sysfb_simplefb: adjust BOOTFB resource size to an actual PCI BAR

From: Pavel Roskin <proski@gnu.org>

This fixes a warning with stack trace when nouveau allocates iomem area
on Lenovo ThinkPad W530:

resource map sanity check conflict: 0xf0000000 0xf1ffffff 0xf1000000
0xf112bfff BOOTFB
---
 arch/x86/kernel/sysfb_simplefb.c |   37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/arch/x86/kernel/sysfb_simplefb.c b/arch/x86/kernel/sysfb_simplefb.c
index 22513e9..6c2820b 100644
--- a/arch/x86/kernel/sysfb_simplefb.c
+++ b/arch/x86/kernel/sysfb_simplefb.c
@@ -21,12 +21,47 @@
 #include <linux/mm.h>
 #include <linux/platform_data/simplefb.h>
 #include <linux/platform_device.h>
+#include <linux/pci.h>
 #include <linux/screen_info.h>
 #include <asm/sysfb.h>
 
 static const char simplefb_resname[] = "BOOTFB";
 static const struct simplefb_format formats[] = SIMPLEFB_FORMATS;
 
+#ifdef CONFIG_PCI
+/* Adjust resource to a PCI BAR of a VGA device if possible */
+static __init void adjust_pci_res(struct resource *res)
+{
+	struct pci_dev *dev = NULL;
+	int i;
+
+	for_each_pci_dev(dev) {
+		if ((dev->class >> 8) != PCI_CLASS_DISPLAY_VGA)
+			continue;
+		for (i = 0; i < DEVICE_COUNT_RESOURCE; i++) {
+			resource_size_t start, end;
+
+			if (!(pci_resource_flags(dev, i) & IORESOURCE_MEM))
+				continue;
+			start = pci_resource_start(dev, i);
+			if (start == 0)
+				continue;
+			if (res->start < start)
+				continue;
+			end = pci_resource_end(dev, i);
+			if (res->end > end)
+				continue;
+			/* Found a matching resource */
+			res->start = start;
+			res->end = end;
+			break;
+		}
+	}
+}
+#else
+#define adjust_pci_res(res)
+#endif
+
 /* try parsing x86 screen_info into a simple-framebuffer mode struct */
 __init bool parse_mode(const struct screen_info *si,
 		       struct simplefb_platform_data *mode)
@@ -86,6 +121,8 @@ __init int create_simplefb(const struct screen_info *si,
 	if (res.end <= res.start)
 		return -EINVAL;
 
+	adjust_pci_res(&res);
+
 	pd = platform_device_register_resndata(NULL, "simple-framebuffer", 0,
 					       &res, 1, mode, sizeof(*mode));
 	if (IS_ERR(pd))