Re: [PATCH -stable] drm/amdgpu/display: drop DCN support for aarch64

Harry Wentland
2021-01-21T16:43:01Z

On 2021-01-21 4:20 a.m., Ard Biesheuvel wrote:
> From: Alex Deucher <alexander.deucher@amd.com>
>
> commit c241ed2f0ea549c18cff62a3708b43846b84dae3 upstream.
>
> From Ard:
>
> "Simply disabling -mgeneral-regs-only left and right is risky, given that
> the standard AArch64 ABI permits the use of FP/SIMD registers anywhere,
> and GCC is known to use SIMD registers for spilling, and may invent
> other uses of the FP/SIMD register file that have nothing to do with the
> floating point code in question. Note that putting kernel_neon_begin()
> and kernel_neon_end() around the code that does use FP is not sufficient
> here, the problem is in all the other code that may be emitted with
> references to SIMD registers in it.
>
> So the only way to do this properly is to put all floating point code in
> a separate compilation unit, and only compile that unit with
> -mgeneral-regs-only."
>
> Disable support until the code can be properly refactored to support this
> properly on aarch64.
>
> Acked-by: Will Deacon <will@kernel.org>
> Reported-by: Ard Biesheuvel <ardb@kernel.org>
> Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
> [ardb: backport to v5.10 by reverting c38d444e44badc55 instead]
> Acked-by: Alex Deucher <alexander.deucher@amd.com> # v5.10 backport

Acked-by: Harry Wentland <harry.wentland@amd.com>

Harry

> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> ---
> The original commit does not apply cleanly to v5.10, as it reverts a
> combination of patches, some of which are not present in v5.10.
>
> This patch is a straight revert of c38d444e44badc55, which is the only
> change that needs to be backed out from v5.10, and amounts to the same
> thing as the original mainline commit.
>
> drivers/gpu/drm/amd/display/Kconfig | 2 +-
> drivers/gpu/drm/amd/display/dc/calcs/Makefile | 7 --
> drivers/gpu/drm/amd/display/dc/clk_mgr/Makefile | 7 --
> drivers/gpu/drm/amd/display/dc/dcn10/Makefile | 7 --
> drivers/gpu/drm/amd/display/dc/dcn10/dcn10_resource.c | 81 ++++++++------------
> drivers/gpu/drm/amd/display/dc/dcn20/Makefile | 4 -
> drivers/gpu/drm/amd/display/dc/dcn21/Makefile | 4 -
> drivers/gpu/drm/amd/display/dc/dml/Makefile | 13 ----
> drivers/gpu/drm/amd/display/dc/dsc/Makefile | 5 --
> drivers/gpu/drm/amd/display/dc/os_types.h | 4 -
> 10 files changed, 32 insertions(+), 102 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/display/Kconfig b/drivers/gpu/drm/amd/display/Kconfig
> index 60dfdd432aba..3c410d236c49 100644
> --- a/drivers/gpu/drm/amd/display/Kconfig
> +++ b/drivers/gpu/drm/amd/display/Kconfig
> @@ -6,7 +6,7 @@ config DRM_AMD_DC
> bool "AMD DC - Enable new display engine"
> default y
> select SND_HDA_COMPONENT if SND_HDA_CORE
