drm/msm/dsi: Remove useless math in DSC calculations

Multiplying a value by 2 and adding 1 to it always results in a value
that is uneven, and that 1 gets truncated immediately when performing
integer division by 2 again.  There is no "rounding" possible here.

After that target_bpp_x16 is used to store a multiplication of
bits_per_pixel by 16 which is only ever read to immediately be divided
by 16 again, and is elided in much the same way.

Fixes: b9080324d6ca ("drm/msm/dsi: add support for dsc data")
Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Marijn Suijten <marijn.suijten@somainline.org>
Patchwork: https://patchwork.freedesktop.org/patch/508932/
Link: https://lore.kernel.org/r/20221026182824.876933-2-marijn.suijten@somainline.org
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c
index 7fbf391..8026fe6 100644 (file)
--- a/drivers/gpu/drm/msm/dsi/dsi_host.c
+++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
@@ -1762,7 +1762,6 @@ static int dsi_populate_dsc_params(struct drm_dsc_config *dsc)
        int hrd_delay;
        int pre_num_extra_mux_bits, num_extra_mux_bits;
        int slice_bits;
-       int target_bpp_x16;
        int data;
        int final_value, final_scale;
        int i;
@@ -1842,14 +1841,7 @@ static int dsi_populate_dsc_params(struct drm_dsc_config *dsc)
        data = 2048 * (dsc->rc_model_size - dsc->initial_offset + num_extra_mux_bits);
        dsc->slice_bpg_offset = DIV_ROUND_UP(data, groups_total);
 
-       /* bpp * 16 + 0.5 */
-       data = dsc->bits_per_pixel * 16;
-       data *= 2;
-       data++;
-       data /= 2;
-       target_bpp_x16 = data;
-
-       data = (dsc->initial_xmit_delay * target_bpp_x16) / 16;
+       data = dsc->initial_xmit_delay * dsc->bits_per_pixel;
        final_value =  dsc->rc_model_size - data + num_extra_mux_bits;
        dsc->final_offset = final_value;