[PATCH v3 1/2] PCI: Add __pci_bus_alloc_resource() to allocate with explicit flags

[Ard Biesheuvel <ardb+git@google.com>]

From: Ard Biesheuvel <ardb@kernel.org>

pci_bus_alloc_resource() decides which bus resources a resource may be
allocated from based on the flags of that resource: the type bits
selected by @type_mask must match, a non-prefetchable resource is never
allocated from a prefetchable bus resource, and only a 64-bit resource
may be placed above 4 GB.

In preparation for placing some non-prefetchable BARs in prefetchable
bridge windows, factor out __pci_bus_alloc_resource(), which takes the
flags to match against the bus resources as a separate argument, and
implement pci_bus_alloc_resource() on top of it by passing the flags of
the resource itself.

No functional change intended.

Assisted-by: LLM
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 drivers/pci/bus.c | 70 ++++++++++++++------
 drivers/pci/pci.h |  6 ++
 2 files changed, 54 insertions(+), 22 deletions(-)

diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c
index 655ed53436d3..65a54d6e049e 100644
--- a/drivers/pci/bus.c
+++ b/drivers/pci/bus.c
@@ -188,9 +188,9 @@ static void pci_clip_resource_to_region(struct pci_bus *bus,
 }
 
 static int pci_bus_alloc_from_region(struct pci_bus *bus, struct resource *res,
-		resource_size_t size, resource_size_t align,
-		resource_size_t min, unsigned long type_mask,
-		resource_alignf alignf,
+		unsigned long flags, resource_size_t size,
+		resource_size_t align, resource_size_t min,
+		unsigned long type_mask, resource_alignf alignf,
 		void *alignf_data,
 		struct pci_bus_region *region)
 {
@@ -210,13 +210,13 @@ static int pci_bus_alloc_from_region(struct pci_bus *bus, struct resource *res,
 			continue;
 
 		/* type_mask must match */
-		if ((res->flags ^ r->flags) & type_mask)
+		if ((flags ^ r->flags) & type_mask)
 			continue;
 
 		/* We cannot allocate a non-prefetching resource
 		   from a pre-fetching area */
 		if ((r->flags & IORESOURCE_PREFETCH) &&
-		    !(res->flags & IORESOURCE_PREFETCH))
+		    !(flags & IORESOURCE_PREFETCH))
 			continue;
 
 		avail = *r;
@@ -247,9 +247,10 @@ static int pci_bus_alloc_from_region(struct pci_bus *bus, struct resource *res,
 }
 
 /**
- * pci_bus_alloc_resource - allocate a resource from a parent bus
+ * __pci_bus_alloc_resource - allocate a resource from a parent bus
  * @bus: PCI bus
  * @res: resource to allocate
+ * @flags: resource flags to match against the bus resources
  * @size: size of resource to allocate
  * @align: alignment of resource to allocate
  * @min: minimum /proc/iomem address to allocate
@@ -257,36 +258,61 @@ static int pci_bus_alloc_from_region(struct pci_bus *bus, struct resource *res,
  * @alignf: resource alignment function
  * @alignf_data: data argument for resource alignment function
  *
- * Given the PCI bus a device resides on, the size, minimum address,
- * alignment and type, try to find an acceptable resource allocation
- * for a specific device resource.
+ * Like pci_bus_alloc_resource(), but match the bus resources against @flags
+ * rather than @res->flags. This permits allocating a non-prefetchable
+ * resource from a prefetchable bus resource by passing @flags with
+ * IORESOURCE_PREFETCH set, which the caller must have established to be safe.
  */
-int pci_bus_alloc_resource(struct pci_bus *bus, struct resource *res,
-		resource_size_t size, resource_size_t align,
-		resource_size_t min, unsigned long type_mask,
-		resource_alignf alignf,
-		void *alignf_data)
+int __pci_bus_alloc_resource(struct pci_bus *bus, struct resource *res,
+			     unsigned long flags, resource_size_t size,
+			     resource_size_t align, resource_size_t min,
+			     unsigned long type_mask, resource_alignf alignf,
+			     void *alignf_data)
 {
 #ifdef CONFIG_ARCH_DMA_ADDR_T_64BIT
 	int rc;
 
-	if (res->flags & IORESOURCE_MEM_64) {
-		rc = pci_bus_alloc_from_region(bus, res, size, align, min,
-					       type_mask, alignf, alignf_data,
-					       &pci_high);
+	if (flags & IORESOURCE_MEM_64) {
+		rc = pci_bus_alloc_from_region(bus, res, flags, size, align,
+					       min, type_mask, alignf,
+					       alignf_data, &pci_high);
 		if (rc == 0)
 			return 0;
 
-		return pci_bus_alloc_from_region(bus, res, size, align, min,
-						 type_mask, alignf, alignf_data,
-						 &pci_64_bit);
+		return pci_bus_alloc_from_region(bus, res, flags, size, align,
+						 min, type_mask, alignf,
+						 alignf_data, &pci_64_bit);
 	}
 #endif
 
-	return pci_bus_alloc_from_region(bus, res, size, align, min,
+	return pci_bus_alloc_from_region(bus, res, flags, size, align, min,
 					 type_mask, alignf, alignf_data,
 					 &pci_32_bit);
 }
+
+/**
+ * pci_bus_alloc_resource - allocate a resource from a parent bus
+ * @bus: PCI bus
+ * @res: resource to allocate
+ * @size: size of resource to allocate
+ * @align: alignment of resource to allocate
+ * @min: minimum /proc/iomem address to allocate
+ * @type_mask: IORESOURCE_* type flags
+ * @alignf: resource alignment function
+ * @alignf_data: data argument for resource alignment function
+ *
+ * Given the PCI bus a device resides on, the size, minimum address,
+ * alignment and type, try to find an acceptable resource allocation
+ * for a specific device resource.
+ */
+int pci_bus_alloc_resource(struct pci_bus *bus, struct resource *res,
+			   resource_size_t size, resource_size_t align,
+			   resource_size_t min, unsigned long type_mask,
+			   resource_alignf alignf, void *alignf_data)
+{
+	return __pci_bus_alloc_resource(bus, res, res->flags, size, align, min,
+					type_mask, alignf, alignf_data);
+}
 EXPORT_SYMBOL(pci_bus_alloc_resource);
 
 /*
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index ba3c3fddddc2..8297cfb5dcd5 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -567,6 +567,12 @@ static inline int pci_resource_num(const struct pci_dev *dev,
 	return resno;
 }
 
+int __pci_bus_alloc_resource(struct pci_bus *bus, struct resource *res,
+			     unsigned long flags, resource_size_t size,
+			     resource_size_t align, resource_size_t min,
+			     unsigned long type_mask, resource_alignf alignf,
+			     void *alignf_data);
+
 void pbus_validate_busn(struct pci_bus *bus);
 struct resource *pbus_select_window(struct pci_bus *bus,
 				    const struct resource *res);
-- 
2.56.0.rc1.315.gc6ed9934b7-goog