[PATCH v2 0/4] drm/amd/display: Base changes for isolating FPU operation in a single place

[PATCH v2 0/4] drm/amd/display: Base changes for isolating FPU operation in a single place

[Rodrigo Siqueira]

Hi,

In the display core, we utilize floats and doubles units for calculating
modesetting parameters. One side effect of our approach to use double-precision
is the fact that we spread multiple FPU access across our driver, which means
that we can accidentally clobber user space FPU state.

# Challenges

1. Keep in mind that this FPU code is ingrained in our display driver and
performs several crucial tasks. Additionally, we already have multiple
architectures available in the kernel and a large set of users; in other words,
we prefer to avoid a radical approach that might break our user's system.

2. We share our display code with other OSs; thus, we need to maintain the
interoperability between these two systems.

3. We need a mechanism for identifying which function uses FPU registers;
fortunately, Peter Zijlstra wrote a series a couple of months ago where he
introduced an FPU check for objtool. I used the following command for
identifying the potential FPU usage:

 ./tools/objtool/objtool check -Ffa "drivers/gpu/drm/amd/display/dc/ANY_FILE.o"

4. Since our code heavily relies on FPU and the fact that we spread
kernel_fpu_begin/end across multiple functions, we can have some complex
scenarios that will require code refactoring. However, we want to avoid
complicated changes since this is a formula to introduce regressions; we want
something that allows us to fix it in small, safe, and reliable steps.

5. Unfortunately, for legacy reasons, we have some problems in how we program
our FPU access, which in some weird scenarios can generate situations where we
try to enter in the fpu mode multiple times or exit too early.

# Our approach

For trying to solve this problem, we came up with the following strategy:

1. Keep in mind that we are using kernel_fpu_begin/end spread in various areas
and sometimes across multiple functions. If we try to move some of the
functions to an isolated place, we can generate a situation where we can call
the FPU protection more than once, causing multiple warnings. We can deal with
this problem by adding a thin management layer around the kernel_fpu_begin/end
used inside the display.

2. We will need a trace mechanism for this FPU management inside our display
code.

3. After we get the thin layer that manages FPU, we can start to move each
function that uses FPU to a centralized place. Our DQE runs multiple tests in
different ASICs every week; we can take advantage of this to ensure that our
FPU patches work does not introduce any regression. The idea is to work on a
specific part of the code every week (e.g., week 1: DCN2, week 1: DCN2.1,
etc.).

4. Finally, after we can isolate the FPU operations in a single place, we can
altogether remove the FPU flags from other files and eliminate an unnecessary
code introduced to deal with this problem. We can also remove the thin layer
added in the step 3.

# This series

To maintain the interoperability between multiple OSes, we already have a
define named DC_FP_START/END, which is a straightforward wrapper to
kernel_fpu_begin/end in the Linux side. In this series, I decided to expand the
scope of this DC_FP_* wrapper to trace FPU entrance and exit in the display
code, but I also add a mechanism for managing the entrance and exit of
kernel_fpu_begin/end. You can see the details on how I did that in the last two
patches.

I also isolate a simple function that requires FPU access to demonstrate my
strategy for isolating this FPU access in a single place. If this series gets
accepted, the following steps consist of moving all FPU functions weekly until
we isolate everything in the fpu_operation folder.

Changes since V1:
- Use a better name for variables.
- Update documentation.
- Avoid preemption.

* See update details per commit message

Best Regards
Rodrigo Siqueira

Rodrigo Siqueira (4):
  drm/amd/display: Introduce FPU directory inside DC
  drm/amd/display: Add FPU event trace
  drm/amd/display: Add control mechanism for FPU utilization
  drm/amd/display: Add DC_FP helper to check FPU state

 .../gpu/drm/amd/display/amdgpu_dm/Makefile    |   3 +-
 .../amd/display/amdgpu_dm/amdgpu_dm_trace.h   |  24 ++++
 .../gpu/drm/amd/display/amdgpu_dm/dc_fpu.c    | 114 ++++++++++++++++++
 .../gpu/drm/amd/display/amdgpu_dm/dc_fpu.h    |  34 ++++++
 drivers/gpu/drm/amd/display/dc/Makefile       |   1 +
 drivers/gpu/drm/amd/display/dc/dc_trace.h     |   3 +
 .../drm/amd/display/dc/dcn20/dcn20_resource.c |  41 +------
 .../drm/amd/display/dc/dcn20/dcn20_resource.h |   2 -
 .../drm/amd/display/dc/dcn21/dcn21_resource.c |   2 +
 .../amd/display/dc/fpu_operations/Makefile    |  58 +++++++++
 .../drm/amd/display/dc/fpu_operations/dcn2x.c | 104 ++++++++++++++++
 .../drm/amd/display/dc/fpu_operations/dcn2x.h |  33 +++++
 drivers/gpu/drm/amd/display/dc/os_types.h     |   6 +-
 13 files changed, 382 insertions(+), 43 deletions(-)
 create mode 100644 drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c
 create mode 100644 drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.h
 create mode 100644 drivers/gpu/drm/amd/display/dc/fpu_operations/Makefile
 create mode 100644 drivers/gpu/drm/amd/display/dc/fpu_operations/dcn2x.c
 create mode 100644 drivers/gpu/drm/amd/display/dc/fpu_operations/dcn2x.h

-- 
2.25.1

[PATCH v2 1/4] drm/amd/display: Introduce FPU directory inside DC

[Rodrigo Siqueira]

The display core files rely on FPU operation, which requires to be
compiled with special flags. Ideally, we don't want these FPU operations
spread around the DC code; nevertheless, it happens in the current
source. This commit introduces a new directory named fpu_operations that
intends to centralize all files that require the FPU compilation flag.
As part of this new component, this patch also moves one of the
functions that require FPU access to a single shared file. Notice that
this is the first part of the work, and it does not fix the FPU issue
yet; we still need other patches for achieving the complete isolation of
this file.

Change since V1:
- Update documentation and rebase.

Signed-off-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
---
 drivers/gpu/drm/amd/display/dc/Makefile       |  1 +
 .../drm/amd/display/dc/dcn20/dcn20_resource.c | 39 +--------
 .../drm/amd/display/dc/dcn20/dcn20_resource.h |  2 -
 .../drm/amd/display/dc/dcn21/dcn21_resource.c |  2 +
 .../amd/display/dc/fpu_operations/Makefile    | 58 +++++++++++++
 .../drm/amd/display/dc/fpu_operations/dcn2x.c | 87 +++++++++++++++++++
 .../drm/amd/display/dc/fpu_operations/dcn2x.h | 33 +++++++
 7 files changed, 183 insertions(+), 39 deletions(-)
 create mode 100644 drivers/gpu/drm/amd/display/dc/fpu_operations/Makefile
 create mode 100644 drivers/gpu/drm/amd/display/dc/fpu_operations/dcn2x.c
 create mode 100644 drivers/gpu/drm/amd/display/dc/fpu_operations/dcn2x.h

diff --git a/drivers/gpu/drm/amd/display/dc/Makefile b/drivers/gpu/drm/amd/display/dc/Makefile
index 943fcb164876..93e731a9be68 100644
--- a/drivers/gpu/drm/amd/display/dc/Makefile
+++ b/drivers/gpu/drm/amd/display/dc/Makefile
@@ -37,6 +37,7 @@ DC_LIBS += dcn303
 DC_LIBS += dcn31
 endif
 
