drm/exynos: fix to calculate CRTC shown via screen

This patch is to exactly calculate CRTC shown via screen for all cases.
Refer exynos_plane_get_size() function for this. Also source position of
fb is fixed when start position of CRTC is negative number.

Signed-off-by: Joonyoung Shim <jy0922.shim@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>

1 files changed, 54 insertions, 2 deletions

diff --git a/drivers/gpu/drm/exynos/exynos_drm_plane.c b/drivers/gpu/drm/exynos/exynos_drm_plane.c
index 8c3036dd512b..2a27b5678893 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_plane.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_plane.c
@@ -32,6 +32,42 @@ static const uint32_t formats[] = {
         DRM_FORMAT_NV12MT,
 };
 
+/*
+ * This function is to get X or Y size shown via screen. This needs length and
+ * start position of CRTC.
+ *
+ *      <--- length --->
+ * CRTC ----------------
+ *      ^ start        ^ end
+ *
+ * There are six cases from a to b.
+ *
+ *             <----- SCREEN ----->
+ *             0                 last
+ *   ----------|------------------|----------
+ * CRTCs
+ * a -------
+ *        b -------
+ *        c --------------------------
+ *                 d --------
+ *                           e -------
+ *                                  f -------
+ */
+static int exynos_plane_get_size(int start, unsigned length, unsigned last)
+{
+        int end = start + length;
+        int size = 0;
+
+        if (start <= 0) {
+                if (end > 0)
+                        size = min_t(unsigned, end, last);
+        } else if (start <= last) {
+                size = min_t(unsigned, last - start, length);
+        }
+
+        return size;
+}
+
 int exynos_plane_mode_set(struct drm_plane *plane, struct drm_crtc *crtc,
                           struct drm_framebuffer *fb, int crtc_x, int crtc_y,
                           unsigned int crtc_w, unsigned int crtc_h,
@@ -64,8 +100,24 @@ int exynos_plane_mode_set(struct drm_plane *plane, struct drm_crtc *crtc,
                                 (unsigned long)overlay->dma_addr[i]);
         }
 
-        actual_w = min((unsigned)(crtc->mode.hdisplay - crtc_x), crtc_w);
-        actual_h = min((unsigned)(crtc->mode.vdisplay - crtc_y), crtc_h);
+        actual_w = exynos_plane_get_size(crtc_x, crtc_w, crtc->mode.hdisplay);
+        actual_h = exynos_plane_get_size(crtc_y, crtc_h, crtc->mode.vdisplay);
+
+        if (crtc_x < 0) {
+                if (actual_w)
+                        src_x -= crtc_x;
+                else
+                        src_x += crtc_w;
+                crtc_x = 0;
+        }
+
+        if (crtc_y < 0) {
+                if (actual_h)
+                        src_y -= crtc_y;
+                else
+                        src_y += crtc_h;
+                crtc_y = 0;
+        }
 
         /* set drm framebuffer data. */
         overlay->fb_x = src_x;