dcn32_set_p...tream_timing(9)

✨ NAME ✨

dcn32_set_phantom_stream_timing — bestie, this is the one that sets the timing params for the phantom stream 👻 like it's giving main-character-but-invisible energy, no cap

(also hi, you're reading a page from the Kernel API Manual, welcome to the group chat 💅)

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🦋 SYNOPSIS 🦋

void dcn32_set_phantom_stream_timing (struct dc *dc , struct dc_state
*context , struct pipe_ctx *ref_pipe , struct dc_stream_state
*phantom_stream , display_e2e_pipe_params_st *pipes , unsigned int
pipe_cnt , unsigned int dc_pipe_idx );

literally that's the whole signature, copy it exactly, don't come for me about the spacing, that's how it is 🫶

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🎀 ARGUMENTS 🎀

okay so here's the cast of characters, and yes every single one of them matters:

• dc — the current dc state, like the present-tense vibe
• context — the new dc state, the glow-up version
• ref_pipe — the main pipe for the phantom stream, i.e. the reference point, the blueprint, the blueprint-iest 🧚
• phantom_stream — target phantom stream state (the ghostie we're setting up)
• pipes — DML pipe params
• pipe_cnt — number of DML pipes, keep count bestie
• dc_pipe_idx — DC pipe index for the main pipe (i.e. ref_pipe), yes they wrote "i.e." so I'm keeping the "i.e."

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🔥 DESCRIPTION 🔥

So what does this actually do? It sets the timing params of the phantom stream based on the calculated output from DML. 💫

The way it works: first it gets the DML pipe index using the DC pipe index (a whole little translation moment, iykyk), then it calls into DML (get_subviewport_lines_needed_in_mall) to get the number of lines required for SubVP MCLK switching — and then it assigns that to the phantom stream accordingly. Iconic, honestly.

Two things you need to hold onto, and I'm saying them exactly because they're load-bearing:

• The number of SubVP lines calculated in DML does not take into account FW processing delays and required pstate allow width, so we must include that separately. ⚠️ (not me reminding you twice)
• Set phantom backporch = vstartup of main pipe

that second bullet is not a suggestion bestie, that's the assignment 📝

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👑 SEE ALSO 👑

go read these next, the whole friend group:

• Kernel file ./drivers/gpu/drm/amd/display/dc/dml/dcn32/dcn32_fpu.c
• dcn32_helper_populate_phantom_dlg_params(9)
• dcn32_get_num_free_pipes(9)
• dcn32_assign_subvp_pipe(9)
• dcn32_enough_pipes_for_subvp(9)
• subvp_subvp_schedulable(9)
• subvp_drr_schedulable(9)
• subvp_vblank_schedulable(9)
• subvp_subvp_admissable(9)
• subvp_validate_static_schedulability(9)
• dcn32_allow_subvp_high_refresh_rate(9)
• dcn32_determine_max_vratio_prefetch(9)
• dcn32_assign_fpo_vactive_candidate(9)
• dcn32_find_vactive_pipe(9)

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and that's the page bestie, you ate that 💖

cute little sign-off before you go: this one comes from ./drivers/gpu/drm/amd/display/..., dated October 2026, and the footer names it dcn32_set_p...tream_timing(9) — yeah the title got truncated in the footer, she's a little mysterious like that 🙈 slay 🎀