+DC_LIBS += fpu_operations
 DC_LIBS += dce120
 
 DC_LIBS += dce112
diff --git a/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c b/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c
index 1b05a37b674d..f99b09643a52 100644
--- a/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c
+++ b/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c
@@ -35,6 +35,8 @@
 #include "include/irq_service_interface.h"
 #include "dcn20/dcn20_resource.h"
 
+#include "fpu_operations/dcn2x.h"
+
 #include "dcn10/dcn10_hubp.h"
 #include "dcn10/dcn10_ipp.h"
 #include "dcn20_hubbub.h"
@@ -1974,43 +1976,6 @@ void dcn20_split_stream_for_mpc(
 	ASSERT(primary_pipe->plane_state);
 }
 
-void dcn20_populate_dml_writeback_from_context(
-		struct dc *dc, struct resource_context *res_ctx, display_e2e_pipe_params_st *pipes)
-{
-	int pipe_cnt, i;
-
-	for (i = 0, pipe_cnt = 0; i < dc->res_pool->pipe_count; i++) {
-		struct dc_writeback_info *wb_info = &res_ctx->pipe_ctx[i].stream->writeback_info[0];
-
-		if (!res_ctx->pipe_ctx[i].stream)
-			continue;
-
-		/* Set writeback information */
-		pipes[pipe_cnt].dout.wb_enable = (wb_info->wb_enabled == true) ? 1 : 0;
-		pipes[pipe_cnt].dout.num_active_wb++;
-		pipes[pipe_cnt].dout.wb.wb_src_height = wb_info->dwb_params.cnv_params.crop_height;
-		pipes[pipe_cnt].dout.wb.wb_src_width = wb_info->dwb_params.cnv_params.crop_width;
-		pipes[pipe_cnt].dout.wb.wb_dst_width = wb_info->dwb_params.dest_width;
-		pipes[pipe_cnt].dout.wb.wb_dst_height = wb_info->dwb_params.dest_height;
-		pipes[pipe_cnt].dout.wb.wb_htaps_luma = 1;
-		pipes[pipe_cnt].dout.wb.wb_vtaps_luma = 1;
-		pipes[pipe_cnt].dout.wb.wb_htaps_chroma = wb_info->dwb_params.scaler_taps.h_taps_c;
-		pipes[pipe_cnt].dout.wb.wb_vtaps_chroma = wb_info->dwb_params.scaler_taps.v_taps_c;
-		pipes[pipe_cnt].dout.wb.wb_hratio = 1.0;
-		pipes[pipe_cnt].dout.wb.wb_vratio = 1.0;
-		if (wb_info->dwb_params.out_format == dwb_scaler_mode_yuv420) {
-			if (wb_info->dwb_params.output_depth == DWB_OUTPUT_PIXEL_DEPTH_8BPC)
-				pipes[pipe_cnt].dout.wb.wb_pixel_format = dm_420_8;
-			else
-				pipes[pipe_cnt].dout.wb.wb_pixel_format = dm_420_10;
-		} else
-			pipes[pipe_cnt].dout.wb.wb_pixel_format = dm_444_32;
-
-		pipe_cnt++;
-	}
-
-}
-
 int dcn20_populate_dml_pipes_from_context(
 		struct dc *dc,
 		struct dc_state *context,
diff --git a/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.h b/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.h
index c8f3127bbcdf..6ec8ff45f0f7 100644
--- a/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.h
+++ b/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.h
@@ -58,8 +58,6 @@ struct pipe_ctx *dcn20_acquire_idle_pipe_for_layer(
 		struct dc_state *state,
 		const struct resource_pool *pool,
 		struct dc_stream_state *stream);
-void dcn20_populate_dml_writeback_from_context(
-		struct dc *dc, struct resource_context *res_ctx, display_e2e_pipe_params_st *pipes);
 
 struct stream_encoder *dcn20_stream_encoder_create(
 	enum engine_id eng_id,
diff --git a/drivers/gpu/drm/amd/display/dc/dcn21/dcn21_resource.c b/drivers/gpu/drm/amd/display/dc/dcn21/dcn21_resource.c
index f3d98e3ba624..85385144e2c5 100644
--- a/drivers/gpu/drm/amd/display/dc/dcn21/dcn21_resource.c
+++ b/drivers/gpu/drm/amd/display/dc/dcn21/dcn21_resource.c
@@ -35,6 +35,8 @@
 #include "include/irq_service_interface.h"
 #include "dcn20/dcn20_resource.h"
 