> - select DRM_AMD_DC_DCN if (X86 || PPC64 || (ARM64 && KERNEL_MODE_NEON)) && !(KCOV_INSTRUMENT_ALL && KCOV_ENABLE_COMPARISONS)
> + select DRM_AMD_DC_DCN if (X86 || PPC64) && !(KCOV_INSTRUMENT_ALL && KCOV_ENABLE_COMPARISONS)
> 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/dc/calcs/Makefile b/drivers/gpu/drm/amd/display/dc/calcs/Makefile
> index 64f515d74410..4674aca8f206 100644
> --- a/drivers/gpu/drm/amd/display/dc/calcs/Makefile
> +++ b/drivers/gpu/drm/amd/display/dc/calcs/Makefile
> @@ -33,10 +33,6 @@ ifdef CONFIG_PPC64
> calcs_ccflags := -mhard-float -maltivec
> endif
>
> -ifdef CONFIG_ARM64
> -calcs_rcflags := -mgeneral-regs-only
> -endif
> -
> ifdef CONFIG_CC_IS_GCC
> ifeq ($(call cc-ifversion, -lt, 0701, y), y)
> IS_OLD_GCC = 1
> @@ -57,9 +53,6 @@ endif
> CFLAGS_$(AMDDALPATH)/dc/calcs/dcn_calcs.o := $(calcs_ccflags)
> CFLAGS_$(AMDDALPATH)/dc/calcs/dcn_calc_auto.o := $(calcs_ccflags)
> CFLAGS_$(AMDDALPATH)/dc/calcs/dcn_calc_math.o := $(calcs_ccflags) -Wno-tautological-compare
> -CFLAGS_REMOVE_$(AMDDALPATH)/dc/calcs/dcn_calcs.o := $(calcs_rcflags)
> -CFLAGS_REMOVE_$(AMDDALPATH)/dc/calcs/dcn_calc_auto.o := $(calcs_rcflags)
> -CFLAGS_REMOVE_$(AMDDALPATH)/dc/calcs/dcn_calc_math.o := $(calcs_rcflags)
>
> BW_CALCS = dce_calcs.o bw_fixed.o custom_float.o
>
> diff --git a/drivers/gpu/drm/amd/display/dc/clk_mgr/Makefile b/drivers/gpu/drm/amd/display/dc/clk_mgr/Makefile
> index 1a495759a034..52b1ce775a1e 100644
> --- a/drivers/gpu/drm/amd/display/dc/clk_mgr/Makefile
> +++ b/drivers/gpu/drm/amd/display/dc/clk_mgr/Makefile
> @@ -104,13 +104,6 @@ ifdef CONFIG_PPC64
> CFLAGS_$(AMDDALPATH)/dc/clk_mgr/dcn21/rn_clk_mgr.o := $(call cc-option,-mno-gnu-attribute)
> endif
>
> -# prevent build errors:
> -# ...: '-mgeneral-regs-only' is incompatible with the use of floating-point types
> -# this file is unused on arm64, just like on ppc64
> -ifdef CONFIG_ARM64
> -CFLAGS_REMOVE_$(AMDDALPATH)/dc/clk_mgr/dcn21/rn_clk_mgr.o := -mgeneral-regs-only
> -endif
> -
> AMD_DAL_CLK_MGR_DCN21 = $(addprefix $(AMDDALPATH)/dc/clk_mgr/dcn21/,$(CLK_MGR_DCN21))
>
> AMD_DISPLAY_FILES += $(AMD_DAL_CLK_MGR_DCN21)
> diff --git a/drivers/gpu/drm/amd/display/dc/dcn10/Makefile b/drivers/gpu/drm/amd/display/dc/dcn10/Makefile
> index 733e6e6e43bd..62ad1a11bff9 100644
> --- a/drivers/gpu/drm/amd/display/dc/dcn10/Makefile
> +++ b/drivers/gpu/drm/amd/display/dc/dcn10/Makefile
> @@ -31,11 +31,4 @@ DCN10 = dcn10_init.o dcn10_resource.o dcn10_ipp.o dcn10_hw_sequencer.o \
>
> AMD_DAL_DCN10 = $(addprefix $(AMDDALPATH)/dc/dcn10/,$(DCN10))
>
> -# fix:
> -# ...: '-mgeneral-regs-only' is incompatible with the use of floating-point types
> -# aarch64 does not support soft-float, so use hard-float and handle this in code
> -ifdef CONFIG_ARM64
> -CFLAGS_REMOVE_$(AMDDALPATH)/dc/dcn10/dcn10_resource.o := -mgeneral-regs-only
> -endif
