Re: [PATCH v21] drm/msm/dpu: Enable quad-pipe for DSC and dual-DSI case

From: Dmitry Baryshkov

Date: Fri Oct 02 2026 - 16:27:35 EST


On Mon, Jul 27, 2026 at 05:33:26PM +0800, Jun Nie wrote:
> To support high-resolution cases that exceed the width constrain
> or scenarios that surpass the maximum MDP clock rate, additional
> pipes are necessary to enable parallel data processing within
> the width constraints and MDP clock rate.
>
> Expand pipe array size to 4. Request 4 mixers and 4 DSCs for
> high-resolution cases where dual interfaces are enabled for virtual
> plane case. More use cases can be incorporated later if quad-pipe
> capabilities are required.
>
> Signed-off-by: Jun Nie <jun.nie@xxxxxxxxxx>
> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
> Reviewed-by: Jessica Zhang <quic_jesszhan@xxxxxxxxxxx>
> Patchwork: https://patchwork.freedesktop.org/patch/675418/
> Link: https://lore.kernel.org/r/20250918-v6-16-rc2-quad-pipe-upstream-4-v16-10-ff6232e3472f@xxxxxxxxxx
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxxxxxxxx>
> ---

FWIW the following patch seems to be required to make it work on DPU
4.0.

https://patch.msgid.link/20261002-encoder-flush-old-ctl-v1-1-2a2f29e9b930@xxxxxxxxxxxxxxxx

I'm not 100% happy about this patch, I can foresee having issues with
the different DSC topologies, but I guess it might be easier to try
figuring them out (maybe together with rewiring / rewriting the resource
allocator). We need to find a way to try different combinations and roll
back to the smaller configuration if the other output needs more
resources.

I'll test this version, and if it passes, I will maybe try landing it...