+#include "fpu_operations/dcn2x.h"
+
 #include "clk_mgr.h"
 #include "dcn10/dcn10_hubp.h"
 #include "dcn10/dcn10_ipp.h"
diff --git a/drivers/gpu/drm/amd/display/dc/fpu_operations/Makefile b/drivers/gpu/drm/amd/display/dc/fpu_operations/Makefile
new file mode 100644
index 000000000000..7f6f90c3f267
--- /dev/null
+++ b/drivers/gpu/drm/amd/display/dc/fpu_operations/Makefile
@@ -0,0 +1,58 @@
+# SPDX-License-Identifier: MIT
+#
+# Copyright 2021 Advanced Micro Devices, Inc.
+#
+# Permission is hereby granted, free of charge, to any person obtaining a
+# copy of this software and associated documentation files (the "Software"),
+# to deal in the Software without restriction, including without limitation
+# the rights to use, copy, modify, merge, publish, distribute, sublicense,
+# and/or sell copies of the Software, and to permit persons to whom the
+# Software is furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+# THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
+# OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+# ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+# OTHER DEALINGS IN THE SOFTWARE.
+#
+#
+# Makefile for fpu operations component.
+#
+
+FPU_OPERATIONS = dcn2x.o
+
+ifdef CONFIG_X86
+fpu_ccflags := -mhard-float -msse
+endif
+
+ifdef CONFIG_PPC64
+fpu_ccflags := -mhard-float -maltivec
+endif
+
+ifdef CONFIG_CC_IS_GCC
+ifeq ($(call cc-ifversion, -lt, 0701, y), y)
+IS_OLD_GCC = 1
+endif
+endif
+
+ifdef CONFIG_X86
+ifdef IS_OLD_GCC
+# Stack alignment mismatch, proceed with caution.
+# GCC < 7.1 cannot compile code using `double` and -mpreferred-stack-boundary=3
+# (8B stack alignment).
+fpu_ccflags := -mpreferred-stack-boundary=4
+else
+fpu_ccflags :=  -msse2
+endif
+endif
+
+CFLAGS_$(AMDDALPATH)/dc/fpu_operations/dcn2x.o += $(fpu_ccflags)
+
+AMD_DAL_FPU_OPERATIONS = $(addprefix $(AMDDALPATH)/dc/fpu_operations/,$(FPU_OPERATIONS))
+
+AMD_DISPLAY_FILES += $(AMD_DAL_FPU_OPERATIONS)
diff --git a/drivers/gpu/drm/amd/display/dc/fpu_operations/dcn2x.c b/drivers/gpu/drm/amd/display/dc/fpu_operations/dcn2x.c
new file mode 100644
index 000000000000..c815d6c01d64
--- /dev/null
+++ b/drivers/gpu/drm/amd/display/dc/fpu_operations/dcn2x.c
@@ -0,0 +1,87 @@
+// SPDX-License-Identifier: MIT
+/*
+ * Copyright 2021 Advanced Micro Devices, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
+ * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+ * OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * Authors: AMD
+ *
+ */
+
+#include "resource.h"
+
+/**
+ * DOC: DCN2x FPU manipulation Overview
+ *
+ * The DCN architecture relies on FPU operations, which require special
+ * compilation flags and the use of kernel_fpu_begin/end functions; ideally, we
+ * want to avoid spreading FPU access across multiple files. With this idea in
+ * mind, this file aims to centralize all DCN20 and DCN2.1 (DCN2x) functions
+ * that require FPU access in a single place. Code in this file follows the
+ * following code pattern:
+ *
+ * 1. Functions that use FPU operations should be isolated in static functions.
+ * 2. The FPU functions should have the noinline attribute to ensure anything
+ *    that deals with FP register is contained within this call.
+ * 3. All function that needs to be accessed outside this file requires a
+ *    public interface that not uses any FPU reference.
+ */
+
+static noinline void _dcn20_populate_dml_writeback_from_context(struct dc *dc,
+	struct resource_context *res_ctx, display_e2e_pipe_params_st *pipes)
+{
+	int pipe_cnt, i;
+
+	for (i = 0, pipe_cnt = 0; i < dc->res_pool->pipe_count; i++) {
+		struct dc_writeback_info *wb_info = &res_ctx->pipe_ctx[i].stream->writeback_info[0];
+
+		if (!res_ctx->pipe_ctx[i].stream)
+			continue;
+
+		/* Set writeback information */
+		pipes[pipe_cnt].dout.wb_enable = (wb_info->wb_enabled == true) ? 1 : 0;
+		pipes[pipe_cnt].dout.num_active_wb++;
+		pipes[pipe_cnt].dout.wb.wb_src_height = wb_info->dwb_params.cnv_params.crop_height;
+		pipes[pipe_cnt].dout.wb.wb_src_width = wb_info->dwb_params.cnv_params.crop_width;
+		pipes[pipe_cnt].dout.wb.wb_dst_width = wb_info->dwb_params.dest_width;
+		pipes[pipe_cnt].dout.wb.wb_dst_height = wb_info->dwb_params.dest_height;
+		pipes[pipe_cnt].dout.wb.wb_htaps_luma = 1;
+		pipes[pipe_cnt].dout.wb.wb_vtaps_luma = 1;
+		pipes[pipe_cnt].dout.wb.wb_htaps_chroma = wb_info->dwb_params.scaler_taps.h_taps_c;
+		pipes[pipe_cnt].dout.wb.wb_vtaps_chroma = wb_info->dwb_params.scaler_taps.v_taps_c;
+		pipes[pipe_cnt].dout.wb.wb_hratio = 1.0;
+		pipes[pipe_cnt].dout.wb.wb_vratio = 1.0;
+		if (wb_info->dwb_params.out_format == dwb_scaler_mode_yuv420) {
+			if (wb_info->dwb_params.output_depth == DWB_OUTPUT_PIXEL_DEPTH_8BPC)
+				pipes[pipe_cnt].dout.wb.wb_pixel_format = dm_420_8;
+			else
+				pipes[pipe_cnt].dout.wb.wb_pixel_format = dm_420_10;
+		} else {
+			pipes[pipe_cnt].dout.wb.wb_pixel_format = dm_444_32;
+		}
+
+		pipe_cnt++;
+	}
+}
+
+void dcn20_populate_dml_writeback_from_context(struct dc *dc,
+	struct resource_context *res_ctx, display_e2e_pipe_params_st *pipes)
+{
+	_dcn20_populate_dml_writeback_from_context(dc, res_ctx, pipes);
+}
diff --git a/drivers/gpu/drm/amd/display/dc/fpu_operations/dcn2x.h b/drivers/gpu/drm/amd/display/dc/fpu_operations/dcn2x.h
new file mode 100644
index 000000000000..c060f909164b
--- /dev/null
+++ b/drivers/gpu/drm/amd/display/dc/fpu_operations/dcn2x.h
@@ -0,0 +1,33 @@
+/* SPDX-License-Identifier: MIT */
+/*
+ * Copyright 2021 Advanced Micro Devices, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
+ * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+ * OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * Authors: AMD
+ *
+ */
+
+#ifndef __DCN2X_H__
+#define __DCN2X_H__
+
+void dcn20_populate_dml_writeback_from_context(struct dc *dc,
+	struct resource_context *res_ctx, display_e2e_pipe_params_st *pipes);
+
+#endif /* __DCN2X_H__ */
-- 
2.25.1

Re: [PATCH v2 1/4] drm/amd/display: Introduce FPU directory inside DC

[Christian König]