> -
> AMD_DISPLAY_FILES += $(AMD_DAL_DCN10)
> diff --git a/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_resource.c b/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_resource.c
> index a78712caf124..462d3d981ea5 100644
> --- a/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_resource.c
> +++ b/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_resource.c
> @@ -1339,47 +1339,6 @@ static uint32_t read_pipe_fuses(struct dc_context *ctx)
> return value;
> }
>
> -/*
> - * Some architectures don't support soft-float (e.g. aarch64), on those
> - * this function has to be called with hardfloat enabled, make sure not
> - * to inline it so whatever fp stuff is done stays inside
> - */
> -static noinline void dcn10_resource_construct_fp(
> - struct dc *dc)
> -{
> - if (dc->ctx->dce_version == DCN_VERSION_1_01) {
> - struct dcn_soc_bounding_box *dcn_soc = dc->dcn_soc;
> - struct dcn_ip_params *dcn_ip = dc->dcn_ip;
> - struct display_mode_lib *dml = &dc->dml;
> -
> - dml->ip.max_num_dpp = 3;
> - /* TODO how to handle 23.84? */
> - dcn_soc->dram_clock_change_latency = 23;
> - dcn_ip->max_num_dpp = 3;
> - }
> - if (ASICREV_IS_RV1_F0(dc->ctx->asic_id.hw_internal_rev)) {
> - dc->dcn_soc->urgent_latency = 3;
> - dc->debug.disable_dmcu = true;
> - dc->dcn_soc->fabric_and_dram_bandwidth_vmax0p9 = 41.60f;
> - }
> -
> -
> - dc->dcn_soc->number_of_channels = dc->ctx->asic_id.vram_width / ddr4_dram_width;
> - ASSERT(dc->dcn_soc->number_of_channels < 3);
> - if (dc->dcn_soc->number_of_channels == 0)/*old sbios bug*/
> - dc->dcn_soc->number_of_channels = 2;
> -
> - if (dc->dcn_soc->number_of_channels == 1) {
> - dc->dcn_soc->fabric_and_dram_bandwidth_vmax0p9 = 19.2f;
> - dc->dcn_soc->fabric_and_dram_bandwidth_vnom0p8 = 17.066f;
> - dc->dcn_soc->fabric_and_dram_bandwidth_vmid0p72 = 14.933f;
> - dc->dcn_soc->fabric_and_dram_bandwidth_vmin0p65 = 12.8f;
> - if (ASICREV_IS_RV1_F0(dc->ctx->asic_id.hw_internal_rev)) {
> - dc->dcn_soc->fabric_and_dram_bandwidth_vmax0p9 = 20.80f;
> - }
> - }
> -}
> -
> static bool dcn10_resource_construct(
> uint8_t num_virtual_links,
> struct dc *dc,
> @@ -1531,15 +1490,37 @@ static bool dcn10_resource_construct(
> memcpy(dc->dcn_ip, &dcn10_ip_defaults, sizeof(dcn10_ip_defaults));
> memcpy(dc->dcn_soc, &dcn10_soc_defaults, sizeof(dcn10_soc_defaults));
>
> -#if defined(CONFIG_ARM64)
> - /* Aarch64 does not support -msoft-float/-mfloat-abi=soft */
> - DC_FP_START();
> - dcn10_resource_construct_fp(dc);
> - DC_FP_END();
> -#else
> - /* Other architectures we build for build this with soft-float */
> - dcn10_resource_construct_fp(dc);
> -#endif
> + if (dc->ctx->dce_version == DCN_VERSION_1_01) {
> + struct dcn_soc_bounding_box *dcn_soc = dc->dcn_soc;
> + struct dcn_ip_params *dcn_ip = dc->dcn_ip;
> + struct display_mode_lib *dml = &dc->dml;
> +
