kernel/linux.git/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.h, branch master

drm/amd/display: Move FPU Guards From DML To DC - Part 1

2026-03-30T19:06:10+00:00

[Why] FPU guards (DC_FP_START/DC_FP_END) are required to wrap around code that can manipulates floats. To do this properly, the FPU guards must be used in a file that is not compiled as a FPU unit. If the guards are used in a file that is a FPU unit, other sections in the file that aren't guarded may be end up being compiled to use FPU operations. [How] Added DC_FP_START and DC_FP_END to DC functions that call DML functions using FPU. Reviewed-by: Dillon Varone Signed-off-by: Rafal Ostrowski Signed-off-by: Alex Hung Signed-off-by: Alex Deucher

drm/amd/display: Permit DC_FP_START/END only in non-FP compilation units

2025-12-08T18:56:37+00:00

[WHAT] Test the existing CPP macro _LINUX_FPU_COMPILATION_UNIT, which is set when building source files that are permitted to use floating point, in the implementation of DC_FP_START/END so that those are only usable in non-FP code. This is a requirement of the generic kernel mode FPU API, as some architectures (i.e., arm64) cannot safely enable FP codegen in arbitrary code. Cc: Austin Zheng Cc: Jun Lei Cc: Harry Wentland Cc: Leo Li Cc: Rodrigo Siqueira Cc: Alex Deucher Cc: "Christian König" Cc: amd-gfx@lists.freedesktop.org Cc: dri-devel@lists.freedesktop.org Suggested-by: Christian König Acked-by: Christian König Reviewed-by: Alex Hung Signed-off-by: Ard Biesheuvel Signed-off-by: Alex Hung Tested-by: Dan Wheeler Signed-off-by: Alex Deucher

drm/amd/display: Add DC_FP helper to check FPU state

2021-08-06T01:17:59+00:00

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. Note that 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. Nevertheless, it is the programmer's responsibility to invoke DC_FP_START/END in the correct place. 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. Changes cince V3: - Rebase Changes cince V2 (Christian): - Do not use this_cpu_* between get/put_cpu_ptr(). - In the kernel documentation, better describe restrictions. - Make dc_assert_fp_enabled trigger the ASSERT message. Changes since V1: - Remove fp_enable variables - Rename dc_is_fp_enabled to dc_assert_fp_enabled - Replace wrong variable type Cc: Harry Wentland Cc: Anson Jacob Cc: Christian König Cc: Hersen Wu Cc: Aric Cyr Cc: Jun Lei Cc: Dmytro Laktyushkin Cc: Qingqing Zhuo Reported-by: kernel test robot Signed-off-by: Rodrigo Siqueira Reviewed-by: Christian König Signed-off-by: Alex Deucher

drm/amd/display: Add control mechanism for FPU

2021-08-06T01:17:59+00:00

DC invokes DC_FPU_START/END in multiple parts of the code; this can create a situation where we invoke this FPU operation in a nested way or exit too early. For avoiding this situation, this commit adds a mechanism where dc_fpu_begin/end manages the access to kernel_fpu_begin/end. Change since V3: - Christian: Move PPC64 code to dc_fpu_begin/end. Change since V2: - Christian: Do not use this_cpu_* between get/put_cpu_ptr(). Change since V1: - Use a better variable names - Use get_cpu_ptr and put_cpu_ptr to better balance preemption enable and disable Cc: Harry Wentland Cc: Anson Jacob Cc: Christian König Cc: Hersen Wu Cc: Aric Cyr Cc: Jun Lei Cc: Dmytro Laktyushkin Cc: Qingqing Zhuo Signed-off-by: Rodrigo Siqueira Reviewed-by: Christian König Signed-off-by: Alex Deucher