drm/ast: add widescreen + rb modes from X.org driver (v2)

This syncs up the mode code from the X.org driver upstream,
and adds the mode validation step for hw that doesn't have
widescreen.

v2: (from Egbert Eich <eich@suse.de)
squash drm/ast: Use correct structure member for mode validation
to avoid bisect regression.

In struct drm_display_mode crtc_hdisplay and crtc_vdisplay are holding
the crtc parameters after mode fixup. For validation we need hdisplay and
vdisplay.

Signed-off-by: Egbert Eich <eich@suse.de>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/ast/ast_main.c b/drivers/gpu/drm/ast/ast_main.c
index 50535fd..cd0a791 100644
--- a/drivers/gpu/drm/ast/ast_main.c
+++ b/drivers/gpu/drm/ast/ast_main.c
@@ -66,6 +66,7 @@
 static int ast_detect_chip(struct drm_device *dev)
 {
 	struct ast_private *ast = dev->dev_private;
+	uint32_t data, jreg;
 
 	if (dev->pdev->device == PCI_CHIP_AST1180) {
 		ast->chip = AST1100;
@@ -104,6 +105,33 @@
 			DRM_INFO("AST 2000 detected\n");
 		}
 	}
+
+	switch (ast->chip) {
+	case AST1180:
+		ast->support_wide_screen = true;
+		break;
+	case AST2000:
+		ast->support_wide_screen = false;
+		break;
+	default:
+		jreg = ast_get_index_reg_mask(ast, AST_IO_CRTC_PORT, 0xd0, 0xff);
+		if (!(jreg & 0x80))
+			ast->support_wide_screen = true;
+		else if (jreg & 0x01)
+			ast->support_wide_screen = true;
+		else {
+			ast->support_wide_screen = false;
+			if (ast->chip == AST2300) {
+				ast_write32(ast, 0xf004, 0x1e6e0000);
+				ast_write32(ast, 0xf000, 0x1);
+				data = ast_read32(ast, 0x1207c);
+				if ((data & 0x300) == 0) /* ast1300 */
+					ast->support_wide_screen = true;
+			}
+		}
+		break;
+	}
+
 	return 0;
 }