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Message-ID: <5c178d7e-5022-f5e5-791d-d3800114b42b@quicinc.com>
Date: Wed, 12 Oct 2022 16:03:06 -0700
From: Abhinav Kumar <quic_abhinavk@...cinc.com>
To: Marijn Suijten <marijn.suijten@...ainline.org>,
<phone-devel@...r.kernel.org>
CC: Vinod Koul <vkoul@...nel.org>,
Jami Kettunen <jami.kettunen@...ainline.org>,
David Airlie <airlied@...il.com>,
<linux-arm-msm@...r.kernel.org>,
Vladimir Lypak <vladimir.lypak@...il.com>,
Konrad Dybcio <konrad.dybcio@...ainline.org>,
<dri-devel@...ts.freedesktop.org>,
Douglas Anderson <dianders@...omium.org>,
Rob Clark <robdclark@...il.com>,
Martin Botka <martin.botka@...ainline.org>,
<~postmarketos/upstreaming@...ts.sr.ht>,
Daniel Vetter <daniel@...ll.ch>,
AngeloGioacchino Del Regno
<angelogioacchino.delregno@...ainline.org>,
Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
<freedreno@...ts.freedesktop.org>, Sean Paul <sean@...rly.run>,
<linux-kernel@...r.kernel.org>
Subject: Re: [Freedreno] [PATCH v3 06/10] drm/msm/dsi: Migrate to
drm_dsc_compute_rc_parameters()
On 10/9/2022 11:50 AM, Marijn Suijten wrote:
> As per the FIXME this code is entirely duplicate with what is already
> provided inside drm_dsc_compute_rc_parameters(), and it is yet unknown
> why this comment was put in place instead of resolved from the get-go.
> Not only does it save on duplication, it would have also spared certain
> issues.
>
> For example, this code from downstream assumed dsc->bits_per_pixel to
> contain an integer value, whereas the upstream drm_dsc_config struct has
> it with 4 fractional bits. drm_dsc_compute_rc_parameters() already
> accounts for this feat, and the sole remaining use of
> dsc->bits_per_pixel inside dsi_populate_dsc_params() will be addressed
> in a separate patch.
>
This is a nice cleanup! Thanks for doing this. I would actually like to
move towards the drm_dsc_compute_rc_parameters() API.
But I would like to hold back this change till Vinod clarifies because
Vinod had mentioned that with drm_dsc_compute_rc_parameters() he was
seeing a mismatch in the computation of two values.
slice_bpg_offset and the final_offset.
The difference between the upstream drm_dsc_compute_rc_parameters() and
dsi_populate_dsc_params() causing this was not clear to me from his
explanation earlier.
So this was left as a to-do item.
I would like this to be re-tested on pixel3 and check if this works for
vinod. If not, i think its the right time to debug why and not delay
this more.
Thanks
Abhinav
> Fixes: b9080324d6ca ("drm/msm/dsi: add support for dsc data")
> Signed-off-by: Marijn Suijten <marijn.suijten@...ainline.org>
> ---
> drivers/gpu/drm/msm/dsi/dsi_host.c | 64 +++---------------------------
> 1 file changed, 6 insertions(+), 58 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c
> index 83cde4d62b68..68c39debc22f 100644
> --- a/drivers/gpu/drm/msm/dsi/dsi_host.c
> +++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
> @@ -21,6 +21,7 @@
>
> #include <video/mipi_display.h>
>
> +#include <drm/display/drm_dsc_helper.h>
> #include <drm/drm_of.h>
>
> #include "dsi.h"
> @@ -1771,14 +1772,6 @@ 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;
> @@ -1804,11 +1797,11 @@ 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;
> @@ -1820,52 +1813,7 @@ 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)
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