On Wed, Jul 17, 2024 at 03:55:05PM -0500, Wei Huang wrote:
> When "No ST mode" is enabled, endpoint 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.
Capitalize technical terms defined by spec.
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -4656,6 +4656,7 @@
> 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
Needs a little more context here about what this means. Users won't
know where to even look for "No ST Mode" unless they have a copy of
the spec.
> +++ 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())
> + pcie_tph_set_nostmode(pci_dev);
Same comment here; can we do this outside the probe() path somehow?
> return rc;
> }
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 4cbfd5b53be8..8745ce1c4a9a 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);
s/pci/pcie/
Unexport unless it's useful for drivers.
Bjorn
