dcn32_assign_subvp_pipe(9)

✨ dcn32_assign_subvp_pipe ✨

okay bestie, so this is a page from the Kernel API Manual — it's all about dcn32_assign_subvp_pipe, the function that decides which pipe gets to use Sub-VP 💅

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🌸 SYNOPSIS 🌸

bool dcn32_assign_subvp_pipe (struct dc *dc , struct dc_state *context ,
unsigned int *index );

like, it returns a bool, takes a dc, a context, and an index — that's the whole squad right there 🫶

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🎀 ARGUMENTS 🎀

• dc — the current dc state, i.e. what's happening right now bestie
• context — the new dc state, the glow-up we're considering ✨
• index — [out] parameter! it hands you back the dc pipe index for the pipe that got chosen to have phantom pipes assigned 👑

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🦋 DESCRIPTION 🦋

so here's the vibe check 💀 — we only even enter this function if we're Sub-VP capable (translation: enough pipes are available) and regular P-State switching (that's VACTIVE/VBLANK, iykyk) is not supported. OR we're in there because we're forcing SubVP P-State switching on the current config. either way, we're in it now 🔥

the rule, no cap: the number of pipes used for the chosen surface has to be less than or equal to the number of free pipes available. that's non-negotiable, fr fr 🧚

in general? we pick surfaces with the longest frame time first — that's better for SubVP + VBLANK, periodt 👑

but for the multi-display cases, ActiveDRAMClockChangeMargin lowkey doesn't give us enough info on its own to figure out which one should be the SubVP pipe 😭 we need a way to determine if a pipe / plane doesn't support MCLK switching naturally (like ACTIVE or VBLANK) — that's the missing piece, and it's giving unresolved plotline ngl 🙈

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⭐ RETURN ⭐

• True — slay 💖 a valid pipe assignment was found for Sub-VP
• False — nope 🙈 no valid assignment for you

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👑 SEE ALSO 👑

the source file itself lives at ./drivers/gpu/drm/amd/display/dc/dml/dcn32/dcn32_fpu.c — like, that's the whole address bestie 🏠

and here's the whole friend group, all of them iconic, all of them (9):

• dcn32_helper_populate_phantom_dlg_params(9)
• dcn32_set_phantom_stream_timing(9)
• dcn32_get_num_free_pipes(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 whole page, bestie 🫶 this one came out of ./drivers/gpu/drm/amd/display/... with a date stamp of October 2026, served up hot from the Kernel API Manual — go read the other dcn32_* pages, they're literally so good, mwah 💋🌈