Am 13.07.21 um 16:06 schrieb Rodrigo Siqueira:
> The display core files rely on FPU operation, which requires to be
> compiled with special flags. Ideally, we don't want these FPU operations
> spread around the DC code; nevertheless, it happens in the current
> source. This commit introduces a new directory named fpu_operations that
> intends to centralize all files that require the FPU compilation flag.
> As part of this new component, this patch also moves one of the
> functions that require FPU access to a single shared file. Notice that
> this is the first part of the work, and it does not fix the FPU issue
> yet; we still need other patches for achieving the complete isolation of
> this file.
>
> Change since V1:
> - Update documentation and rebase.
>
> Signed-off-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
> ---
>   drivers/gpu/drm/amd/display/dc/Makefile       |  1 +
>   .../drm/amd/display/dc/dcn20/dcn20_resource.c | 39 +--------
>   .../drm/amd/display/dc/dcn20/dcn20_resource.h |  2 -
>   .../drm/amd/display/dc/dcn21/dcn21_resource.c |  2 +
>   .../amd/display/dc/fpu_operations/Makefile    | 58 +++++++++++++
>   .../drm/amd/display/dc/fpu_operations/dcn2x.c | 87 +++++++++++++++++++
>   .../drm/amd/display/dc/fpu_operations/dcn2x.h | 33 +++++++
>   7 files changed, 183 insertions(+), 39 deletions(-)
>   create mode 100644 drivers/gpu/drm/amd/display/dc/fpu_operations/Makefile
>   create mode 100644 drivers/gpu/drm/amd/display/dc/fpu_operations/dcn2x.c
>   create mode 100644 drivers/gpu/drm/amd/display/dc/fpu_operations/dcn2x.h
>
> diff --git a/drivers/gpu/drm/amd/display/dc/Makefile b/drivers/gpu/drm/amd/display/dc/Makefile
> index 943fcb164876..93e731a9be68 100644
> --- a/drivers/gpu/drm/amd/display/dc/Makefile
> +++ b/drivers/gpu/drm/amd/display/dc/Makefile
> @@ -37,6 +37,7 @@ DC_LIBS += dcn303
>   DC_LIBS += dcn31
>   endif
>   
> +DC_LIBS += fpu_operations
>   DC_LIBS += dce120
>   
>   DC_LIBS += dce112
> diff --git a/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c b/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c
> index 1b05a37b674d..f99b09643a52 100644
> --- a/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c
> +++ b/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c
> @@ -35,6 +35,8 @@
>   #include "include/irq_service_interface.h"
>   #include "dcn20/dcn20_resource.h"
>   
> +#include "fpu_operations/dcn2x.h"
> +
>   #include "dcn10/dcn10_hubp.h"
>   #include "dcn10/dcn10_ipp.h"
>   #include "dcn20_hubbub.h"
> @@ -1974,43 +1976,6 @@ void dcn20_split_stream_for_mpc(
>   	ASSERT(primary_pipe->plane_state);
>   }
>   
> -void dcn20_populate_dml_writeback_from_context(
> -		struct dc *dc, struct resource_context *res_ctx, display_e2e_pipe_params_st *pipes)
> -{
> -	int pipe_cnt, i;
> -
> -	for (i = 0, pipe_cnt = 0; i < dc->res_pool->pipe_count; i++) {
> -		struct dc_writeback_info *wb_info = &res_ctx->pipe_ctx[i].stream->writeback_info[0];
> -
> -		if (!res_ctx->pipe_ctx[i].stream)
> -			continue;
> -
> -		/* Set writeback information */
> -		pipes[pipe_cnt].dout.wb_enable = (wb_info->wb_enabled == true) ? 1 : 0;
> -		pipes[pipe_cnt].dout.num_active_wb++;
> -		pipes[pipe_cnt].dout.wb.wb_src_height = wb_info->dwb_params.cnv_params.crop_height;
> -		pipes[pipe_cnt].dout.wb.wb_src_width = wb_info->dwb_params.cnv_params.crop_width;
> -		pipes[pipe_cnt].dout.wb.wb_dst_width = wb_info->dwb_params.dest_width;
> -		pipes[pipe_cnt].dout.wb.wb_dst_height = wb_info->dwb_params.dest_height;
> -		pipes[pipe_cnt].dout.wb.wb_htaps_luma = 1;
> -		pipes[pipe_cnt].dout.wb.wb_vtaps_luma = 1;
> -		pipes[pipe_cnt].dout.wb.wb_htaps_chroma = wb_info->dwb_params.scaler_taps.h_taps_c;
> -		pipes[pipe_cnt].dout.wb.wb_vtaps_chroma = wb_info->dwb_params.scaler_taps.v_taps_c;
> -		pipes[pipe_cnt].dout.wb.wb_hratio = 1.0;
> -		pipes[pipe_cnt].dout.wb.wb_vratio = 1.0;
> -		if (wb_info->dwb_params.out_format == dwb_scaler_mode_yuv420) {
> -			if (wb_info->dwb_params.output_depth == DWB_OUTPUT_PIXEL_DEPTH_8BPC)
> -				pipes[pipe_cnt].dout.wb.wb_pixel_format = dm_420_8;
> -			else
> -				pipes[pipe_cnt].dout.wb.wb_pixel_format = dm_420_10;
> -		} else
> -			pipes[pipe_cnt].dout.wb.wb_pixel_format = dm_444_32;
> -
> -		pipe_cnt++;
> -	}
> -
> -}
> -
>   int dcn20_populate_dml_pipes_from_context(
>   		struct dc *dc,
>   		struct dc_state *context,
> diff --git a/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.h b/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.h
> index c8f3127bbcdf..6ec8ff45f0f7 100644
> --- a/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.h
> +++ b/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.h
> @@ -58,8 +58,6 @@ struct pipe_ctx *dcn20_acquire_idle_pipe_for_layer(
>   		struct dc_state *state,
>   		const struct resource_pool *pool,
>   		struct dc_stream_state *stream);
> -void dcn20_populate_dml_writeback_from_context(
> -		struct dc *dc, struct resource_context *res_ctx, display_e2e_pipe_params_st *pipes);
>   
>   struct stream_encoder *dcn20_stream_encoder_create(
>   	enum engine_id eng_id,
> diff --git a/drivers/gpu/drm/amd/display/dc/dcn21/dcn21_resource.c b/drivers/gpu/drm/amd/display/dc/dcn21/dcn21_resource.c
> index f3d98e3ba624..85385144e2c5 100644
> --- a/drivers/gpu/drm/amd/display/dc/dcn21/dcn21_resource.c
> +++ b/drivers/gpu/drm/amd/display/dc/dcn21/dcn21_resource.c
> @@ -35,6 +35,8 @@
>   #include "include/irq_service_interface.h"
>   #include "dcn20/dcn20_resource.h"
>   
> +#include "fpu_operations/dcn2x.h"
> +
>   #include "clk_mgr.h"
>   #include "dcn10/dcn10_hubp.h"
>   #include "dcn10/dcn10_ipp.h"
> diff --git a/drivers/gpu/drm/amd/display/dc/fpu_operations/Makefile b/drivers/gpu/drm/amd/display/dc/fpu_operations/Makefile
> new file mode 100644
> index 000000000000..7f6f90c3f267
> --- /dev/null
> +++ b/drivers/gpu/drm/amd/display/dc/fpu_operations/Makefile
> @@ -0,0 +1,58 @@
> +# SPDX-License-Identifier: MIT
> +#
> +# Copyright 2021 Advanced Micro Devices, Inc.
> +#
> +# Permission is hereby granted, free of charge, to any person obtaining a
> +# copy of this software and associated documentation files (the "Software"),
> +# to deal in the Software without restriction, including without limitation
> +# the rights to use, copy, modify, merge, publish, distribute, sublicense,
> +# and/or sell copies of the Software, and to permit persons to whom the
> +# Software is furnished to do so, subject to the following conditions:
> +#
> +# The above copyright notice and this permission notice shall be included in
> +# all copies or substantial portions of the Software.
> +#
> +# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> +# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> +# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
> +# THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
> +# OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
> +# ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
> +# OTHER DEALINGS IN THE SOFTWARE.
> +#
> +#
> +# Makefile for fpu operations component.
> +#
> +
> +FPU_OPERATIONS = dcn2x.o
> +
> +ifdef CONFIG_X86
> +fpu_ccflags := -mhard-float -msse
> +endif
> +
> +ifdef CONFIG_PPC64
> +fpu_ccflags := -mhard-float -maltivec
> +endif
> +
> +ifdef CONFIG_CC_IS_GCC
> +ifeq ($(call cc-ifversion, -lt, 0701, y), y)
> +IS_OLD_GCC = 1
> +endif
> +endif
> +
> +ifdef CONFIG_X86
> +ifdef IS_OLD_GCC
> +# Stack alignment mismatch, proceed with caution.
> +# GCC < 7.1 cannot compile code using `double` and -mpreferred-stack-boundary=3
> +# (8B stack alignment).
> +fpu_ccflags := -mpreferred-stack-boundary=4
> +else
> +fpu_ccflags :=  -msse2
> +endif
> +endif
> +
> +CFLAGS_$(AMDDALPATH)/dc/fpu_operations/dcn2x.o += $(fpu_ccflags)
> +
> +AMD_DAL_FPU_OPERATIONS = $(addprefix $(AMDDALPATH)/dc/fpu_operations/,$(FPU_OPERATIONS))
> +
> +AMD_DISPLAY_FILES += $(AMD_DAL_FPU_OPERATIONS)
> diff --git a/drivers/gpu/drm/amd/display/dc/fpu_operations/dcn2x.c b/drivers/gpu/drm/amd/display/dc/fpu_operations/dcn2x.c
> new file mode 100644
> index 000000000000..c815d6c01d64
> --- /dev/null
> +++ b/drivers/gpu/drm/amd/display/dc/fpu_operations/dcn2x.c
> @@ -0,0 +1,87 @@
> +// SPDX-License-Identifier: MIT
> +/*
> + * Copyright 2021 Advanced Micro Devices, Inc.
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a
> + * copy of this software and associated documentation files (the "Software"),
> + * to deal in the Software without restriction, including without limitation
> + * the rights to use, copy, modify, merge, publish, distribute, sublicense,
> + * and/or sell copies of the Software, and to permit persons to whom the
> + * Software is furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice shall be included in
> + * all copies or substantial portions of the Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
> + * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
> + * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
> + * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
> + * OTHER DEALINGS IN THE SOFTWARE.
> + *
> + * Authors: AMD
> + *
> + */
> +
> +#include "resource.h"
> +
> +/**
> + * DOC: DCN2x FPU manipulation Overview
> + *
> + * The DCN architecture relies on FPU operations, which require special
> + * compilation flags and the use of kernel_fpu_begin/end functions; ideally, we
> + * want to avoid spreading FPU access across multiple files. With this idea in
> + * mind, this file aims to centralize all DCN20 and DCN2.1 (DCN2x) functions
> + * that require FPU access in a single place. Code in this file follows the
> + * following code pattern:
> + *
> + * 1. Functions that use FPU operations should be isolated in static functions.
> + * 2. The FPU functions should have the noinline attribute to ensure anything
> + *    that deals with FP register is contained within this call.
> + * 3. All function that needs to be accessed outside this file requires a
> + *    public interface that not uses any FPU reference.
> + */
> +
> +static noinline void _dcn20_populate_dml_writeback_from_context(struct dc *dc,
> +	struct resource_context *res_ctx, display_e2e_pipe_params_st *pipes)
> +{
> +	int pipe_cnt, i;
> +
> +	for (i = 0, pipe_cnt = 0; i < dc->res_pool->pipe_count; i++) {
> +		struct dc_writeback_info *wb_info = &res_ctx->pipe_ctx[i].stream->writeback_info[0];
> +
> +		if (!res_ctx->pipe_ctx[i].stream)
> +			continue;
> +
> +		/* Set writeback information */
> +		pipes[pipe_cnt].dout.wb_enable = (wb_info->wb_enabled == true) ? 1 : 0;
> +		pipes[pipe_cnt].dout.num_active_wb++;
> +		pipes[pipe_cnt].dout.wb.wb_src_height = wb_info->dwb_params.cnv_params.crop_height;
> +		pipes[pipe_cnt].dout.wb.wb_src_width = wb_info->dwb_params.cnv_params.crop_width;
> +		pipes[pipe_cnt].dout.wb.wb_dst_width = wb_info->dwb_params.dest_width;
> +		pipes[pipe_cnt].dout.wb.wb_dst_height = wb_info->dwb_params.dest_height;
> +		pipes[pipe_cnt].dout.wb.wb_htaps_luma = 1;
> +		pipes[pipe_cnt].dout.wb.wb_vtaps_luma = 1;
> +		pipes[pipe_cnt].dout.wb.wb_htaps_chroma = wb_info->dwb_params.scaler_taps.h_taps_c;
> +		pipes[pipe_cnt].dout.wb.wb_vtaps_chroma = wb_info->dwb_params.scaler_taps.v_taps_c;
> +		pipes[pipe_cnt].dout.wb.wb_hratio = 1.0;
> +		pipes[pipe_cnt].dout.wb.wb_vratio = 1.0;
> +		if (wb_info->dwb_params.out_format == dwb_scaler_mode_yuv420) {
> +			if (wb_info->dwb_params.output_depth == DWB_OUTPUT_PIXEL_DEPTH_8BPC)
> +				pipes[pipe_cnt].dout.wb.wb_pixel_format = dm_420_8;
> +			else
> +				pipes[pipe_cnt].dout.wb.wb_pixel_format = dm_420_10;
> +		} else {
> +			pipes[pipe_cnt].dout.wb.wb_pixel_format = dm_444_32;
> +		}
> +
> +		pipe_cnt++;
> +	}
> +}
> +
> +void dcn20_populate_dml_writeback_from_context(struct dc *dc,
> +	struct resource_context *res_ctx, display_e2e_pipe_params_st *pipes)
> +{
> +	_dcn20_populate_dml_writeback_from_context(dc, res_ctx, pipes);
> +}

