r600_vram_gtt_location(9)

💅 r600_vram_gtt_location(9) — Kernel API Manual, bestie edition ✨

okay so real talk, this one's from the Kernel API Manual and it's literally about finding a home for your VRAM and GTT. let's get into it 🎀

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✨ NAME ✨

r600_vram_gtt_location — the function that tries to figure out where VRAM & GTT should live 🏠

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🦋 SYNOPSIS 🦋

void r600_vram_gtt_location (struct radeon_device *rdev , struct
       radeon_mc *mc );

like, it returns void and takes two pointers. that's it. that's the whole vibe check. 💅

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🌸 ARGUMENTS 🌸

• rdev — the radeon device structure, and she's holding all the necessary informations. everything. the whole lore. 📚
• mc — the memory controller structure, holding all the memory informations. this is where the actual memory tea lives. 🫖

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💖 DESCRIPTION 💖

okay so here's the situation. this function will place (well, try to place) VRAM at the same place as in the CPU (PCI) address space, because some GPUs genuinely seem to have issues when we reprogram them at a different address space. like, they just get weird about it. 🙈 so we keep things where they expect them.

if there isn't enough space to fit the unvisible VRAM after the aperture? no worries, no panic — we just limit the VRAM size to the aperture. problem solved, slay. ✨

and if we're using AGP, then we place VRAM adjacent to the AGP aperture, because we need them both to be in one from the GPU's point of view — that way we can program the GPU to catch access outside them. yes it's a weird GPU policy (see ??). iconic behavior honestly. 💀

the big flex here: this function will never fail. like, ever. worst case scenario, she's just limiting VRAM or GTT. no crash, no drama, just limits. periodt. 👑

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⭐ NOTE ⭐

ngl this part matters: on the AGP platform, the GTT start, end, and size should already be initialized before you call this function. do not come in here unprepared bestie. 🙏

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🔥 SEE ALSO 🔥

• Kernel file ./drivers/gpu/drm/radeon/r600.c
• r600_get_allowed_info_register(9)
• r600_get_xclk(9)
• r600_gfx_is_lockup(9)
• r600_semaphore_ring_emit(9)
• r600_copy_cpdma(9)
• r600_mmio_hdp_flush(9)
• r600_get_gpu_clock_counter(9)

like, the whole friend group. go read them too, you won't regret it. 💜

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reminder bestie: this page ships with the files under ./drivers/gpu/drm/radeon, and it's dated October 2026 — so yes, she's from the future, and she still ate. 💅✨

🫶 that's the whole page, love u, go place some VRAM correctly 🎀