drm/radeon/kms: add support for "Surround View"

"Surround View" is an option in the system bios that
enables the AMD IGP chip in conjunction with a
discrete AMD card.  However, since the IGP vbios is
part of the system bios it is not accessible via the
rom bar or the legacy vga location.  When "Surround View"
is enabled in the system bios, the system bios puts a
copy of the IGP vbios image at the start of vram.

This patch adds support for reading the vbios image out
of vram on IGP cards.

Signed-off-by: Alex Deucher <alexdeucher@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/radeon/radeon_bios.c

@@ -33,12 +33,50 @@
 /*
  * BIOS.
  */
+
+/* If you boot an IGP board with a discrete card as the primary,
+ * the IGP rom is not accessible via the rom bar as the IGP rom is
+ * part of the system bios.  On boot, the system bios puts a
+ * copy of the igp rom at the start of vram if a discrete card is
+ * present.
+ */
+static bool igp_read_bios_from_vram(struct radeon_device *rdev)
+{
+	uint8_t __iomem *bios;
+	resource_size_t vram_base;
+	resource_size_t size = 256 * 1024; /* ??? */
+
+	rdev->bios = NULL;
+	vram_base = drm_get_resource_start(rdev->ddev, 0);
+	bios = ioremap(vram_base, size);
+	if (!bios) {
+		DRM_ERROR("Unable to mmap vram\n");
+		return false;
+	}
+
+	if (size == 0 || bios[0] != 0x55 || bios[1] != 0xaa) {
+		iounmap(bios);
+		DRM_ERROR("bad rom signature\n");
+		return false;
+	}
+	rdev->bios = kmalloc(size, GFP_KERNEL);
+	if (rdev->bios == NULL) {
+		iounmap(bios);
+		DRM_ERROR("kmalloc failed\n");
+		return false;
+	}
+	memcpy(rdev->bios, bios, size);
+	iounmap(bios);
+	return true;
+}
+
 static bool radeon_read_bios(struct radeon_device *rdev)
 {
 	uint8_t __iomem *bios;
 	size_t size;
 
 	rdev->bios = NULL;
+	/* XXX: some cards may return 0 for rom size? ddx has a workaround */
 	bios = pci_map_rom(rdev->pdev, &size);
 	if (!bios) {
 		return false;
@@ -341,7 +379,9 @@ static bool legacy_read_disabled_bios(struct radeon_device *rdev)
 
 static bool radeon_read_disabled_bios(struct radeon_device *rdev)
 {
-	if (rdev->family >= CHIP_RV770)
+	if (rdev->flags & RADEON_IS_IGP)
+		return igp_read_bios_from_vram(rdev);
+	else if (rdev->family >= CHIP_RV770)
 		return r700_read_disabled_bios(rdev);
 	else if (rdev->family >= CHIP_R600)
 		return r600_read_disabled_bios(rdev);
@@ -356,7 +396,12 @@ bool radeon_get_bios(struct radeon_device *rdev)
 	bool r;
 	uint16_t tmp;
 
-	r = radeon_read_bios(rdev);
+	if (rdev->flags & RADEON_IS_IGP) {
+		r = igp_read_bios_from_vram(rdev);
+		if (r == false)
+			r = radeon_read_bios(rdev);
+	} else
+		r = radeon_read_bios(rdev);
 	if (r == false) {
 		r = radeon_read_disabled_bios(rdev);
 	}