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Message-Id: <D77VIRU2Z0L9.20OBL2OMAIA7I@fairphone.com>
Date: Tue, 21 Jan 2025 16:58:24 +0100
From: "Luca Weiss" <luca.weiss@...rphone.com>
To: "Marijn Suijten" <marijn.suijten@...ainline.org>, "Rob Clark"
<robdclark@...il.com>, "Abhinav Kumar" <quic_abhinavk@...cinc.com>, "Dmitry
Baryshkov" <dmitry.baryshkov@...aro.org>, "Sean Paul" <sean@...rly.run>,
"David Airlie" <airlied@...il.com>, "Simona Vetter" <simona@...ll.ch>
Cc: <~postmarketos/upstreaming@...ts.sr.ht>, "AngeloGioacchino Del Regno"
<angelogioacchino.delregno@...labora.com>, "Konrad Dybcio"
<konrad.dybcio@....qualcomm.com>, "Martin Botka"
<martin.botka@...ainline.org>, "Jami Kettunen"
<jami.kettunen@...ainline.org>, <linux-arm-msm@...r.kernel.org>,
<dri-devel@...ts.freedesktop.org>, <freedreno@...ts.freedesktop.org>,
<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC] drm/msm/dpu: Fall back to a single DSC encoder
(1:1:1) on small SoCs
Hi Marijn,
On Tue Jan 21, 2025 at 12:06 AM CET, Marijn Suijten wrote:
> Some SoCs such as SC7280 (used in the FairPhone 5) have only a single
> DSC "hard slice" encoder. The current hardcoded use of 2:2:1 topology
> (2 LM and 2 DSC for a single interface) make it impossible to use
> Display Stream Compression panels with mainline, which is exactly what's
> installed on the FairPhone 5.
Nitpick, if you send another revision: s/FairPhone/Fairphone/
>
> By loosening the hardcoded `num_dsc = 2` to fall back to `num_dsc =
> 1` when the catalog only contains one entry, we can trivially support
> this phone and unblock further panel enablement on mainline. A few
> more supporting changes in this patch ensure hardcoded constants of 2
> DSC encoders are replaced to count or read back the actual number of
> DSC hardware blocks that are enabled for the given virtual encoder.
> Likewise DSC_MODE_SPLIT_PANEL can no longer be unconditionally enabled.
This unblocks panel enablement on upstream without any hacks on top.
Many thanks!
Tested-by: Luca Weiss <luca.weiss@...rphone.com>
> Cc: Luca Weiss <luca.weiss@...rphone.com>
> Signed-off-by: Marijn Suijten <marijn.suijten@...ainline.org>
> ---
> Note that this doesn't paint the full picture in case there are SoCs
> with more DSC hardware blocks, but when multiple virtual encoders
> have already allocated most of them. My initial plan was to code
> ahead for dynamically tracking and reallocating these blocks in RM, if
> some virtual encoder could potentially be using too many DSC encoders
> which, while "power optimal", may not be able to support the number of
> requested displays/interfaces. Such a solution would automatically
> ensure DSCmerge is *not* used when there are not enough hardware blocks
> available in the first place.
> ---
> drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c | 47 +++++++++++++++--------------
> 1 file changed, 25 insertions(+), 22 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> index 5172ab4dea995a154cd88d05c3842d7425fc34ce..dcf17b5e8ac8eb76f5ba038fcce48e47f32299d5 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> @@ -622,9 +622,10 @@ bool dpu_encoder_use_dsc_merge(struct drm_encoder *drm_enc)
> if (dpu_enc->phys_encs[i])
> intf_count++;
>
> - /* See dpu_encoder_get_topology, we only support 2:2:1 topology */
> if (dpu_enc->dsc)
> - num_dsc = 2;
> + for (i = 0; i < MAX_CHANNELS_PER_ENC; i++)
> + if (dpu_enc->hw_dsc[i])
> + num_dsc++;
>
> return (num_dsc > 0) && (num_dsc > intf_count);
> }
> @@ -664,7 +665,7 @@ static struct msm_display_topology dpu_encoder_get_topology(
> /* Datapath topology selection
> *
> * Dual display
> - * 2 LM, 2 INTF ( Split display using 2 interfaces)
> + * 2 LM, 2 INTF (split display using 2 interfaces)
> *
> * Single display
> * 1 LM, 1 INTF
> @@ -686,13 +687,19 @@ static struct msm_display_topology dpu_encoder_get_topology(
>
> if (dsc) {
> /*
> - * In case of Display Stream Compression (DSC), we would use
> - * 2 DSC encoders, 2 layer mixers and 1 interface
> - * this is power optimal and can drive up to (including) 4k
> - * screens
> + * Use 2 DSC encoders and 2 layer mixers per single interface
> + * when Display Stream Compression (DSC) is enabled,
> + * and when enough DSC blocks are available.
