linux-kernel - [PATCH v2 1/1] PCI: pcie_bus_config can be set at build time

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Message-Id: <20200916145707.33313-2-james.quinlan@broadcom.com>
Date:   Wed, 16 Sep 2020 10:57:06 -0400
From:   Jim Quinlan <james.quinlan@...adcom.com>
To:     linux-pci@...r.kernel.org, bcm-kernel-feedback-list@...adcom.com,
        james.quinlan@...adcom.com
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>,
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH v2 1/1] PCI: pcie_bus_config can be set at build time

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.

Signed-off-by: Jim Quinlan <james.quinlan@...adcom.com>
---
 drivers/pci/Kconfig | 56 +++++++++++++++++++++++++++++++++++++++++++++
 drivers/pci/pci.c   | 12 ++++++++++
 2 files changed, 68 insertions(+)

diff --git a/drivers/pci/Kconfig b/drivers/pci/Kconfig
index 4bef5c2bae9f..15ce948858fb 100644
--- a/drivers/pci/Kconfig
+++ b/drivers/pci/Kconfig
@@ -187,6 +187,62 @@ 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.  The choices offered are the same as those offered
+	  for the bootline 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 is still be overridden by the
+	  above bootline parameters, if present.  If unsure, chose PCIE_BUS_DEFAULT.
+
+config PCIE_BUS_TUNE_OFF
+	bool "Tune Off"
+	depends on PCI
+	help
+	  Use the BIOS defaults; doesn'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; ensures 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.  This setting ensures
+	  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 and eventually the PHB.  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.  Simply making the system
+	  wide MPS be set to the smallest possible value (128B) solves
+	  this issue.  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"
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


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