[PATCH 3/3] drm/amd/display: Support DRM_AMD_DC_FP on RISC-V

[Samuel Holland]

RISC-V uses kernel_fpu_begin()/kernel_fpu_end() like several other
architectures. Enabling hardware FP requires overriding the ISA string
for the relevant compilation units.

Signed-off-by: Samuel Holland <samuel.holland at sifive.com>
---

 drivers/gpu/drm/amd/display/Kconfig            | 5 ++++-
 drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c | 6 ++++--
 drivers/gpu/drm/amd/display/dc/dml/Makefile    | 6 ++++++
 drivers/gpu/drm/amd/display/dc/dml2/Makefile   | 6 ++++++
 4 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/Kconfig b/drivers/gpu/drm/amd/display/Kconfig
index 901d1961b739..49b33b2f6701 100644
--- a/drivers/gpu/drm/amd/display/Kconfig
+++ b/drivers/gpu/drm/amd/display/Kconfig
@@ -8,7 +8,10 @@ config DRM_AMD_DC
 	depends on BROKEN || !CC_IS_CLANG || ARM64 || RISCV || SPARC64 || X86_64
 	select SND_HDA_COMPONENT if SND_HDA_CORE
 	# !CC_IS_CLANG: https://github.com/ClangBuiltLinux/linux/issues/1752
-	select DRM_AMD_DC_FP if (X86 || LOONGARCH || (PPC64 && ALTIVEC) || (ARM64 && KERNEL_MODE_NEON && !CC_IS_CLANG))
+	select DRM_AMD_DC_FP if ARM64 && KERNEL_MODE_NEON && !CC_IS_CLANG
+	select DRM_AMD_DC_FP if PPC64 && ALTIVEC
+	select DRM_AMD_DC_FP if RISCV && FPU
+	select DRM_AMD_DC_FP if LOONGARCH || X86
 	help
 	  Choose this option if you want to use the new display engine
 	  support for AMDGPU. This adds required support for Vega and
diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c b/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c
index 4ae4720535a5..834dca0396f1 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c
@@ -35,6 +35,8 @@
 #include <asm/neon.h>
 #elif defined(CONFIG_LOONGARCH)
 #include <asm/fpu.h>
+#elif defined(CONFIG_RISCV)
+#include <asm/switch_to.h>
 #endif
 
 /**
@@ -89,7 +91,7 @@ void dc_fpu_begin(const char *function_name, const int line)
 	depth = __this_cpu_inc_return(fpu_recursion_depth);
 
 	if (depth == 1) {
-#if defined(CONFIG_X86) || defined(CONFIG_LOONGARCH)
+#if defined(CONFIG_X86) || defined(CONFIG_LOONGARCH) || defined(CONFIG_RISCV)
 		kernel_fpu_begin();
 #elif defined(CONFIG_PPC64)
 		if (cpu_has_feature(CPU_FTR_VSX_COMP))
@@ -122,7 +124,7 @@ void dc_fpu_end(const char *function_name, const int line)
 
 	depth = __this_cpu_dec_return(fpu_recursion_depth);
 	if (depth == 0) {
-#if defined(CONFIG_X86) || defined(CONFIG_LOONGARCH)
+#if defined(CONFIG_X86) || defined(CONFIG_LOONGARCH) || defined(CONFIG_RISCV)
 		kernel_fpu_end();
 #elif defined(CONFIG_PPC64)
 		if (cpu_has_feature(CPU_FTR_VSX_COMP))
diff --git a/drivers/gpu/drm/amd/display/dc/dml/Makefile b/drivers/gpu/drm/amd/display/dc/dml/Makefile
index ea7d60f9a9b4..5c8f840ef323 100644
--- a/drivers/gpu/drm/amd/display/dc/dml/Makefile
+++ b/drivers/gpu/drm/amd/display/dc/dml/Makefile
@@ -43,6 +43,12 @@ dml_ccflags := -mfpu=64
 dml_rcflags := -msoft-float
 endif
 
+ifdef CONFIG_RISCV
+include $(srctree)/arch/riscv/Makefile.isa
+# Remove V from the ISA string, like in arch/riscv/Makefile, but keep F and D.
+dml_ccflags := -march=$(shell echo $(riscv-march-y) | sed -E 's/(rv32ima|rv64ima)([^v_]*)v?/\1\2/')
+endif
+
 ifdef CONFIG_CC_IS_GCC
 ifneq ($(call gcc-min-version, 70100),y)
 IS_OLD_GCC = 1
diff --git a/drivers/gpu/drm/amd/display/dc/dml2/Makefile b/drivers/gpu/drm/amd/display/dc/dml2/Makefile
index acff3449b8d7..15ad6e3a2173 100644
--- a/drivers/gpu/drm/amd/display/dc/dml2/Makefile
+++ b/drivers/gpu/drm/amd/display/dc/dml2/Makefile
@@ -42,6 +42,12 @@ dml2_ccflags := -mfpu=64
 dml2_rcflags := -msoft-float
 endif
 
+ifdef CONFIG_RISCV
+include $(srctree)/arch/riscv/Makefile.isa
+# Remove V from the ISA string, like in arch/riscv/Makefile, but keep F and D.
+dml2_ccflags := -march=$(shell echo $(riscv-march-y) | sed -E 's/(rv32ima|rv64ima)([^v_]*)v?/\1\2/')
+endif
+
 ifdef CONFIG_CC_IS_GCC
 ifeq ($(call cc-ifversion, -lt, 0701, y), y)
 IS_OLD_GCC = 1
-- 
2.42.0