[PATCH v4 4/5] PCI: Add a new option for resource_alignment to reassign alignment

[Yongji Xie]

When using resource_alignment kernel parameter, the current
implement reassigns the alignment by changing resources' size
which can potentially break some drivers. For example, the driver
uses the size to locate some register whose length is related
to the size.

This patch adds a new option "noresize" for the parameter to
solve this problem.

Signed-off-by: Yongji Xie <xyjxie at linux.vnet.ibm.com>
---
 Documentation/kernel-parameters.txt |    9 ++++++---
 drivers/pci/pci.c                   |   37 +++++++++++++++++++++++++----------
 2 files changed, 33 insertions(+), 13 deletions(-)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 46c030a..c64e439 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -3023,15 +3023,18 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 				window. The default value is 64 megabytes.
 		resource_alignment=
 				Format:
-				[<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
-				[<order of align>@]pci:<vendor>:<device>\
-						[:<subvendor>:<subdevice>][; ...]
+				[<order of align>@][noresize@][<domain>:]
+				<bus>:<slot>.<func>[; ...]
+				[<order of align>@][noresize@]pci:<vendor>:<device>
+				[:<subvendor>:<subdevice>][; ...]
 				Specifies alignment and device to reassign
 				aligned memory resources.
 				If <order of align> is not specified,
 				PAGE_SIZE is used as alignment.
 				PCI-PCI bridge can be specified, if resource
 				windows need to be expanded.
+				noresize: Don't change the resources' sizes when
+				reassigning alignment.
 		ecrc=		Enable/disable PCIe ECRC (transaction layer
 				end-to-end CRC checking).
 				bios: Use BIOS/firmware settings. This is the
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index caa0894..d895be7 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -4946,11 +4946,13 @@ static DEFINE_SPINLOCK(resource_alignment_lock);
 /**
  * pci_specified_resource_alignment - get resource alignment specified by user.
  * @dev: the PCI device to get
+ * @resize: whether or not to change resources' size when reassigning alignment
  *
  * RETURNS: Resource alignment if it is specified.
  *          Zero if it is not specified.
  */
-static resource_size_t pci_specified_resource_alignment(struct pci_dev *dev)
+static resource_size_t pci_specified_resource_alignment(struct pci_dev *dev,
+		bool *resize)
 {
 	int seg, bus, slot, func, align_order, count;
 	unsigned short vendor, device, subsystem_vendor, subsystem_device;
@@ -4974,6 +4976,13 @@ static resource_size_t pci_specified_resource_alignment(struct pci_dev *dev)
 		} else {
 			align_order = -1;
 		}
+
+		if (!strncmp(p, "noresize@", 9)) {
+			*resize = false;
+			p += 9;
+		} else
+			*resize = true;
+
 		if (strncmp(p, "pci:", 4) == 0) {
 			/* PCI vendor/device (subvendor/subdevice) ids are specified */
 			p += 4;
@@ -5045,6 +5054,7 @@ void pci_reassigndev_resource_alignment(struct pci_dev *dev)
 {
 	int i;
 	struct resource *r;
+	bool resize = true;
 	resource_size_t align, size;
 
 	/*
@@ -5057,7 +5067,7 @@ void pci_reassigndev_resource_alignment(struct pci_dev *dev)
 		return;
 
 	/* check if specified PCI is target device to reassign */
-	align = pci_specified_resource_alignment(dev);
+	align = pci_specified_resource_alignment(dev, &resize);
 	if (!align)
 		return;
 
@@ -5080,15 +5090,22 @@ void pci_reassigndev_resource_alignment(struct pci_dev *dev)
 		}
 
 		size = resource_size(r);
-		if (size < align) {
-			size = align;
-			dev_info(&dev->dev,
-				"Rounding up size of resource #%d to %#llx.\n",
-				i, (unsigned long long)size);
+		if (resize) {
+			if (size < align) {
+				size = align;
+				dev_info(&dev->dev,
+					"Rounding up size of resource #%d to %#llx.\n",
+					i, (unsigned long long)size);
+			}
+			r->flags |= IORESOURCE_UNSET;
+			r->end = size - 1;
+			r->start = 0;
+		} else {
+			r->flags &= ~IORESOURCE_SIZEALIGN;
+			r->flags |= IORESOURCE_STARTALIGN | IORESOURCE_UNSET;
+			r->start = max(align, size);
+			r->end = r->start + size - 1;
 		}
-		r->flags |= IORESOURCE_UNSET;
-		r->end = size - 1;
-		r->start = 0;
 	}
 	/* Need to disable bridge's resource window,
 	 * to enable the kernel to reassign new resource
-- 
1.7.9.5