As far as I can see you don't need the wrapper function any longer.

Just put the implementation in this function directly.

Christian.

> diff --git a/drivers/gpu/drm/amd/display/dc/fpu_operations/dcn2x.h b/drivers/gpu/drm/amd/display/dc/fpu_operations/dcn2x.h
> new file mode 100644
> index 000000000000..c060f909164b
> --- /dev/null
> +++ b/drivers/gpu/drm/amd/display/dc/fpu_operations/dcn2x.h
> @@ -0,0 +1,33 @@
> +/* SPDX-License-Identifier: MIT */
> +/*
> + * Copyright 2021 Advanced Micro Devices, Inc.
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a
> + * copy of this software and associated documentation files (the "Software"),
> + * to deal in the Software without restriction, including without limitation
> + * the rights to use, copy, modify, merge, publish, distribute, sublicense,
> + * and/or sell copies of the Software, and to permit persons to whom the
> + * Software is furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice shall be included in
> + * all copies or substantial portions of the Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
> + * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
> + * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
> + * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
> + * OTHER DEALINGS IN THE SOFTWARE.
> + *
> + * Authors: AMD
> + *
> + */
> +
> +#ifndef __DCN2X_H__
> +#define __DCN2X_H__
> +
> +void dcn20_populate_dml_writeback_from_context(struct dc *dc,
> +	struct resource_context *res_ctx, display_e2e_pipe_params_st *pipes);
> +
> +#endif /* __DCN2X_H__ */

[PATCH v2 2/4] drm/amd/display: Add FPU event trace

[Rodrigo Siqueira]

We don't have any mechanism for tracing FPU operations inside the
display core, making the debug work a little bit tricky. This commit
introduces a trace mechanism inside our DC_FP_START/END macros for
trying to alleviate this problem.

Signed-off-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
---
 .../gpu/drm/amd/display/amdgpu_dm/Makefile    |  3 +-
 .../amd/display/amdgpu_dm/amdgpu_dm_trace.h   | 21 ++++++
 .../gpu/drm/amd/display/amdgpu_dm/dc_fpu.c    | 64 +++++++++++++++++++
 .../gpu/drm/amd/display/amdgpu_dm/dc_fpu.h    | 33 ++++++++++
 drivers/gpu/drm/amd/display/dc/dc_trace.h     |  3 +
 drivers/gpu/drm/amd/display/dc/os_types.h     |  6 +-
 6 files changed, 126 insertions(+), 4 deletions(-)
 create mode 100644 drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c
 create mode 100644 drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.h

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/Makefile b/drivers/gpu/drm/amd/display/amdgpu_dm/Makefile
index 91fb72c96545..5f7fd4474379 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/Makefile
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/Makefile
@@ -25,7 +25,8 @@
 
 
 
-AMDGPUDM = amdgpu_dm.o amdgpu_dm_irq.o amdgpu_dm_mst_types.o amdgpu_dm_color.o
+AMDGPUDM = amdgpu_dm.o amdgpu_dm_irq.o amdgpu_dm_mst_types.o amdgpu_dm_color.o \
+	dc_fpu.o
 
 ifneq ($(CONFIG_DRM_AMD_DC),)
 AMDGPUDM += amdgpu_dm_services.o amdgpu_dm_helpers.o amdgpu_dm_pp_smu.o amdgpu_dm_psr.o
diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_trace.h b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_trace.h
index 46a33f64cf8e..230bb12c405e 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_trace.h
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_trace.h
@@ -637,6 +637,27 @@ TRACE_EVENT(amdgpu_refresh_rate_track,
 		  __entry->refresh_rate_ns)
 );
 
