exynos: replace G2D_DOUBLE_TO_FIXED macro with function

This also avoids the floating point conversion steps and just
uses pure integer arithmetic.
Since the G2D hardware scaling approach is a bit unintuitive,
document it in the function as well.

v2: Explicitly mention the normalization constant.
v3: Use common commenting style as pointed out by
    Emil Velikov <emil.l.velikov@gmail.com>.

Signed-off-by: Tobias Jakobi <tjakobi@math.uni-bielefeld.de>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Tested-by: Joonyoung Shim <jy0922.shim@samsung.com>

diff --git a/exynos/exynos_fimg2d.c b/exynos/exynos_fimg2d.c
index ce1ba1e..9c66c3a 100644 (file)
--- a/exynos/exynos_fimg2d.c
+++ b/exynos/exynos_fimg2d.c
@@ -41,6 +41,18 @@
 
 #define MIN(a, b)      ((a) < (b) ? (a) : (b))
 
+static unsigned int g2d_get_scaling(unsigned int src, unsigned int dst)
+{
+       /*
+        * The G2D hw scaling factor is a normalized inverse of the scaling factor.
+        * For example: When source width is 100 and destination width is 200
+        * (scaling of 2x), then the hw factor is NC * 100 / 200.
+        * The normalization factor (NC) is 2^16 = 0x10000.
+        */
+
+       return ((src << 16) / dst);
+}
+
 static unsigned int g2d_get_blend_op(enum e_g2d_op op)
 {
        union g2d_blend_func_val val;
@@ -428,7 +440,7 @@ g2d_copy_with_scale(struct g2d_context *ctx, struct g2d_image *src,
        union g2d_rop4_val rop4;
        union g2d_point_val pt;
        unsigned int scale;
-       double scale_x = 0.0f, scale_y = 0.0f;
+       unsigned int scale_x, scale_y;
 
        g2d_add_cmd(ctx, DST_SELECT_REG, G2D_SELECT_MODE_BGCOLOR);
        g2d_add_cmd(ctx, DST_COLOR_MODE_REG, dst->color_mode);
@@ -454,8 +466,8 @@ g2d_copy_with_scale(struct g2d_context *ctx, struct g2d_image *src,
                scale = 0;
        else {
                scale = 1;
-               scale_x = (double)src_w / (double)dst_w;
-               scale_y = (double)src_h / (double)dst_h;
+               scale_x = g2d_get_scaling(src_w, dst_w);
+               scale_y = g2d_get_scaling(src_h, dst_h);
        }
 
        if (src_x + src_w > src->width)
@@ -487,8 +499,8 @@ g2d_copy_with_scale(struct g2d_context *ctx, struct g2d_image *src,
 
        if (scale) {
                g2d_add_cmd(ctx, SRC_SCALE_CTRL_REG, G2D_SCALE_MODE_BILINEAR);
-               g2d_add_cmd(ctx, SRC_XSCALE_REG, G2D_DOUBLE_TO_FIXED(scale_x));
-               g2d_add_cmd(ctx, SRC_YSCALE_REG, G2D_DOUBLE_TO_FIXED(scale_y));
+               g2d_add_cmd(ctx, SRC_XSCALE_REG, scale_x);
+               g2d_add_cmd(ctx, SRC_YSCALE_REG, scale_y);
        }
 
        pt.val = 0;

diff --git a/exynos/fimg2d.h b/exynos/fimg2d.h
index 4785e2f..8e0321c 100644 (file)
--- a/exynos/fimg2d.h
+++ b/exynos/fimg2d.h
@@ -25,8 +25,6 @@
 #define G2D_MAX_CMD_LIST_NR    64
 #define G2D_PLANE_MAX_NR       2
 
-#define G2D_DOUBLE_TO_FIXED(d)         ((unsigned int)((d) * 65536.0))
-
 enum e_g2d_color_mode {
        /* COLOR FORMAT */
        G2D_COLOR_FMT_XRGB8888,