> 2 or more SSPPs and dual-DSI interface are need for super wide panel.
> And 4 DSC are preferred for power optimal in this case due to width
> limitation of SSPP and MDP clock rate constrain. This patch set
> extends number of pipes to 4 and revise related mixer blending logic
> to support quad pipe. All these changes depends on the virtual plane
> feature to split a super wide drm plane horizontally into 2 or more sub
> clip. Thus DMA of multiple SSPPs can share the effort of fetching the
> whole drm plane.
>
> The first pipe pair co-work with the first mixer pair to cover the left
> half of screen and 2nd pair of pipes and mixers are for the right half
> of screen. If a plane is only for the right half of screen, only one
> or two of pipes in the 2nd pipe pair are valid, and no SSPP or mixer is
> assinged for invalid pipe.
>
> For those panel that does not require quad-pipe, only 1 or 2 pipes in
> the 1st pipe pair will be used. There is no concept of right half of
> screen.
>
> For legacy non virtual plane mode, the first 1 or 2 pipes are used for
> the single SSPP and its multi-rect mode.
>
> This patch set drop the merged heading 8 patches of v16, only the last
> 2 are revised and split into 4 patches here.
>
> Changes in v21:
> - Add active-CTL constrain to quad-pipe case.
> - adjust high clock rate constrain to quad-pipe case so that 4K@30Hz
> still use 2 LMs.
> - Link to v20: https://lore.kernel.org/all/20260415-msm-next-quad-pipe-split-v20-1-bc1fdf140b81@xxxxxxxxxx/
>
> Changes in v20:
> - Rebase to latest msm-next to add single DSC case into topology revison.
> - Link to v19: https://lore.kernel.org/r/20260312-msm-next-quad-pipe-split-v19-0-4ffa2b06c996@xxxxxxxxxx
>
> Changes in v19:
> - Refine the plane resource assignment to avoid unnecessary argument
> and operation for non-virtual plane case.
> - Fix wording in comments.
> - Link to v18: https://lore.kernel.org/r/20260213-msm-next-quad-pipe-split-v18-0-5815158d3635@xxxxxxxxxx
>
> Changes in v18:
> - Revise the deferring of SSPP handling and comments to distinguish
> assignment of non-virtual plane case and allocation of virtual plane case.
> - Always assume 1 stage in non-virtual plane case when splitting and
> mapping plane to pipes.
> - Revise topology decision making and comments to fix possible
> regression.
> - Link to v17: https://lore.kernel.org/r/20260121-msm-next-quad-pipe-split-v17-0-6eb6d8675ca2@xxxxxxxxxx
>
> Changes in v17:
> - Fix iommu warning on Hamoa.
> - Extract plane splitting into a dedicated function.
> - Defer plan splitting and SSPP allocation until CRTC check
> so that topology information is available.
> - Add virtual plane condition to quad-pipe topology so that
> legacy devices are not impacted.
> - Drop the merged 8 patches of v16, only the last 2 is revised
> and sent here.
> - Link to v16: https://lore.kernel.org/linux-arm-msm/20250918-v6-16-rc2-quad-pipe-upstream-4-v16-0-ff6232e3472f@xxxxxxxxxx
>
> Changes in v16:
> - Rebase to latest branch msm-next-lumag.
> - Fix IGT test failures.
> - Drop patches that have been merged.
> - Link to v15: https://lore.kernel.org/r/20250819-v6-16-rc2-quad-pipe-upstream-v15-0-2c7a85089db8@xxxxxxxxxx
>
> Changes in v15:
> - Polish logic in sspp check and assignment.
> - Link to v14: https://lore.kernel.org/r/20250801-v6-16-rc2-quad-pipe-upstream-v14-0-b626236f4c31@xxxxxxxxxx
>
> Changes in v14:
> - Add patch to fix null pointer bug SSPP sharing, which is missed in
> the last version.
> - Polish single pipe check with removing loop.
> - Polish logic of SSPP sharing test in dpu_plane_virtual_assign_resources()
> - Polish argument of dpu_plane_virtual_assign_resources().
> - Link to v13: https://lore.kernel.org/r/20250728-v6-16-rc2-quad-pipe-upstream-v13-0-954e4917fe4f@xxxxxxxxxx
>
> Changes in v13:
> - Modify the SSPP assignment patch for sharing SSPP among planes in
> quad-pipe case.
> - Link to v12: https://lore.kernel.org/r/20250707-v6-16-rc2-quad-pipe-upstream-v12-0-67e3721e7d83@xxxxxxxxxx
>
> Changes in v12:
> - Polish single pipe case detection in a plane. Add stage index check when
> sharing SSPP with multi-rect mode in 2 planes.
> - Abstract SSPP assignment in a stage into a function.
> - Rebase to latest msm/msm-next.