+TRACE_EVENT(dcn_fpu,
+	    TP_PROTO(bool begin, const char *function, const int line),
+	    TP_ARGS(begin, function, line),
+
+	    TP_STRUCT__entry(
+			     __field(bool, begin)
+			     __field(const char *, function)
+			     __field(int, line)
+	    ),
+	    TP_fast_assign(
+			   __entry->begin = begin;
+			   __entry->function = function;
+			   __entry->line = line;
+	    ),
+	    TP_printk("%s()+%d: %s",
+		      __entry->function,
+		      __entry->line,
+		      __entry->begin ? "begin" : "end"
+	    )
+);
+
 #endif /* _AMDGPU_DM_TRACE_H_ */
 
 #undef TRACE_INCLUDE_PATH
diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c b/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c
new file mode 100644
index 000000000000..d5d156a4517e
--- /dev/null
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c
@@ -0,0 +1,64 @@
+// SPDX-License-Identifier: MIT
+/*
+ * Copyright 2021 Advanced Micro Devices, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
+ * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+ * OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * Authors: AMD
+ *
+ */
+
+#include "dc_trace.h"
+
+#include <asm/fpu/api.h>
+
+/**
+ * dc_fpu_begin - Enables FPU protection
+ * @function_name: A string containing the function name for debug purposes
+ *   (usually __func__)
+ *
+ * @line: A line number where DC_FP_START was invoked for debug purpose
+ *   (usually __LINE__)
+ *
+ * This function is responsible for managing the use of kernel_fpu_begin() with
+ * the advantage of providing an event trace for debugging.
+ *
+ * Note: Do not call this function directly; always use DC_FP_START().
+ */
+void dc_fpu_begin(const char *function_name, const int line)
+{
+	TRACE_DCN_FPU(true, function_name, line);
+	kernel_fpu_begin();
+}
+
+/**
+ * dc_fpu_end - Disable FPU protection
+ * @function_name: A string containing the function name for debug purposes
+ * @line: A-line number where DC_FP_END was invoked for debug purpose
+ *
+ * This function is responsible for managing the use of kernel_fpu_end() with
+ * the advantage of providing an event trace for debugging.
+ *
+ * Note: Do not call this function directly; always use DC_FP_END().
+ */
+void dc_fpu_end(const char *function_name, const int line)
+{
+	TRACE_DCN_FPU(false, function_name, line);
+	kernel_fpu_end();
+}
diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.h b/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.h
new file mode 100644
index 000000000000..fb54983c5c60
--- /dev/null
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.h
@@ -0,0 +1,33 @@
+/* SPDX-License-Identifier: MIT */
+/*
+ * Copyright 2021 Advanced Micro Devices, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
+ * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+ * OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * Authors: AMD
+ *
+ */
+
+#ifndef __DC_FPU_H__
+#define __DC_FPU_H__
+
+void dc_fpu_begin(const char *function_name, const int line);
+void dc_fpu_end(const char *function_name, const int line);
+
+#endif /* __DC_FPU_H__ */
diff --git a/drivers/gpu/drm/amd/display/dc/dc_trace.h b/drivers/gpu/drm/amd/display/dc/dc_trace.h
index d2615357269b..d598ba697e45 100644
--- a/drivers/gpu/drm/amd/display/dc/dc_trace.h
+++ b/drivers/gpu/drm/amd/display/dc/dc_trace.h
@@ -37,3 +37,6 @@
 
 #define TRACE_DCN_CLOCK_STATE(dcn_clocks) \
 	trace_amdgpu_dm_dc_clocks_state(dcn_clocks)
+
+#define TRACE_DCN_FPU(begin, function, line) \
+	trace_dcn_fpu(begin, function, line)
diff --git a/drivers/gpu/drm/amd/display/dc/os_types.h b/drivers/gpu/drm/amd/display/dc/os_types.h
index 126c2f3a4dd3..2ba49aef370d 100644
--- a/drivers/gpu/drm/amd/display/dc/os_types.h
+++ b/drivers/gpu/drm/amd/display/dc/os_types.h
@@ -52,9 +52,9 @@
 
 #if defined(CONFIG_DRM_AMD_DC_DCN)
 #if defined(CONFIG_X86)
-#include <asm/fpu/api.h>
-#define DC_FP_START() kernel_fpu_begin()
-#define DC_FP_END() kernel_fpu_end()
+#include "amdgpu_dm/dc_fpu.h"
+#define DC_FP_START() dc_fpu_begin(__func__, __LINE__)
+#define DC_FP_END() dc_fpu_end(__func__, __LINE__)
 #elif defined(CONFIG_PPC64)
 #include <asm/switch_to.h>
 #include <asm/cputable.h>
-- 
2.25.1

Re: [PATCH v2 2/4] drm/amd/display: Add FPU event trace

[Christian König]

Am 13.07.21 um 16:06 schrieb Rodrigo Siqueira:
> We don't have any mechanism for tracing FPU operations inside the
> display core, making the debug work a little bit tricky. This commit
> introduces a trace mechanism inside our DC_FP_START/END macros for
> trying to alleviate this problem.
>
> Signed-off-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
> ---
>   .../gpu/drm/amd/display/amdgpu_dm/Makefile    |  3 +-
>   .../amd/display/amdgpu_dm/amdgpu_dm_trace.h   | 21 ++++++
>   .../gpu/drm/amd/display/amdgpu_dm/dc_fpu.c    | 64 +++++++++++++++++++
>   .../gpu/drm/amd/display/amdgpu_dm/dc_fpu.h    | 33 ++++++++++
>   drivers/gpu/drm/amd/display/dc/dc_trace.h     |  3 +
>   drivers/gpu/drm/amd/display/dc/os_types.h     |  6 +-
>   6 files changed, 126 insertions(+), 4 deletions(-)
>   create mode 100644 drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c
>   create mode 100644 drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.h
>
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/Makefile b/drivers/gpu/drm/amd/display/amdgpu_dm/Makefile
> index 91fb72c96545..5f7fd4474379 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/Makefile
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/Makefile
> @@ -25,7 +25,8 @@
>   
>   
>   
> -AMDGPUDM = amdgpu_dm.o amdgpu_dm_irq.o amdgpu_dm_mst_types.o amdgpu_dm_color.o
> +AMDGPUDM = amdgpu_dm.o amdgpu_dm_irq.o amdgpu_dm_mst_types.o amdgpu_dm_color.o \
> +	dc_fpu.o
>   
>   ifneq ($(CONFIG_DRM_AMD_DC),)
>   AMDGPUDM += amdgpu_dm_services.o amdgpu_dm_helpers.o amdgpu_dm_pp_smu.o amdgpu_dm_psr.o
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_trace.h b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_trace.h
> index 46a33f64cf8e..230bb12c405e 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_trace.h
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_trace.h
> @@ -637,6 +637,27 @@ TRACE_EVENT(amdgpu_refresh_rate_track,
>   		  __entry->refresh_rate_ns)
>   );
>   
> +TRACE_EVENT(dcn_fpu,
> +	    TP_PROTO(bool begin, const char *function, const int line),
> +	    TP_ARGS(begin, function, line),
> +
> +	    TP_STRUCT__entry(
> +			     __field(bool, begin)
> +			     __field(const char *, function)
> +			     __field(int, line)
> +	    ),
> +	    TP_fast_assign(
> +			   __entry->begin = begin;
> +			   __entry->function = function;
> +			   __entry->line = line;
> +	    ),
> +	    TP_printk("%s()+%d: %s",
> +		      __entry->function,
> +		      __entry->line,
> +		      __entry->begin ? "begin" : "end"
> +	    )
> +);
> +
>   #endif /* _AMDGPU_DM_TRACE_H_ */
>   
>   #undef TRACE_INCLUDE_PATH
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c b/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c
> new file mode 100644
> index 000000000000..d5d156a4517e
> --- /dev/null
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c
> @@ -0,0 +1,64 @@
> +// SPDX-License-Identifier: MIT
> +/*
> + * Copyright 2021 Advanced Micro Devices, Inc.
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a
> + * copy of this software and associated documentation files (the "Software"),
> + * to deal in the Software without restriction, including without limitation
> + * the rights to use, copy, modify, merge, publish, distribute, sublicense,
> + * and/or sell copies of the Software, and to permit persons to whom the
> + * Software is furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice shall be included in
> + * all copies or substantial portions of the Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
> + * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
> + * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
> + * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
> + * OTHER DEALINGS IN THE SOFTWARE.
> + *
> + * Authors: AMD
> + *
> + */
> +
> +#include "dc_trace.h"
> +
> +#include <asm/fpu/api.h>
> +
> +/**
> + * dc_fpu_begin - Enables FPU protection
> + * @function_name: A string containing the function name for debug purposes
> + *   (usually __func__)
> + *
> + * @line: A line number where DC_FP_START was invoked for debug purpose
> + *   (usually __LINE__)
> + *
> + * This function is responsible for managing the use of kernel_fpu_begin() with
> + * the advantage of providing an event trace for debugging.
> + *
> + * Note: Do not call this function directly; always use DC_FP_START().
> + */
> +void dc_fpu_begin(const char *function_name, const int line)
> +{
> +	TRACE_DCN_FPU(true, function_name, line);
> +	kernel_fpu_begin();