> + dml->ip.max_num_dpp = 3;
> + /* TODO how to handle 23.84? */
> + dcn_soc->dram_clock_change_latency = 23;
> + dcn_ip->max_num_dpp = 3;
> + }
> + if (ASICREV_IS_RV1_F0(dc->ctx->asic_id.hw_internal_rev)) {
> + dc->dcn_soc->urgent_latency = 3;
> + dc->debug.disable_dmcu = true;
> + dc->dcn_soc->fabric_and_dram_bandwidth_vmax0p9 = 41.60f;
> + }
> +
> +
> + dc->dcn_soc->number_of_channels = dc->ctx->asic_id.vram_width / ddr4_dram_width;
> + ASSERT(dc->dcn_soc->number_of_channels < 3);
> + if (dc->dcn_soc->number_of_channels == 0)/*old sbios bug*/
> + dc->dcn_soc->number_of_channels = 2;
> +
> + if (dc->dcn_soc->number_of_channels == 1) {
> + dc->dcn_soc->fabric_and_dram_bandwidth_vmax0p9 = 19.2f;
> + dc->dcn_soc->fabric_and_dram_bandwidth_vnom0p8 = 17.066f;
> + dc->dcn_soc->fabric_and_dram_bandwidth_vmid0p72 = 14.933f;
> + dc->dcn_soc->fabric_and_dram_bandwidth_vmin0p65 = 12.8f;
> + if (ASICREV_IS_RV1_F0(dc->ctx->asic_id.hw_internal_rev)) {
> + dc->dcn_soc->fabric_and_dram_bandwidth_vmax0p9 = 20.80f;
> + }
> + }
>
> pool->base.pp_smu = dcn10_pp_smu_create(ctx);
>
> diff --git a/drivers/gpu/drm/amd/display/dc/dcn20/Makefile b/drivers/gpu/drm/amd/display/dc/dcn20/Makefile
> index 624cb1341ef1..5fcaf78334ff 100644
> --- a/drivers/gpu/drm/amd/display/dc/dcn20/Makefile
> +++ b/drivers/gpu/drm/amd/display/dc/dcn20/Makefile
> @@ -17,10 +17,6 @@ ifdef CONFIG_PPC64
> CFLAGS_$(AMDDALPATH)/dc/dcn20/dcn20_resource.o := -mhard-float -maltivec
> endif
>
> -ifdef CONFIG_ARM64
> -CFLAGS_REMOVE_$(AMDDALPATH)/dc/dcn20/dcn20_resource.o := -mgeneral-regs-only
> -endif
> -
> ifdef CONFIG_CC_IS_GCC
> ifeq ($(call cc-ifversion, -lt, 0701, y), y)
> IS_OLD_GCC = 1
> diff --git a/drivers/gpu/drm/amd/display/dc/dcn21/Makefile b/drivers/gpu/drm/amd/display/dc/dcn21/Makefile
> index 51a2f3d4c194..07684d3e375a 100644
> --- a/drivers/gpu/drm/amd/display/dc/dcn21/Makefile
> +++ b/drivers/gpu/drm/amd/display/dc/dcn21/Makefile
> @@ -13,10 +13,6 @@ ifdef CONFIG_PPC64
> CFLAGS_$(AMDDALPATH)/dc/dcn21/dcn21_resource.o := -mhard-float -maltivec
> endif
>
> -ifdef CONFIG_ARM64
> -CFLAGS_REMOVE_$(AMDDALPATH)/dc/dcn21/dcn21_resource.o := -mgeneral-regs-only
> -endif
> -
> ifdef CONFIG_CC_IS_GCC
> ifeq ($(call cc-ifversion, -lt, 0701, y), y)
> IS_OLD_GCC = 1
> diff --git a/drivers/gpu/drm/amd/display/dc/dml/Makefile b/drivers/gpu/drm/amd/display/dc/dml/Makefile
> index dbc7e2abe379..417331438c30 100644
> --- a/drivers/gpu/drm/amd/display/dc/dml/Makefile
> +++ b/drivers/gpu/drm/amd/display/dc/dml/Makefile
> @@ -33,10 +33,6 @@ ifdef CONFIG_PPC64
> dml_ccflags := -mhard-float -maltivec
> endif
>
> -ifdef CONFIG_ARM64
> -dml_rcflags := -mgeneral-regs-only
> -endif
> -
> ifdef CONFIG_CC_IS_GCC
> ifeq ($(call cc-ifversion, -lt, 0701, y), y)
> IS_OLD_GCC = 1
> @@ -64,13 +60,6 @@ CFLAGS_$(AMDDALPATH)/dc/dml/dcn20/display_mode_vba_20v2.o := $(dml_ccflags)