> - Link to v11: https://lore.kernel.org/r/20250603-v6-15-quad-pipe-upstream-v11-0-c3af7190613d@xxxxxxxxxx
>
> Changes in v11:
> - Change function name from dpu_plane_check_single_pipe to
> dpu_plane_get_single_pipe.
> - Abstract SSPP assignment in stage into a function.
> - Link to v10: https://lore.kernel.org/r/20250526-v6-15-quad-pipe-upstream-v10-0-5fed4f8897c4@xxxxxxxxxx
>
> Changes in v10:
> - Drop changes in drm helper side, because num_lm == 0 does not lead to
> any issue in the first call to dpu_plane_atomic_check_nosspp() with
> latest repo. It is initialized properly right after the call in
> drm_atomic_helper_check_planes(), thus the later plane splitting works
> as expected.
> - Rebase to latest msm-next branch.
> - Fix PIPES_PER_STAGE to PIPES_PER_PLANE where handling all pipes, instead
> of stages.
> - Link to v9: https://lore.kernel.org/r/20250506-quad-pipe-upstream-v9-0-f7b273a8cc80@xxxxxxxxxx
>
> Changes in v9:
> - Rebase to latest mainline and drop 3 patches as mainline already cover
> the logic.
> "Do not fix number of DSC"
> "configure DSC per number in use"
> "switch RM to use crtc_id rather than enc_id for allocation"
> - Add a patch to check crtc before checking plane in drm framework.
> - Add a patch to use dedicated WB number in an encoder to avoid regression.
> - Revise the condition to decide quad-pipe topology.
> - Link to v8: https://lore.kernel.org/r/20250303-sm8650-v6-14-hmd-deckard-mdss-quad-upstream-oldbootwrapper-36-prep-v8-0-eb5df105c807@xxxxxxxxxx
>
> Changes in v8:
> - Fix looping pipes of a plane in _dpu_plane_color_fill()
> - Improve pipe assignment with deleting pipes loop in stage.
> - Define PIPES_PER_PLANE properly when it appears fisrt.
> - rename lms_in_pair to lms_in_stage to avoid confusion.
> - Add review tags.
> - Link to v7: https://lore.kernel.org/r/20250226-sm8650-v6-14-hmd-deckard-mdss-quad-upstream-oldbootwrapper-36-prep-v7-0-8d5f5f426eb2@xxxxxxxxxx
>
> Changes in v7:
> - Improve pipe assignment to avoid point to invalid memory.
> - Define STAGES_PER_PLANE as 2 only when quad-pipe is introduced.
> - Polish LM number when blending pipes with min() and pull up to caller func.
> - Add review tags.
> - Link to v6: https://lore.kernel.org/r/20250217-sm8650-v6-14-hmd-deckard-mdss-quad-upstream-oldbootwrapper-36-prep-v6-0-c11402574367@xxxxxxxxxx
>
> Changes in v6:
> - Replace LM number with PP number to calculate PP number per encoder.
> - Rebase to Linux v6.14-rc2.
> - Add review tags.
> - Link to v5: https://lore.kernel.org/r/20250118-sm8650-v6-13-hmd-deckard-mdss-quad-upstream-33-v5-0-9701a16340da@xxxxxxxxxx
>
> Changes in v5:
> - Iterate SSPP flushing within the required mixer pair, instead of all
> active mixers or specific mixer.
> - Limit qaud-pipe usage case to SoC with 4 or more DSC engines and 2
> interfaces case.
> - Remove valid flag and use width for pipe validation.
> - Polish commit messages and code comments.
> - Link to v4: https://lore.kernel.org/r/20250116-sm8650-v6-13-hmd-deckard-mdss-quad-upstream-33-v4-0-74749c6eba33@xxxxxxxxxx
>
> Changes in v4:
> - Restrict SSPP flushing to the required mixer, instead of all active mixers.
> - Polish commit messages and code comments.
> - Rebase to latest msm/drm-next branch.
> - Move pipe checking patch to the top of patch set.
> - Link to v3: https://lore.kernel.org/dri-devel/20241219-sm8650-v6-13-hmd-deckard-mdss-quad-upstream-32-v3-0-92c7c0a228e3@xxxxxxxxxx
>
> Changes in v3:
> - Split change in trace into a separate patch.
> - Rebase to latest msm-next branch.
> - Reorder patch sequence to make sure valid flag is set in earlier patch
> - Rectify rewrite patch to move logic change into other patch
> - Polish commit messages and code comments.
> - Link to v2: https://lore.kernel.org/dri-devel/20241009-sm8650-v6-11-hmd-pocf-mdss-quad-upstream-21-v2-0-76d4f5d413bf@xxxxxxxxxx
>
> Changes in v2:
> - Revise the patch sequence with changing to 2 pipes topology first. Then
> prepare for quad-pipe setup, then enable quad-pipe at last.
> - Split DSI patches into other patch set.
> - Link to v1: https://lore.kernel.org/all/20240829-sm8650-v6-11-hmd-pocf-mdss-quad-upstream-8-v1-0-bdb05b4b5a2e@xxxxxxxxxx
> ---
> drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c | 55 ++++++++++++++++--------
> drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.h | 6 +--
> drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c | 29 ++++---------
> drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys.h | 2 +-
> drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.h | 2 +-
> drivers/gpu/drm/msm/disp/dpu1/dpu_hw_mdss.h | 2 +-
> 6 files changed, 52 insertions(+), 44 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> index bd0e720b484fd..d586825015906 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> @@ -200,7 +200,7 @@ static int dpu_crtc_get_lm_crc(struct drm_crtc *crtc,
> struct dpu_crtc_state *crtc_state)
> {
> struct dpu_crtc_mixer *m;
> - u32 crcs[CRTC_DUAL_MIXERS];
> + u32 crcs[CRTC_QUAD_MIXERS];
>
> int rc = 0;
> int i;
> @@ -1384,6 +1384,9 @@ static struct msm_display_topology dpu_crtc_get_topology(
> struct drm_display_mode *mode = &crtc_state->adjusted_mode;
> struct msm_display_topology topology = {0};
> struct drm_encoder *drm_enc;
> + struct msm_drm_private *priv = crtc->dev->dev_private;
> + struct dpu_kms *kms = to_dpu_kms(priv->kms);
> + u32 num_rt_intf;
>
> drm_for_each_encoder_mask(drm_enc, crtc->dev, crtc_state->encoder_mask)
> dpu_encoder_update_topology(drm_enc, &topology, crtc_state->state,
> @@ -1396,32 +1399,48 @@ static struct msm_display_topology dpu_crtc_get_topology(
> *
> * Dual display
> * 2 LM, 2 INTF ( Split display using 2 interfaces)
> + * 4 LM, 2 INTF ( Split display using 2 interfaces and stream merge
> + to support high resolution interfaces if virtual
> + plane is enabled)
> + * If DSC is enabled, use 2:2:2 for 2 LMs case, and 4:4:2 for 4 LMs
> + * case.
> *
> * Single display
> * 1 LM, 1 INTF
> * 2 LM, 1 INTF (stream merge to support high resolution interfaces)
> *
> - * If DSC is enabled, use 2 LMs for 2:2:1 topology
> + * If DSC is enabled, use 2 LMs for 2:2:1 topology for single display
> + * to support legacy devices that use this topology. Use 1:1:1 topology
> + * if there is only one DSC engine in SoC.
> *
> * Add dspps to the reservation requirements if ctm or gamma_lut are requested
> - *
> - * Only hardcode num_lm to 2 for cases where num_intf == 2 and CWB is not
> - * enabled. This is because in cases where CWB is enabled, num_intf will
> - * count both the WB and real-time phys encoders.
> - *
> - * For non-DSC CWB usecases, have the num_lm be decided by the
> - * (mode->hdisplay > MAX_HDISPLAY_SPLIT) check.
> */
>
> - if (topology.num_intf == 2 && !topology.cwb_enabled)
> - topology.num_lm = 2;
> - else if (topology.num_dsc == 2)
> - topology.num_lm = 2;
> - else if (dpu_kms->catalog->caps->has_3d_merge &&
> - topology.num_dsc == 0)
> - topology.num_lm = (mode->hdisplay > MAX_HDISPLAY_SPLIT) ? 2 : 1;
> - else
> - topology.num_lm = 1;
> + num_rt_intf = topology.num_intf;
> + if (topology.cwb_enabled)
> + num_rt_intf--;
> +
> + if ((mode->hdisplay > (dpu_kms->catalog->caps->max_mixer_width * num_rt_intf)) ||
> + ((u64)mode->hdisplay * mode->vtotal * drm_mode_vrefresh(mode) >
> + kms->perf.max_core_clk_rate))
> + topology.num_lm = num_rt_intf * 2;
> + else {
> + topology.num_lm = (mode->hdisplay > MAX_HDISPLAY_SPLIT) ?
> + 2 : num_rt_intf;
> + }
> +
> + if (!dpu_use_virtual_planes ||
> + dpu_kms->catalog->mdss_ver->core_major_ver < 5)
> + topology.num_lm = min(2, topology.num_lm);
> +
> + if (!dpu_kms->catalog->caps->has_3d_merge)
> + topology.num_lm = min(num_rt_intf, topology.num_lm);
> +
> + if (topology.num_dsc) {
> + if (num_rt_intf == 1)
> + topology.num_lm = min(2, dpu_kms->catalog->dsc_count);
> + topology.num_dsc = topology.num_lm;
> + }
>
> if (crtc_state->ctm || crtc_state->gamma_lut)
> topology.num_dspp = topology.num_lm;
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.h b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.h
> index 6eaba5696e8e6..455073c7025b0 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.h
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.h
> @@ -210,7 +210,7 @@ struct dpu_crtc_state {
>
> bool bw_control;
> bool bw_split_vote;
> - struct drm_rect lm_bounds[CRTC_DUAL_MIXERS];
> + struct drm_rect lm_bounds[CRTC_QUAD_MIXERS];
>
> uint64_t input_fence_timeout_ns;
>
> @@ -218,10 +218,10 @@ struct dpu_crtc_state {
>