The build robot has pointed that out as well, the kernel_fpu_begin() and 
kernel_fpu_end() functions are x86 specific and don't exist on other 
architectures in this form.

> +}
> +
> +/**
> + * dc_fpu_end - Disable FPU protection
> + * @function_name: A string containing the function name for debug purposes
> + * @line: A-line number where DC_FP_END was invoked for debug purpose
> + *
> + * This function is responsible for managing the use of kernel_fpu_end() with
> + * the advantage of providing an event trace for debugging.
> + *
> + * Note: Do not call this function directly; always use DC_FP_END().
> + */
> +void dc_fpu_end(const char *function_name, const int line)
> +{
> +	TRACE_DCN_FPU(false, function_name, line);
> +	kernel_fpu_end();
> +}
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.h b/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.h
> new file mode 100644
> index 000000000000..fb54983c5c60
> --- /dev/null
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.h
> @@ -0,0 +1,33 @@
> +/* SPDX-License-Identifier: MIT */
> +/*
> + * Copyright 2021 Advanced Micro Devices, Inc.
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a
> + * copy of this software and associated documentation files (the "Software"),
> + * to deal in the Software without restriction, including without limitation
> + * the rights to use, copy, modify, merge, publish, distribute, sublicense,
> + * and/or sell copies of the Software, and to permit persons to whom the
> + * Software is furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice shall be included in
> + * all copies or substantial portions of the Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
> + * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
> + * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
> + * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
> + * OTHER DEALINGS IN THE SOFTWARE.
> + *
> + * Authors: AMD
> + *
> + */
> +
> +#ifndef __DC_FPU_H__
> +#define __DC_FPU_H__
> +
> +void dc_fpu_begin(const char *function_name, const int line);
> +void dc_fpu_end(const char *function_name, const int line);
> +
> +#endif /* __DC_FPU_H__ */
> diff --git a/drivers/gpu/drm/amd/display/dc/dc_trace.h b/drivers/gpu/drm/amd/display/dc/dc_trace.h
> index d2615357269b..d598ba697e45 100644
> --- a/drivers/gpu/drm/amd/display/dc/dc_trace.h
> +++ b/drivers/gpu/drm/amd/display/dc/dc_trace.h
> @@ -37,3 +37,6 @@
>   
>   #define TRACE_DCN_CLOCK_STATE(dcn_clocks) \
>   	trace_amdgpu_dm_dc_clocks_state(dcn_clocks)
> +
> +#define TRACE_DCN_FPU(begin, function, line) \
> +	trace_dcn_fpu(begin, function, line)
> diff --git a/drivers/gpu/drm/amd/display/dc/os_types.h b/drivers/gpu/drm/amd/display/dc/os_types.h
> index 126c2f3a4dd3..2ba49aef370d 100644
> --- a/drivers/gpu/drm/amd/display/dc/os_types.h
> +++ b/drivers/gpu/drm/amd/display/dc/os_types.h
> @@ -52,9 +52,9 @@
>   
>   #if defined(CONFIG_DRM_AMD_DC_DCN)
>   #if defined(CONFIG_X86)
> -#include <asm/fpu/api.h>
> -#define DC_FP_START() kernel_fpu_begin()
> -#define DC_FP_END() kernel_fpu_end()
> +#include "amdgpu_dm/dc_fpu.h"

You really want to include that independent of CONFIG_X86 I think.

Regards,
Christian.

> +#define DC_FP_START() dc_fpu_begin(__func__, __LINE__)
> +#define DC_FP_END() dc_fpu_end(__func__, __LINE__)
>   #elif defined(CONFIG_PPC64)
>   #include <asm/switch_to.h>
>   #include <asm/cputable.h>

[PATCH v2 3/4] drm/amd/display: Add control mechanism for FPU utilization

[Rodrigo Siqueira]

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 V1:
- Use a better variable names
- Use get_cpu_ptr and put_cpu_ptr to better balance preemption enable
and disable

Signed-off-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
---
 .../amd/display/amdgpu_dm/amdgpu_dm_trace.h   | 13 ++++---
 .../gpu/drm/amd/display/amdgpu_dm/dc_fpu.c    | 36 ++++++++++++++++---
 drivers/gpu/drm/amd/display/dc/dc_trace.h     |  4 +--
 3 files changed, 42 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_trace.h b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_trace.h
index 230bb12c405e..fdcaea22b456 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_trace.h
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_trace.h
@@ -638,23 +638,26 @@ TRACE_EVENT(amdgpu_refresh_rate_track,
 );
 
 TRACE_EVENT(dcn_fpu,
-	    TP_PROTO(bool begin, const char *function, const int line),
-	    TP_ARGS(begin, function, line),
+	    TP_PROTO(bool begin, const char *function, const int line, const int recursion_depth),
+	    TP_ARGS(begin, function, line, recursion_depth),
 
 	    TP_STRUCT__entry(
 			     __field(bool, begin)
 			     __field(const char *, function)
 			     __field(int, line)
+			     __field(int, recursion_depth)
 	    ),
 	    TP_fast_assign(
 			   __entry->begin = begin;
 			   __entry->function = function;
 			   __entry->line = line;
+			   __entry->recursion_depth = recursion_depth;
 	    ),
-	    TP_printk("%s()+%d: %s",
+	    TP_printk("%s: recursion_depth: %d: %s()+%d:",
+		      __entry->begin ? "begin" : "end",
+		      __entry->recursion_depth,
 		      __entry->function,
-		      __entry->line,
-		      __entry->begin ? "begin" : "end"
+		      __entry->line
 	    )
 );
 
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 d5d156a4517e..73179e9e859a 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c
@@ -28,6 +28,19 @@
 