> CFLAGS_$(AMDDALPATH)/dc/dml/dcn20/display_rq_dlg_calc_20v2.o := $(dml_ccflags)
> CFLAGS_$(AMDDALPATH)/dc/dml/dcn21/display_mode_vba_21.o := $(dml_ccflags)
> CFLAGS_$(AMDDALPATH)/dc/dml/dcn21/display_rq_dlg_calc_21.o := $(dml_ccflags)
> -CFLAGS_REMOVE_$(AMDDALPATH)/dc/dml/display_mode_vba.o := $(dml_rcflags)
> -CFLAGS_REMOVE_$(AMDDALPATH)/dc/dml/dcn20/display_mode_vba_20.o := $(dml_rcflags)
> -CFLAGS_REMOVE_$(AMDDALPATH)/dc/dml/dcn20/display_rq_dlg_calc_20.o := $(dml_rcflags)
> -CFLAGS_REMOVE_$(AMDDALPATH)/dc/dml/dcn20/display_mode_vba_20v2.o := $(dml_rcflags)
> -CFLAGS_REMOVE_$(AMDDALPATH)/dc/dml/dcn20/display_rq_dlg_calc_20v2.o := $(dml_rcflags)
> -CFLAGS_REMOVE_$(AMDDALPATH)/dc/dml/dcn21/display_mode_vba_21.o := $(dml_rcflags)
> -CFLAGS_REMOVE_$(AMDDALPATH)/dc/dml/dcn21/display_rq_dlg_calc_21.o := $(dml_rcflags)
> endif
> ifdef CONFIG_DRM_AMD_DC_DCN3_0
> CFLAGS_$(AMDDALPATH)/dc/dml/dcn30/display_mode_vba_30.o := $(dml_ccflags) -Wframe-larger-than=2048
> @@ -78,8 +67,6 @@ CFLAGS_$(AMDDALPATH)/dc/dml/dcn30/display_rq_dlg_calc_30.o := $(dml_ccflags)
> endif
> CFLAGS_$(AMDDALPATH)/dc/dml/dml1_display_rq_dlg_calc.o := $(dml_ccflags)
> CFLAGS_$(AMDDALPATH)/dc/dml/display_rq_dlg_helpers.o := $(dml_ccflags)
> -CFLAGS_REMOVE_$(AMDDALPATH)/dc/dml/dml1_display_rq_dlg_calc.o := $(dml_rcflags)
> -CFLAGS_REMOVE_$(AMDDALPATH)/dc/dml/display_rq_dlg_helpers.o := $(dml_rcflags)
>
> DML = display_mode_lib.o display_rq_dlg_helpers.o dml1_display_rq_dlg_calc.o \
>
> diff --git a/drivers/gpu/drm/amd/display/dc/dsc/Makefile b/drivers/gpu/drm/amd/display/dc/dsc/Makefile
> index f2624a1156e5..ea29cf95d470 100644
> --- a/drivers/gpu/drm/amd/display/dc/dsc/Makefile
> +++ b/drivers/gpu/drm/amd/display/dc/dsc/Makefile
> @@ -10,10 +10,6 @@ ifdef CONFIG_PPC64
> dsc_ccflags := -mhard-float -maltivec
> endif
>
> -ifdef CONFIG_ARM64
> -dsc_rcflags := -mgeneral-regs-only
> -endif
> -
> ifdef CONFIG_CC_IS_GCC
> ifeq ($(call cc-ifversion, -lt, 0701, y), y)
> IS_OLD_GCC = 1
> @@ -32,7 +28,6 @@ endif
> endif
>
> CFLAGS_$(AMDDALPATH)/dc/dsc/rc_calc.o := $(dsc_ccflags)
> -CFLAGS_REMOVE_$(AMDDALPATH)/dc/dsc/rc_calc.o := $(dsc_rcflags)
>
> DSC = dc_dsc.o rc_calc.o rc_calc_dpi.o
>
> diff --git a/drivers/gpu/drm/amd/display/dc/os_types.h b/drivers/gpu/drm/amd/display/dc/os_types.h
> index 95cb56929e79..126c2f3a4dd3 100644
> --- a/drivers/gpu/drm/amd/display/dc/os_types.h
> +++ b/drivers/gpu/drm/amd/display/dc/os_types.h
> @@ -55,10 +55,6 @@
> #include <asm/fpu/api.h>
> #define DC_FP_START() kernel_fpu_begin()
> #define DC_FP_END() kernel_fpu_end()
> -#elif defined(CONFIG_ARM64)
> -#include <asm/neon.h>
> -#define DC_FP_START() kernel_neon_begin()
> -#define DC_FP_END() kernel_neon_end()
> #elif defined(CONFIG_PPC64)
> #include <asm/switch_to.h>
> #include <asm/cputable.h>
>