> /* HW Resources reserved for the crtc */
> u32 num_mixers;
> - struct dpu_crtc_mixer mixers[CRTC_DUAL_MIXERS];
> + struct dpu_crtc_mixer mixers[CRTC_QUAD_MIXERS];
>
> u32 num_ctls;
> - struct dpu_hw_ctl *hw_ctls[CRTC_DUAL_MIXERS];
> + struct dpu_hw_ctl *hw_ctls[CRTC_QUAD_MIXERS];
>
> enum dpu_crtc_crc_source crc_source;
> int crc_frame_skip_count;
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> index eba1d52211f68..058a7c8727f7c 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> @@ -55,7 +55,7 @@
> #define MAX_PHYS_ENCODERS_PER_VIRTUAL \
> (MAX_H_TILES_PER_DISPLAY * NUM_PHYS_ENCODER_TYPES)
>
> -#define MAX_CHANNELS_PER_ENC 2
> +#define MAX_CHANNELS_PER_ENC 4
> #define MAX_CWB_PER_ENC 2
>
> #define IDLE_SHORT_TIMEOUT 1
> @@ -661,7 +661,6 @@ void dpu_encoder_update_topology(struct drm_encoder *drm_enc,
> struct dpu_encoder_virt *dpu_enc = to_dpu_encoder_virt(drm_enc);
> struct msm_drm_private *priv = dpu_enc->base.dev->dev_private;
> struct msm_display_info *disp_info = &dpu_enc->disp_info;
> - struct dpu_kms *dpu_kms = to_dpu_kms(priv->kms);
> struct drm_connector *connector;
> struct drm_connector_state *conn_state;
> struct drm_framebuffer *fb;
> @@ -675,22 +674,12 @@ void dpu_encoder_update_topology(struct drm_encoder *drm_enc,
>
> dsc = dpu_encoder_get_dsc_config(drm_enc);
>
> - /* We only support 2 DSC mode (with 2 LM and 1 INTF) */
> - if (dsc) {
> - /*
> - * Use 2 DSC encoders, 2 layer mixers and 1 or 2 interfaces
> - * 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.
> - */
> - WARN(topology->num_intf > 2,
> - "DSC topology cannot support more than 2 interfaces\n");
> - if (topology->num_intf >= 2 || dpu_kms->catalog->dsc_count >= 2)
> - topology->num_dsc = 2;
> - else
> - topology->num_dsc = 1;
> - }
> + /*
> + * Set DSC number as 1 to mark the enabled status, will be adjusted
> + * in dpu_crtc_get_topology()
> + */
> + if (dsc)
> + topology->num_dsc = 1;
>
> connector = drm_atomic_get_new_connector_for_encoder(state, drm_enc);
> if (!connector)
> @@ -2180,8 +2169,8 @@ static void dpu_encoder_helper_reset_mixers(struct dpu_encoder_phys *phys_enc)
> {
> int i, num_lm;
> struct dpu_global_state *global_state;
> - struct dpu_hw_blk *hw_lm[2];
> - struct dpu_hw_mixer *hw_mixer[2];
> + struct dpu_hw_blk *hw_lm[MAX_CHANNELS_PER_ENC];
> + struct dpu_hw_mixer *hw_mixer[MAX_CHANNELS_PER_ENC];
> struct dpu_hw_ctl *ctl = phys_enc->hw_ctl;
>
> /* reset all mixers for this encoder */
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys.h b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys.h
> index 61b22d9494546..09395d7910ac8 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys.h
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys.h
> @@ -302,7 +302,7 @@ static inline enum dpu_3d_blend_mode dpu_encoder_helper_get_3d_blend_mode(
>
> /* Use merge_3d unless DSC MERGE topology is used */
> if (phys_enc->split_role == ENC_ROLE_SOLO &&
> - dpu_cstate->num_mixers == CRTC_DUAL_MIXERS &&
> + (dpu_cstate->num_mixers != 1) &&
> !dpu_encoder_use_dsc_merge(phys_enc->parent))
> return BLEND_3D_H_ROW_INT;
>
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.h b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.h
> index ba04ac24d5a9e..b1ac84c0b52db 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.h
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.h
> @@ -24,7 +24,7 @@
> #define DPU_MAX_IMG_WIDTH 0x3fff
> #define DPU_MAX_IMG_HEIGHT 0x3fff
>
> -#define CRTC_DUAL_MIXERS 2
> +#define CRTC_QUAD_MIXERS 4
>
> #define MAX_XIN_COUNT 16
>
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_mdss.h b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_mdss.h
> index 0e65bf5ddc4a6..fd1f3e7982062 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_mdss.h
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_mdss.h
> @@ -34,7 +34,7 @@
> #define DPU_MAX_PLANES 4
> #endif
>
> -#define STAGES_PER_PLANE 1
> +#define STAGES_PER_PLANE 2
> #define PIPES_PER_STAGE 2
> #define PIPES_PER_PLANE (PIPES_PER_STAGE * STAGES_PER_PLANE)
> #ifndef DPU_MAX_DE_CURVES
>
> ---
> base-commit: a913d08e5ea9a491b806e64a24410f6722ddc9b3
> change-id: 20260121-msm-next-quad-pipe-split-ab95b6e3ffd3
>
> Best regards,
> --
> Jun Nie <jun.nie@xxxxxxxxxx>
>

--
With best wishes
Dmitry