| Message ID | 20240531213841.3246055-5-wei.huang2@amd.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Bjorn Helgaas |
| Headers | show |
| Series | PCIe TPH and cache direct injection support | expand |
On Fri, 31 May 2024 16:38:36 -0500 Wei Huang <wei.huang2@amd.com> wrote: > When "No ST mode" is enabled, end-point devices can generate TPH headers > but with all steering tags treated as zero. A steering tag of zero is > interpreted as "using the default policy" by the root complex. This is > essential to quantify the benefit of steering tags for some given > workloads. This is a good explanation. Need similar in the previous patch to justify the disable TPH entirely. > diff --git a/drivers/pci/pcie/tph.c b/drivers/pci/pcie/tph.c > index 5dc533b89a33..d5f7309fdf52 100644 > --- a/drivers/pci/pcie/tph.c > +++ b/drivers/pci/pcie/tph.c > @@ -43,6 +43,27 @@ static int tph_set_reg_field_u32(struct pci_dev *dev, u8 offset, u32 mask, > return ret; > } > > +int tph_set_dev_nostmode(struct pci_dev *dev) > +{ > + int ret; > + > + /* set ST Mode Select to "No ST Mode" */ > + ret = tph_set_reg_field_u32(dev, PCI_TPH_CTRL, > + PCI_TPH_CTRL_MODE_SEL_MASK, > + PCI_TPH_CTRL_MODE_SEL_SHIFT, > + PCI_TPH_NO_ST_MODE); > + if (ret) > + return ret; > + > + /* set "TPH Requester Enable" to "TPH only" */ > + ret = tph_set_reg_field_u32(dev, PCI_TPH_CTRL, > + PCI_TPH_CTRL_REQ_EN_MASK, > + PCI_TPH_CTRL_REQ_EN_SHIFT, > + PCI_TPH_REQ_TPH_ONLY); Unless these have to be two RMW operations. (if they do add a spec reference) then this is a good example of why a field update function may not be the right option. We probably want to RMW once. return tph_set_reg_field_u32() > + > + return ret; > +} > + > int pcie_tph_disable(struct pci_dev *dev) > { > return tph_set_reg_field_u32(dev, PCI_TPH_CTRL,
On Fri, May 31, 2024 at 04:38:36PM -0500, Wei Huang wrote: > When "No ST mode" is enabled, end-point devices can generate TPH headers > but with all steering tags treated as zero. A steering tag of zero is > interpreted as "using the default policy" by the root complex. This is > essential to quantify the benefit of steering tags for some given > workloads. > #ifdef CONFIG_PCIE_TPH > int pcie_tph_disable(struct pci_dev *dev); > +int tph_set_dev_nostmode(struct pci_dev *dev); Exported functions need a "pci" or "pcie_" prefix. We haven't been completely consistent on this; we have "pci_acs_*", which is obviously PCIe-specific, but we do also have pcie_find_root_port() etc.
