Commit b0e85c3c authored by Jim Quinlan's avatar Jim Quinlan Committed by Bjorn Helgaas
Browse files

PCI: Add Kconfig options for MPS/MRRS strategy 

Add Kconfig options for changing the default pcie_bus_config, i.e., the
strategy for configuration MPS and MRRS, in the same manner as the
CONFIG_PCIEASPM_XXXX choice.  The pci_bus_config setting may still be
overridden by kernel command-line parameters, e.g.,
"pci=pcie_bus_tune_off".

[bhelgaas: depend on EXPERT, tweak help texts]
Link: https://lore.kernel.org/r/20200928194651.5393-2-james.quinlan@broadcom.com


Signed-off-by: default avatarJim Quinlan <james.quinlan@broadcom.com>
Signed-off-by: default avatarBjorn Helgaas <bhelgaas@google.com>
parent 877c1a5f

drivers/pci/Kconfig

+62 −0
Original line number Diff line number Diff line
@@ -187,6 +187,68 @@ 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 "PCI Express hierarchy optimization setting"

	default PCIE_BUS_DEFAULT

	depends on PCI && EXPERT

	help

	  MPS (Max Payload Size) and MRRS (Max Read Request Size) are PCIe

	  device parameters that affect performance and the ability to

	  support hotplug and peer-to-peer DMA.



	  The following choices set the MPS and MRRS optimization strategy

	  at compile-time.  The choices are the same as those offered for

	  the kernel command-line parameter 'pci', i.e.,

	  'pci=pcie_bus_tune_off', 'pci=pcie_bus_safe',

	  'pci=pcie_bus_perf', and 'pci=pcie_bus_peer2peer'.



	  This is a compile-time setting and can be overridden by the above

	  command-line parameters.  If unsure, choose PCIE_BUS_DEFAULT.



config PCIE_BUS_TUNE_OFF

	bool "Tune Off"

	depends on PCI

	help

	  Use the BIOS defaults; don't touch MPS at all.  This is the same

	  as booting with 'pci=pcie_bus_tune_off'.



config PCIE_BUS_DEFAULT

	bool "Default"

	depends on PCI

	help

	  Default choice; ensure that the MPS matches upstream bridge.



config PCIE_BUS_SAFE

	bool "Safe"

	depends on PCI

	help

	  Use largest MPS that boot-time devices support.  If you have a

	  closed system with no possibility of adding new devices, this

	  will use the largest MPS that's supported by all devices.  This

	  is the same as booting with 'pci=pcie_bus_safe'.



config PCIE_BUS_PERFORMANCE

	bool "Performance"

	depends on PCI

	help

	  Use MPS and MRRS for best performance.  Ensure that a given

	  device's MPS is no larger than its parent MPS, which allows us to

	  keep all switches/bridges to the max MPS supported by their

	  parent.  This is the same as booting with 'pci=pcie_bus_perf'.



config PCIE_BUS_PEER2PEER

	bool "Peer2peer"

	depends on PCI

	help

	  Set MPS = 128 for all devices.  MPS configuration effected by the

	  other options could cause the MPS on one root port to be

	  different than that of the MPS on another, which may cause

	  hot-added devices or peer-to-peer DMA to fail.  Set MPS to the

	  smallest possible value (128B) system-wide to avoid these issues.

	  This is the same as booting with 'pci=pcie_bus_peer2peer'.



endchoice



source "drivers/pci/hotplug/Kconfig"

source "drivers/pci/controller/Kconfig"

source "drivers/pci/endpoint/Kconfig"

drivers/pci/pci.c

+12 −0
Original line number Diff line number Diff line
@@ -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 MPS/MRRS strategy; can be overridden by kernel command-line 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

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