drm/kmb: Limit supported mode to 1080p

KMB only supports single resolution(1080p), this commit checks for
1920x1080x60 or 1920x1080x59 in crtc_mode_valid.
Also, modes with vfp < 4 are not supported in KMB display. This change
prunes display modes with vfp < 4.

v2: added vfp check

Fixes: 7f7b96a ("drm/kmb: Add support for KeemBay Display")
Co-developed-by: Edmund Dea <edmund.j.dea@intel.com>
Signed-off-by: Edmund Dea <edmund.j.dea@intel.com>
Signed-off-by: Anitha Chrisanthus <anitha.chrisanthus@intel.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Link:https://patchwork.freedesktop.org/patch/msgid/20211013233632.471892-2-anitha.chrisanthus@intel.com
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>

drivers/gpu/drm/kmb/kmb_crtc.c

@@ -185,11 +185,45 @@ static void kmb_crtc_atomic_flush(struct drm_crtc *crtc,
 	spin_unlock_irq(&crtc->dev->event_lock);
 }
 
+static enum drm_mode_status
+		kmb_crtc_mode_valid(struct drm_crtc *crtc,
+				    const struct drm_display_mode *mode)
+{
+	int refresh;
+	struct drm_device *dev = crtc->dev;
+	int vfp = mode->vsync_start - mode->vdisplay;
+
+	if (mode->vdisplay < KMB_CRTC_MAX_HEIGHT) {
+		drm_dbg(dev, "height = %d less than %d",
+			mode->vdisplay, KMB_CRTC_MAX_HEIGHT);
+		return MODE_BAD_VVALUE;
+	}
+	if (mode->hdisplay < KMB_CRTC_MAX_WIDTH) {
+		drm_dbg(dev, "width = %d less than %d",
+			mode->hdisplay, KMB_CRTC_MAX_WIDTH);
+		return MODE_BAD_HVALUE;
+	}
+	refresh = drm_mode_vrefresh(mode);
+	if (refresh < KMB_MIN_VREFRESH || refresh > KMB_MAX_VREFRESH) {
+		drm_dbg(dev, "refresh = %d less than %d or greater than %d",
+			refresh, KMB_MIN_VREFRESH, KMB_MAX_VREFRESH);
+		return MODE_BAD;
+	}
+
+	if (vfp < KMB_CRTC_MIN_VFP) {
+		drm_dbg(dev, "vfp = %d less than %d", vfp, KMB_CRTC_MIN_VFP);
+		return MODE_BAD;
+	}
+
+	return MODE_OK;
+}
+
 static const struct drm_crtc_helper_funcs kmb_crtc_helper_funcs = {
 	.atomic_begin = kmb_crtc_atomic_begin,
 	.atomic_enable = kmb_crtc_atomic_enable,
 	.atomic_disable = kmb_crtc_atomic_disable,
 	.atomic_flush = kmb_crtc_atomic_flush,
+	.mode_valid = kmb_crtc_mode_valid,
 };
 
 int kmb_setup_crtc(struct drm_device *drm)

drivers/gpu/drm/kmb/kmb_drv.h

@@ -20,11 +20,18 @@
 #define DRIVER_MAJOR			1
 #define DRIVER_MINOR			1
 
+/* Platform definitions */
+#define KMB_CRTC_MIN_VFP		4
+#define KMB_CRTC_MAX_WIDTH		1920 /* max width in pixels */
+#define KMB_CRTC_MAX_HEIGHT		1080 /* max height in pixels */
+#define KMB_CRTC_MIN_WIDTH		1920
+#define KMB_CRTC_MIN_HEIGHT		1080
 #define KMB_FB_MAX_WIDTH		1920
 #define KMB_FB_MAX_HEIGHT		1080
 #define KMB_FB_MIN_WIDTH		1
 #define KMB_FB_MIN_HEIGHT		1
-
+#define KMB_MIN_VREFRESH		59    /*vertical refresh in Hz */
+#define KMB_MAX_VREFRESH		60    /*vertical refresh in Hz */
 #define KMB_LCD_DEFAULT_CLK		200000000
 #define KMB_SYS_CLK_MHZ			500