PCI: Add pci=alloc_high support

add pci=alloc_high to enable/disable alloc_high for resource allcation.

default to alloc high to disable.

Signed-off-by: Yinghai Lu <yinghai@kernel.org>

4 files changed, 23 insertions, 0 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index ad7e2e5088c12..56065b06a1671 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2189,6 +2189,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 				off: Turn realloc off
 				on: Turn realloc on
 		realloc		same as realloc=on
+		alloc_high=	Enable/disable allocating PCI resources above
+				4G at first when allocating resource to PCI
+				devices that does not get assigned by BIOS.
+				off: Turn alloc_high off
+				on: Turn alloc_high on
+		alloc_high	same as alloc_high=on
 		noari		do not use PCIe ARI.
 		pcie_scan_all	Scan all possible PCIe devices.  Otherwise we
 				only look for one device below a PCIe downstream
diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c
index b4aae0f086ccf..264c4522b75b1 100644
--- a/drivers/pci/bus.c
+++ b/drivers/pci/bus.c
@@ -98,6 +98,14 @@ void pci_bus_remove_resources(struct pci_bus *bus)
 	}
 }
 
+static bool pci_alloc_high_enable = false;
+void __init pci_alloc_high_get_opt(char *str)
+{
+	if (!strncmp(str, "off", 3))
+		pci_alloc_high_enable = false;
+	else if (!strncmp(str, "on", 2))
+		pci_alloc_high_enable = true;
+}
 /**
  * pci_bus_alloc_resource - allocate a resource from a parent bus
  * @bus: PCI bus
@@ -147,6 +155,8 @@ pci_bus_alloc_resource(struct pci_bus *bus, struct resource *res,
 
 		start = 0;
 		end = MAX_RESOURCE;
+		if (!pci_alloc_high_enable)
+			goto again;
 		/*
 		 * don't allocate too high if the pref mem doesn't
 		 * support 64bit, also if this is a 64-bit mem
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 6b0a9aef1faa8..34d6da045f5c1 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -3871,6 +3871,10 @@ static int __init pci_setup(char *str)
 				pci_realloc_get_opt(str + 8);
 			} else if (!strncmp(str, "realloc", 7)) {
 				pci_realloc_get_opt("on");
+			} else if (!strncmp(str, "alloc_high=", 11)) {
+				pci_alloc_high_get_opt(str + 11);
+			} else if (!strncmp(str, "alloc_high", 10)) {
+				pci_alloc_high_get_opt("on");
 			} else if (!strcmp(str, "nodomains")) {
 				pci_no_domains();
 			} else if (!strncmp(str, "noari", 5)) {
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 0697604c71b6c..d4e05b735370a 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -145,6 +145,7 @@ static inline void pci_msi_init_pci_dev(struct pci_dev *dev) { }
 #endif
 
 void pci_realloc_get_opt(char *);
+void pci_alloc_high_get_opt(char *);
 
 static inline int pci_no_d1d2(struct pci_dev *dev)
 {
@@ -205,6 +206,8 @@ enum pci_bar_type {
 
 #define PCI_MAX_ADDR_32	((resource_size_t)0xffffffff)
 
+#define PCI_MAX_ADDR_32	((resource_size_t)0xffffffff)
+
 bool pci_bus_read_dev_vendor_id(struct pci_bus *bus, int devfn, u32 *pl,
 				int crs_timeout);
 extern int pci_setup_device(struct pci_dev *dev);