Commit 01a90798 authored by Marijn Suijten's avatar Marijn Suijten Committed by Dmitry Baryshkov
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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: b9080324 ("drm/msm/dsi: add support for dsc data")
Reviewed-by: default avatarAbhinav Kumar <quic_abhinavk@quicinc.com>
Reviewed-by: default avatarDmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: default avatarMarijn 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: default avatarDmitry Baryshkov <dmitry.baryshkov@linaro.org>
parent 572e9fd6

drivers/gpu/drm/msm/dsi/dsi_host.c

+1 −9
Original line number Diff line number Diff line
@@ -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;