On Tue, Sep 08, 2020 at 12:32:48PM -0400, Jim Quinlan wrote: > The Kconfig is modified so that the pcie_bus_config setting can be done at > build time in the same manner as the CONFIG_PCIEASPM_XXXX choice. The > pci_bus_config setting may still be overridden by the bootline param. I guess... I really hate these build-time config settings for both ASPM and MPS/MRRS. But Linux just isn't smart or flexible enough to do the right thing at run-time, so I guess we're kind of stuck. I guess you have systems where you need a different default? It'd be nice if we could put a little more detail in the Kconfig to help users choose the correct one. "Ensure MPS matches upstream bridge" is *accurate*, but it doesn't really tell me why I would choose this rather than a different one. Maybe we could mention the corresponding command-line parameters, e.g., "This is the same as booting with 'pci=pcie_bus_tune_off'"? > Signed-off-by: Jim Quinlan <james.quinlan@xxxxxxxxxxxx> > --- > drivers/pci/Kconfig | 40 ++++++++++++++++++++++++++++++++++++++++ > drivers/pci/pci.c | 12 ++++++++++++ > 2 files changed, 52 insertions(+) > > diff --git a/drivers/pci/Kconfig b/drivers/pci/Kconfig > index 4bef5c2bae9f..efe69b0d9f7f 100644 > --- a/drivers/pci/Kconfig > +++ b/drivers/pci/Kconfig > @@ -187,6 +187,46 @@ config PCI_HYPERV > The PCI device frontend driver allows the kernel to import arbitrary > PCI devices from a PCI backend to support PCI driver domains. > > +choice > + prompt "PCIE default bus config setting" > + default PCIE_BUS_DEFAULT > + depends on PCI > + help > + One of the following choices will set the pci_bus_config at > + compile time. This will still be overridden by the appropriate > + pci bootline parameter. > + > +config PCIE_BUS_TUNE_OFF > + bool "Tune Off" > + depends on PCI > + help > + Use the BIOS defaults; doesn't touch MPS at all. > + > +config PCIE_BUS_DEFAULT > + bool "Default" > + depends on PCI > + help > + Ensure MPS matches upstream bridge. > + > +config PCIE_BUS_SAFE > + bool "Safe" > + depends on PCI > + help > + Use largest MPS boot-time devices support. > + > +config PCIE_BUS_PERFORMANCE > + bool "Performance" > + depends on PCI > + help > + Use MPS and MRRS for best performance. > + > +config PCIE_BUS_PEER2PEER > + bool "Peer2peer" > + depends on PCI > + help > + Set MPS = 128 for all devices. > +endchoice > + > source "drivers/pci/hotplug/Kconfig" > source "drivers/pci/controller/Kconfig" > source "drivers/pci/endpoint/Kconfig" > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c > index e39c5499770f..dfb52ed4a931 100644 > --- a/drivers/pci/pci.c > +++ b/drivers/pci/pci.c > @@ -101,7 +101,19 @@ unsigned long pci_hotplug_mmio_pref_size = DEFAULT_HOTPLUG_MMIO_PREF_SIZE; > #define DEFAULT_HOTPLUG_BUS_SIZE 1 > unsigned long pci_hotplug_bus_size = DEFAULT_HOTPLUG_BUS_SIZE; > > + > +/* PCIE bus config, can be overridden by bootline param */ > +#ifdef CONFIG_PCIE_BUS_TUNE_OFF > +enum pcie_bus_config_types pcie_bus_config = PCIE_BUS_TUNE_OFF; > +#elif defined CONFIG_PCIE_BUS_SAFE > +enum pcie_bus_config_types pcie_bus_config = PCIE_BUS_SAFE; > +#elif defined CONFIG_PCIE_BUS_PERFORMANCE > +enum pcie_bus_config_types pcie_bus_config = PCIE_BUS_PERFORMANCE; > +#elif defined CONFIG_PCIE_BUS_PEER2PEER > +enum pcie_bus_config_types pcie_bus_config = PCIE_BUS_PEER2PEER; > +#else > enum pcie_bus_config_types pcie_bus_config = PCIE_BUS_DEFAULT; > +#endif > > /* > * The default CLS is used if arch didn't set CLS explicitly and not > -- > 2.17.1 >