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index fedcc69e35c1..e97a4a239563 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -4624,6 +4624,7 @@ norid [S390] ignore the RID field and force use of one PCI domain per PCI function notph [PCIE] Do not use PCIe TPH + nostmode [PCIE] Force TPH to use No ST Mode pcie_aspm= [PCIE] Forcibly enable or ignore PCIe Active State Power Management. diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c index 9722d070c0ca..aa98843d9884 100644 --- a/drivers/pci/pci-driver.c +++ b/drivers/pci/pci-driver.c @@ -324,8 +324,13 @@ static long local_pci_probe(void *_ddi) pci_dev->driver = pci_drv; rc = pci_drv->probe(pci_dev, ddi->id); if (!rc) { - if (pci_tph_disabled()) + if (pci_tph_disabled()) { pcie_tph_disable(pci_dev); + return rc; + } + + if (pci_tph_nostmode()) + tph_set_dev_nostmode(pci_dev); return rc; } diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index 31c443504ce9..f3558a551bf2 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -160,6 +160,9 @@ static bool pcie_ats_disabled; /* If set, the PCIe TPH capability will not be used. */ static bool pcie_tph_disabled; +/* If TPH is enabled, "No ST Mode" will be enforced. */ +static bool pcie_tph_nostmode; + /* If set, the PCI config space of each device is printed during boot. */ bool pci_early_dump; @@ -175,6 +178,12 @@ bool pci_tph_disabled(void) } EXPORT_SYMBOL_GPL(pci_tph_disabled); +bool pci_tph_nostmode(void) +{ + return pcie_tph_nostmode; +} +EXPORT_SYMBOL_GPL(pci_tph_nostmode); + /* Disable bridge_d3 for all PCIe ports */ static bool pci_bridge_d3_disable; /* Force bridge_d3 for all PCIe ports */ @@ -6818,6 +6827,9 @@ static int __init pci_setup(char *str) } else if (!strcmp(str, "notph")) { pr_info("PCIe: TPH is disabled\n"); pcie_tph_disabled = true; + } else if (!strcmp(str, "nostmode")) { + pr_info("PCIe: TPH No ST Mode is enabled\n"); + pcie_tph_nostmode = true; } else if (!strncmp(str, "cbiosize=", 9)) { pci_cardbus_io_size = memparse(str + 9, &str); } else if (!strncmp(str, "cbmemsize=", 10)) { diff --git a/drivers/pci/pcie/tph.c b/drivers/pci/pcie/tph.c index 5dc533b89a33..d5f7309fdf52 100644 --- a/drivers/pci/pcie/tph.c +++ b/drivers/pci/pcie/tph.c @@ -43,6 +43,27 @@ static int tph_set_reg_field_u32(struct pci_dev *dev, u8 offset, u32 mask, return ret; } +int tph_set_dev_nostmode(struct pci_dev *dev) +{ + int ret; + + /* set ST Mode Select to "No ST Mode" */ + ret = tph_set_reg_field_u32(dev, PCI_TPH_CTRL, + PCI_TPH_CTRL_MODE_SEL_MASK, + PCI_TPH_CTRL_MODE_SEL_SHIFT, + PCI_TPH_NO_ST_MODE); + if (ret) + return ret; + + /* set "TPH Requester Enable" to "TPH only" */ + ret = tph_set_reg_field_u32(dev, PCI_TPH_CTRL, + PCI_TPH_CTRL_REQ_EN_MASK, + PCI_TPH_CTRL_REQ_EN_SHIFT, + PCI_TPH_REQ_TPH_ONLY); + + return ret; +} + int pcie_tph_disable(struct pci_dev *dev) { return tph_set_reg_field_u32(dev, PCI_TPH_CTRL, diff --git a/include/linux/pci-tph.h b/include/linux/pci-tph.h index e187d7e89e8c..95269afc8b7d 100644 --- a/include/linux/pci-tph.h +++ b/include/linux/pci-tph.h @@ -11,9 +11,12 @@ #ifdef CONFIG_PCIE_TPH int pcie_tph_disable(struct pci_dev *dev); +int tph_set_dev_nostmode(struct pci_dev *dev); #else static inline int pcie_tph_disable(struct pci_dev *dev) { return -EOPNOTSUPP; } +static inline int tph_set_dev_nostmode(struct pci_dev *dev) +{ return -EOPNOTSUPP; } #endif #endif /* LINUX_PCI_TPH_H */ diff --git a/include/linux/pci.h b/include/linux/pci.h index d88ebe87815a..5f520624d133 100644 --- a/include/linux/pci.h +++ b/include/linux/pci.h @@ -1842,6 +1842,7 @@ static inline bool pci_aer_available(void) { return false; } bool pci_ats_disabled(void); bool pci_tph_disabled(void); +bool pci_tph_nostmode(void); #ifdef CONFIG_PCIE_PTM int pci_enable_ptm(struct pci_dev *dev, u8 *granularity);