drm/i915: Allow frame buffers up to 4096x4096 on 915/945 class hardware

The 915 and 945 scanout engines can handle frame buffers up to 4096 pixels
wide. Pre-9xx hardware has an 8192 byte stride limit, and so we leave the
existing 2048 max in place.

I'm not sure why we limit the height to the same value; there's no intrinsic
hardware limit in the scanout engine.
Signed-off-by: Keith Packard <keithp@keithp.com>
Signed-off-by: Eric Anholt <eric@anholt.net>

drivers/gpu/drm/i915/intel_display.c

@@ -3148,6 +3148,9 @@ void intel_modeset_init(struct drm_device *dev)
 	if (IS_I965G(dev)) {
 		dev->mode_config.max_width = 8192;
 		dev->mode_config.max_height = 8192;
+	} else if (IS_I9XX(dev)) {
+		dev->mode_config.max_width = 4096;
+		dev->mode_config.max_height = 4096;
 	} else {
 		dev->mode_config.max_width = 2048;
 		dev->mode_config.max_height = 2048;