DCN2X FPU MANIPULATION OVERVIEW(9)

💅 DCN2x FPU manipulation Overview 💅

Okay bestie, welcome to the Kernel API Manual entry for DCN2x FPU manipulation Overview — yes the header line got chopped to DCN2x FPU m...ion Overview(9) up top, we're keeping it cute and mysterious like that ✨

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🦋 the whole situation 🦋

So. The DCN architecture relies on FPU operations, which means it needs special compilation flags and the use of the kernel_fpu_begin/end functions. And ideally? We want to avoid spreading FPU access across multiple files — it's giving messy, it's giving chaos, we don't want it 💀

With that idea in mind, this file aims to centralize all DCN20 and DCN2.1 (DCN2x) functions that require FPU access in a single place. One file. One vibe. One home 🏠✨

Code in this file follows the following code pattern:

1. Functions that use FPU operations should be isolated in static functions.
2. The FPU functions should have the noinline attribute to ensure anything that deals with FP register is contained within this call.
3. All function that needs to be accessed outside this file requires a public interface that not uses any FPU reference.
4. Developers must not use DC_FP_START/END in this file, but they need to ensure that the caller invokes it before access any function available in this file. For this reason, public functions in this file must invoke dc_assert_fp_enabled;

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💖 let's expand a lil bit more on that 💖

To fully isolate FPU operations in a single place, we must avoid situations where compilers spill FP values to registers due to FP enable in a specific C file. Like, even if we isolate all FPU functions in a single file and call its interface from other files, the compiler might enable the use of FPU before we call DC_FP_START. Sneaky. Rude. 🙈

Nevertheless — and this part is important, bestie — it is the programmer's responsibility to invoke DC_FP_START/END in the correct place. No cap. That's on you 🫶

To highlight situations where developers forgot to use the FP protection before calling the DC FPU interface functions, we introduce a helper that checks if the function is invoked under FP protection. If not, it will trigger a kernel warning 🔥👑

⚠️ real talk: forgetting the FP protection is not a slay, it's a kernel warning. Protect your FP, protect your peace 💅

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🌈 SEE ALSO 🌈

• Kernel file ./drivers/gpu/drm/amd/display/dc/dml/dcn20/dcn20_fpu.c — go read it, iykyk 📖✨

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mwah 💋 that's the whole page — sourced from ./drivers/gpu/drm/amd/display/..., dated October 2026, and yes the footer also says DCN2x FPU m...ion Overview(9) because the truncation is iconic at this point. bye bestie, go write some static functions 🎀🦋💜