi, > > On Thu, Jan 28, 2021 at 06:05:31PM +0800, mingchuang.qiao@mediatek.com wrote: > > From: Mingchuang Qiao <mingchuang.qiao@mediatek.com> > > > > 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. > > -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 <mingchuang.qiao@mediatek.com> > > --- > > changes of v2 > > -modify patch description > > -reconfigure bridge's LTR before restoring device DEVCTL2 register > > --- > > drivers/pci/pci.c | 25 +++++++++++++++++++++++++ > > drivers/pci/probe.c | 19 ++++++++++++++++--- > > 2 files changed, 41 insertions(+), 3 deletions(-) > > > > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c > > index b9fecc25d213..88b4eb70c252 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; > > } > > > > +static 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/probe.c b/drivers/pci/probe.c > > index 953f15abc850..4ad172517fd2 100644 > > --- a/drivers/pci/probe.c > > +++ b/drivers/pci/probe.c > > @@ -2132,9 +2132,22 @@ 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) { > > + 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); > > + } > > + > > Can't you use pci_reconfigure_bridge_ltr() here too? > > Otherwise looks good. Thanks for review. I have sent a new patch for this. https://lore.kernel.org/linux-arm-kernel/20210129071137.8743-1-mingchuang.qiao@mediatek.com/
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index b9fecc25d213..88b4eb70c252 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; } +static 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/probe.c b/drivers/pci/probe.c index 953f15abc850..4ad172517fd2 100644 --- a/drivers/pci/probe.c +++ b/drivers/pci/probe.c @@ -2132,9 +2132,22 @@ 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) { + 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); + } + pcie_capability_set_word(dev, PCI_EXP_DEVCTL2, PCI_EXP_DEVCTL2_LTR_EN); dev->ltr_path = 1;