> + * This is power-optimal and can drive up to (including) 4k
> + * screens.
> */
> - topology.num_dsc = 2;
> - topology.num_lm = 2;
> + if (dpu_kms->catalog->dsc_count >= 2) {
> + topology.num_dsc = 2;
> + topology.num_lm = 2;
> + } else {
> + topology.num_dsc = 1;
> + topology.num_lm = 1;
> + }
> topology.num_intf = 1;
> }
>
> @@ -2020,32 +2027,32 @@ static void dpu_encoder_dsc_pipe_cfg(struct dpu_hw_ctl *ctl,
> static void dpu_encoder_prep_dsc(struct dpu_encoder_virt *dpu_enc,
> struct drm_dsc_config *dsc)
> {
> - /* coding only for 2LM, 2enc, 1 dsc config */
> struct dpu_encoder_phys *enc_master = dpu_enc->cur_master;
> struct dpu_hw_ctl *ctl = enc_master->hw_ctl;
> struct dpu_hw_dsc *hw_dsc[MAX_CHANNELS_PER_ENC];
> struct dpu_hw_pingpong *hw_pp[MAX_CHANNELS_PER_ENC];
> int this_frame_slices;
> int intf_ip_w, enc_ip_w;
> - int dsc_common_mode;
> + int dsc_common_mode = 0;
> int pic_width;
> u32 initial_lines;
> + int num_dsc = 0;
> int i;
>
> for (i = 0; i < MAX_CHANNELS_PER_ENC; i++) {
> hw_pp[i] = dpu_enc->hw_pp[i];
> hw_dsc[i] = dpu_enc->hw_dsc[i];
>
> - if (!hw_pp[i] || !hw_dsc[i]) {
> - DPU_ERROR_ENC(dpu_enc, "invalid params for DSC\n");
> - return;
> - }
> + if (!hw_pp[i] || !hw_dsc[i])
> + break;
> + num_dsc++;
> }
>
> dsc_common_mode = 0;
> pic_width = dsc->pic_width;
>
> - dsc_common_mode = DSC_MODE_SPLIT_PANEL;
> + if (num_dsc > 1)
> + dsc_common_mode |= DSC_MODE_SPLIT_PANEL;
> if (dpu_encoder_use_dsc_merge(enc_master->parent))
> dsc_common_mode |= DSC_MODE_MULTIPLEX;
> if (enc_master->intf_mode == INTF_MODE_VIDEO)
> @@ -2054,14 +2061,10 @@ static void dpu_encoder_prep_dsc(struct dpu_encoder_virt *dpu_enc,
> this_frame_slices = pic_width / dsc->slice_width;
> intf_ip_w = this_frame_slices * dsc->slice_width;
>
> - /*
> - * dsc merge case: when using 2 encoders for the same stream,
> - * no. of slices need to be same on both the encoders.
> - */
> - enc_ip_w = intf_ip_w / 2;
> + enc_ip_w = intf_ip_w / num_dsc;
> initial_lines = dpu_encoder_dsc_initial_line_calc(dsc, enc_ip_w);
>
> - for (i = 0; i < MAX_CHANNELS_PER_ENC; i++)
> + for (i = 0; i < num_dsc; i++)
> dpu_encoder_dsc_pipe_cfg(ctl, hw_dsc[i], hw_pp[i],
> dsc, dsc_common_mode, initial_lines);
> }
>
> ---
> base-commit: 1573c8d4cb206a2d1454ff711e79f8df2353290b
> change-id: 20240204-dpu-111-topology-b12c1de82c8a
>
> Best regards,
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