OMAPDSS: DISPC: decimation rounding fix

The driver uses DIV_ROUND_UP when calculating decimated width & height.
For example, when decimating with 3, the width is calculated as:

  width = DIV_ROUND_UP(width, decim_x);

This yields bad results for some values. For example, 800/3=266.666...,
which is rounded to 267. When the input width is set to 267, and pixel
increment is set to 3, this causes the dispc to read a line of 801
pixels, i.e. it reads a wrong pixel at the end of the line.

Even more pressing, the above rounding causes a BUG() in pixinc(), as
the value of 801 is used to calculate row increment, leading to a bad
value being passed to pixinc().

This patch fixes the decimation by removing the DIV_ROUND_UP()s when
calculating width and height for decimation.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>

diff --git a/drivers/video/omap2/dss/dispc.c b/drivers/video/omap2/dss/dispc.c
index bbeb8dd..77d6221 100644 (file)
--- a/drivers/video/omap2/dss/dispc.c
+++ b/drivers/video/omap2/dss/dispc.c
@@ -2160,8 +2160,8 @@ static int dispc_ovl_calc_scaling_24xx(unsigned long pclk, unsigned long lclk,
        *five_taps = false;
 
        do {
-               in_height = DIV_ROUND_UP(height, *decim_y);
-               in_width = DIV_ROUND_UP(width, *decim_x);
+               in_height = height / *decim_y;
+               in_width = width / *decim_x;
                *core_clk = dispc.feat->calc_core_clk(pclk, in_width,
                                in_height, out_width, out_height, mem_to_mem);
                error = (in_width > maxsinglelinewidth || !*core_clk ||
@@ -2199,8 +2199,8 @@ static int dispc_ovl_calc_scaling_34xx(unsigned long pclk, unsigned long lclk,
                        dss_feat_get_param_max(FEAT_PARAM_LINEWIDTH);
 
        do {
-               in_height = DIV_ROUND_UP(height, *decim_y);
-               in_width = DIV_ROUND_UP(width, *decim_x);
+               in_height = height / *decim_y;
+               in_width = width / *decim_x;
                *five_taps = in_height > out_height;
 
                if (in_width > maxsinglelinewidth)
@@ -2268,7 +2268,7 @@ static int dispc_ovl_calc_scaling_44xx(unsigned long pclk, unsigned long lclk,
 {
        u16 in_width, in_width_max;
        int decim_x_min = *decim_x;
-       u16 in_height = DIV_ROUND_UP(height, *decim_y);
+       u16 in_height = height / *decim_y;
        const int maxsinglelinewidth =
                                dss_feat_get_param_max(FEAT_PARAM_LINEWIDTH);
        const int maxdownscale = dss_feat_get_param_max(FEAT_PARAM_DOWNSCALE);
@@ -2287,7 +2287,7 @@ static int dispc_ovl_calc_scaling_44xx(unsigned long pclk, unsigned long lclk,
                return -EINVAL;
 
        do {
-               in_width = DIV_ROUND_UP(width, *decim_x);
+               in_width = width / *decim_x;
        } while (*decim_x <= *x_predecim &&
                        in_width > maxsinglelinewidth && ++*decim_x);
 
@@ -2466,8 +2466,8 @@ static int dispc_ovl_setup_common(enum omap_plane plane,
        if (r)
                return r;
 
-       in_width = DIV_ROUND_UP(in_width, x_predecim);
-       in_height = DIV_ROUND_UP(in_height, y_predecim);
+       in_width = in_width / x_predecim;
+       in_height = in_height / y_predecim;
 
        if (color_mode == OMAP_DSS_COLOR_YUV2 ||
                        color_mode == OMAP_DSS_COLOR_UYVY ||