bochs: add endian switching support

Recently (qemu 2.2+) the qemu stdvga got a register to switch the vga
framebuffer endianness.  This patch adds code to explicitly set the
endianness of the framebuffer.  In most cases this has no effect as
the default is guest architecture endianness.  It is needed though in
case a architecture supports both big and little endian, i.e. for
ppc64le.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/bochs/bochs_hw.c

@@ -51,7 +51,7 @@ int bochs_hw_init(struct drm_device *dev, uint32_t flags)
 {
 	struct bochs_device *bochs = dev->dev_private;
 	struct pci_dev *pdev = dev->pdev;
-	unsigned long addr, size, mem, ioaddr, iosize;
+	unsigned long addr, size, mem, ioaddr, iosize, qext_size;
 	u16 id;
 
 	if (pdev->resource[2].flags & IORESOURCE_MEM) {
@@ -115,6 +115,24 @@ int bochs_hw_init(struct drm_device *dev, uint32_t flags)
 		 size / 1024, addr,
 		 bochs->ioports ? "ioports" : "mmio",
 		 ioaddr);
+
+	if (bochs->mmio && pdev->revision >= 2) {
+		qext_size = readl(bochs->mmio + 0x600);
+		if (qext_size < 4 || qext_size > iosize)
+			goto noext;
+		DRM_DEBUG("Found qemu ext regs, size %ld\n", qext_size);
+		if (qext_size >= 8) {
+#ifdef __BIG_ENDIAN
+			writel(0xbebebebe, bochs->mmio + 0x604);
+#else
+			writel(0x1e1e1e1e, bochs->mmio + 0x604);
+#endif
+			DRM_DEBUG("  qext endian: 0x%x\n",
+				  readl(bochs->mmio + 0x604));
+		}
+	}
+
+noext:
 	return 0;
 }