[PATCH v4 0/1] drm/amd/display: add DCN support for ARM64

[Ao Zhong]

Hello everyone,

Recently I got a SBSA ARM64 workstation, and try to use it as my daily
drive machine after installing an AMD RX6400 graphics card.

Since the newer AMD GPUs require DCN (Display Core Next) support to work
properly, DCN is not supported on ARM64 platforms. Because some code in
DCN needs to use FPU, and aarch64 has no soft floating-point toolchain.

Displaycore developers have started isolating code that needs to use
FPU, and most of the code has been isolated. In the process of trying to
enable DCN support for the ARM64 platform, I found that there are two
remaining code blocks that are not isolated. Due to -mgeneral-regs-only
is enabled by default to compile the kernel on the ARM64 platform, these
two code blocks will cause the compilation to fail after enabling DCN
support.

I have submitted two patches to isolate the remaining two code blocks
that need to use the FPU.
Links: https://patchwork.freedesktop.org/patch/508813/
Links: https://patchwork.freedesktop.org/patch/508816/
After merging these two patches, we can enable DCN support for ARM64
platform.

I removed -mgeneral-regs-only CFLAG in the dml/Makefile for the code
that needs to use hardware FPU, and add a control mechanism in
amdgpu_dm/dc_fpu.c for ARM Neon.

Change Since V3:
- Check if CC_IS_CLANG is disabled, since current DCN build with clang
  on ARM64 is broken

Change Since V2:
- Drop CONFIG_DRM_AMD_DC_DCN check when initializing the dml_rcflags
  for ARM64
- Drop CONFIG_ARM64 and CONFIG_DRM_AMD_DC_DCN check for the per-file
  cflags list entirely

Change Since V1:
- replace $(dml_rcflags_arm64) with $(dml_rcflags) in dml/Makefile

Ao Zhong (1):
  drm/amd/display: add DCN support for ARM64

 drivers/gpu/drm/amd/display/Kconfig           |  3 ++-
 .../gpu/drm/amd/display/amdgpu_dm/dc_fpu.c    |  6 ++++++
 drivers/gpu/drm/amd/display/dc/dml/Makefile   | 20 +++++++++++++++----
 3 files changed, 24 insertions(+), 5 deletions(-)

-- 
2.37.4