Commit c3a1aabc authored by Marijn Suijten's avatar Marijn Suijten Committed by Dmitry Baryshkov
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drm/msm/dsi: Migrate to drm_dsc_compute_rc_parameters() 

As per the FIXME this code is entirely duplicate with what is already
provided inside drm_dsc_compute_rc_parameters(), supposedly because that
function was yielding "incorrect" results while in reality the panel
driver(s?) used for testing were providing incorrect parameters.

For example, this code from downstream assumed dsc->bits_per_pixel to
contain an integer value, whereas the upstream drm_dsc_config struct
stores it with 4 fractional bits.  drm_dsc_compute_rc_parameters()
already accounts for this feat while the panel driver used for testing
[1] wasn't, hence making drm_dsc_compute_rc_parameters() seem like it
was returning an incorrect result.
Other users of dsc->bits_per_pixel inside dsi_populate_dsc_params() also
treat it in the same erroneous way, and will be addressed in a separate
patch.
In the end, using drm_dsc_compute_rc_parameters() spares both a lot of
duplicate code and erratic behaviour.

[1]: https://git.linaro.org/people/vinod.koul/kernel.git/commit/?h=topic/pixel3_5.18-rc1&id=1d7d98ad564f1ec69e7525e07418918d90f247a1



Fixes: b9080324 ("drm/msm/dsi: add support for dsc data")
Reviewed-by: default avatarAbhinav Kumar <quic_abhinavk@quicinc.com>
Signed-off-by: default avatarMarijn Suijten <marijn.suijten@somainline.org>
Reviewed-by: default avatarDmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/508939/
Link: https://lore.kernel.org/r/20221026182824.876933-7-marijn.suijten@somainline.org


Signed-off-by: default avatarDmitry Baryshkov <dmitry.baryshkov@linaro.org>
parent 0ca870ca

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

+6 −58
Original line number Diff line number Diff line
@@ -21,6 +21,7 @@ 


#include <video/mipi_display.h>



#include <drm/display/drm_dsc_helper.h>

#include <drm/drm_of.h>



#include "dsi.h"
@@ -1749,14 +1750,6 @@ static char bpg_offset[DSC_NUM_BUF_RANGES] = { 


static int dsi_populate_dsc_params(struct drm_dsc_config *dsc)

{

	int mux_words_size;

	int groups_per_line, groups_total;

	int min_rate_buffer_size;

	int hrd_delay;

	int pre_num_extra_mux_bits, num_extra_mux_bits;

	int slice_bits;

	int data;

	int final_value, final_scale;

	int i;



	dsc->rc_model_size = 8192;
@@ -1782,11 +1775,11 @@ static int dsi_populate_dsc_params(struct drm_dsc_config *dsc) 
	if (dsc->bits_per_pixel != 8)

		dsc->initial_offset = 2048;	/* bpp = 12 */



	mux_words_size = 48;		/* bpc == 8/10 */

	if (dsc->bits_per_component == 12)

		mux_words_size = 64;

	if (dsc->bits_per_component <= 10)

		dsc->mux_word_size = DSC_MUX_WORD_SIZE_8_10_BPC;

	else

		dsc->mux_word_size = DSC_MUX_WORD_SIZE_12_BPC;



	dsc->mux_word_size = mux_words_size;

	dsc->initial_xmit_delay = 512;

	dsc->initial_scale_value = 32;

	dsc->first_line_bpg_offset = 12;
@@ -1798,52 +1791,7 @@ static int dsi_populate_dsc_params(struct drm_dsc_config *dsc) 
	dsc->rc_quant_incr_limit0 = 11;

	dsc->rc_quant_incr_limit1 = 11;



	/* FIXME: need to call drm_dsc_compute_rc_parameters() so that rest of

	 * params are calculated

	 */

	groups_per_line = DIV_ROUND_UP(dsc->slice_width, 3);

	dsc->slice_chunk_size = DIV_ROUND_UP(dsc->slice_width * dsc->bits_per_pixel, 8);



	/* rbs-min */

	min_rate_buffer_size =  dsc->rc_model_size - dsc->initial_offset +

				dsc->initial_xmit_delay * dsc->bits_per_pixel +

				groups_per_line * dsc->first_line_bpg_offset;



	hrd_delay = DIV_ROUND_UP(min_rate_buffer_size, dsc->bits_per_pixel);



	dsc->initial_dec_delay = hrd_delay - dsc->initial_xmit_delay;



	dsc->initial_scale_value = 8 * dsc->rc_model_size /

				       (dsc->rc_model_size - dsc->initial_offset);



	slice_bits = 8 * dsc->slice_chunk_size * dsc->slice_height;



	groups_total = groups_per_line * dsc->slice_height;



	data = dsc->first_line_bpg_offset * 2048;



	dsc->nfl_bpg_offset = DIV_ROUND_UP(data, (dsc->slice_height - 1));



	pre_num_extra_mux_bits = 3 * (mux_words_size + (4 * dsc->bits_per_component + 4) - 2);



	num_extra_mux_bits = pre_num_extra_mux_bits - (mux_words_size -

			     ((slice_bits - pre_num_extra_mux_bits) % mux_words_size));



	data = 2048 * (dsc->rc_model_size - dsc->initial_offset + num_extra_mux_bits);

	dsc->slice_bpg_offset = DIV_ROUND_UP(data, groups_total);



	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;



	final_scale = 8 * dsc->rc_model_size / (dsc->rc_model_size - final_value);



	data = (final_scale - 9) * (dsc->nfl_bpg_offset + dsc->slice_bpg_offset);

	dsc->scale_increment_interval = (2048 * dsc->final_offset) / data;



	dsc->scale_decrement_interval = groups_per_line / (dsc->initial_scale_value - 8);



	return 0;

	return drm_dsc_compute_rc_parameters(dsc);

}



static int dsi_host_parse_dt(struct msm_dsi_host *msm_host)