 #include <asm/fpu/api.h>
 
+/**
+ * DOC: DC FPU manipulation overview
+ *
+ * DC core uses FPU operations in multiple parts of the code, which requires a
+ * more specialized way to manage these areas' entrance. To fulfill this
+ * requirement, we created some wrapper functions that encapsulate
+ * kernel_fpu_begin/end to better fit our need in the display component. In
+ * summary, in this file, you can find functions related to FPU operation
+ * management.
+ */
+
+static DEFINE_PER_CPU(int, fpu_recursion_depth);
+
 /**
  * dc_fpu_begin - Enables FPU protection
  * @function_name: A string containing the function name for debug purposes
@@ -43,8 +56,16 @@
  */
 void dc_fpu_begin(const char *function_name, const int line)
 {
-	TRACE_DCN_FPU(true, function_name, line);
-	kernel_fpu_begin();
+	int *pcpu;
+
+	pcpu = get_cpu_ptr(&fpu_recursion_depth);
+	*pcpu = this_cpu_inc_return(fpu_recursion_depth);
+
+	if (*pcpu == 1)
+		kernel_fpu_begin();
+
+	TRACE_DCN_FPU(true, function_name, line, *pcpu);
+	put_cpu_ptr(&fpu_recursion_depth);
 }
 
 /**
@@ -59,6 +80,13 @@ void dc_fpu_begin(const char *function_name, const int line)
  */
 void dc_fpu_end(const char *function_name, const int line)
 {
-	TRACE_DCN_FPU(false, function_name, line);
-	kernel_fpu_end();
+	int *pcpu;
+
+	pcpu = get_cpu_ptr(&fpu_recursion_depth);
+	*pcpu = this_cpu_dec_return(fpu_recursion_depth);
+	if (*pcpu <= 0)
+		kernel_fpu_end();
+
+	TRACE_DCN_FPU(false, function_name, line, *pcpu);
+	put_cpu_ptr(&fpu_recursion_depth);
 }
diff --git a/drivers/gpu/drm/amd/display/dc/dc_trace.h b/drivers/gpu/drm/amd/display/dc/dc_trace.h
index d598ba697e45..c711797e5c9e 100644
--- a/drivers/gpu/drm/amd/display/dc/dc_trace.h
+++ b/drivers/gpu/drm/amd/display/dc/dc_trace.h
@@ -38,5 +38,5 @@
 #define TRACE_DCN_CLOCK_STATE(dcn_clocks) \
 	trace_amdgpu_dm_dc_clocks_state(dcn_clocks)
 
-#define TRACE_DCN_FPU(begin, function, line) \
-	trace_dcn_fpu(begin, function, line)
+#define TRACE_DCN_FPU(begin, function, line, ref_count) \
+	trace_dcn_fpu(begin, function, line, ref_count)
-- 
2.25.1

Re: [PATCH v2 3/4] drm/amd/display: Add control mechanism for FPU utilization

[Christian König]

Am 13.07.21 um 16:06 schrieb Rodrigo Siqueira:
> 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 V1:
> - Use a better variable names
> - Use get_cpu_ptr and put_cpu_ptr to better balance preemption enable
> and disable
>
> Signed-off-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
> ---
>   .../amd/display/amdgpu_dm/amdgpu_dm_trace.h   | 13 ++++---
>   .../gpu/drm/amd/display/amdgpu_dm/dc_fpu.c    | 36 ++++++++++++++++---
>   drivers/gpu/drm/amd/display/dc/dc_trace.h     |  4 +--
>   3 files changed, 42 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_trace.h b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_trace.h
> index 230bb12c405e..fdcaea22b456 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_trace.h
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_trace.h
> @@ -638,23 +638,26 @@ TRACE_EVENT(amdgpu_refresh_rate_track,
>   );
>   
>   TRACE_EVENT(dcn_fpu,
> -	    TP_PROTO(bool begin, const char *function, const int line),
> -	    TP_ARGS(begin, function, line),
> +	    TP_PROTO(bool begin, const char *function, const int line, const int recursion_depth),
> +	    TP_ARGS(begin, function, line, recursion_depth),
>   
>   	    TP_STRUCT__entry(
>   			     __field(bool, begin)
>   			     __field(const char *, function)
>   			     __field(int, line)
> +			     __field(int, recursion_depth)
>   	    ),
>   	    TP_fast_assign(
>   			   __entry->begin = begin;
>   			   __entry->function = function;
>   			   __entry->line = line;
> +			   __entry->recursion_depth = recursion_depth;
>   	    ),
> -	    TP_printk("%s()+%d: %s",
> +	    TP_printk("%s: recursion_depth: %d: %s()+%d:",
> +		      __entry->begin ? "begin" : "end",
> +		      __entry->recursion_depth,
>   		      __entry->function,
> -		      __entry->line,
> -		      __entry->begin ? "begin" : "end"
> +		      __entry->line
>   	    )
>   );
>   
> 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 d5d156a4517e..73179e9e859a 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c
> @@ -28,6 +28,19 @@
>   
>   #include <asm/fpu/api.h>
>   
> +/**
> + * DOC: DC FPU manipulation overview
> + *
> + * DC core uses FPU operations in multiple parts of the code, which requires a
> + * more specialized way to manage these areas' entrance. To fulfill this
> + * requirement, we created some wrapper functions that encapsulate
> + * kernel_fpu_begin/end to better fit our need in the display component. In
> + * summary, in this file, you can find functions related to FPU operation
> + * management.
> + */
> +
> +static DEFINE_PER_CPU(int, fpu_recursion_depth);
> +
>   /**
>    * dc_fpu_begin - Enables FPU protection
>    * @function_name: A string containing the function name for debug purposes
> @@ -43,8 +56,16 @@
>    */
>   void dc_fpu_begin(const char *function_name, const int line)
>   {
> -	TRACE_DCN_FPU(true, function_name, line);
> -	kernel_fpu_begin();
> +	int *pcpu;
> +
> +	pcpu = get_cpu_ptr(&fpu_recursion_depth);
> +	*pcpu = this_cpu_inc_return(fpu_recursion_depth);

That doesn't make sense. Please don't use this_cpu_inc_return() in 
combination with get_cpu_ptr().

Christian.

> +
> +	if (*pcpu == 1)
> +		kernel_fpu_begin();
> +
> +	TRACE_DCN_FPU(true, function_name, line, *pcpu);
> +	put_cpu_ptr(&fpu_recursion_depth);
>   }
>   
>   /**
> @@ -59,6 +80,13 @@ void dc_fpu_begin(const char *function_name, const int line)
>    */
>   void dc_fpu_end(const char *function_name, const int line)
>   {
> -	TRACE_DCN_FPU(false, function_name, line);
> -	kernel_fpu_end();
> +	int *pcpu;
> +
> +	pcpu = get_cpu_ptr(&fpu_recursion_depth);
> +	*pcpu = this_cpu_dec_return(fpu_recursion_depth);
> +	if (*pcpu <= 0)
> +		kernel_fpu_end();
> +
> +	TRACE_DCN_FPU(false, function_name, line, *pcpu);
> +	put_cpu_ptr(&fpu_recursion_depth);
>   }
> diff --git a/drivers/gpu/drm/amd/display/dc/dc_trace.h b/drivers/gpu/drm/amd/display/dc/dc_trace.h
> index d598ba697e45..c711797e5c9e 100644
> --- a/drivers/gpu/drm/amd/display/dc/dc_trace.h
> +++ b/drivers/gpu/drm/amd/display/dc/dc_trace.h
> @@ -38,5 +38,5 @@
>   #define TRACE_DCN_CLOCK_STATE(dcn_clocks) \
>   	trace_amdgpu_dm_dc_clocks_state(dcn_clocks)
>   
> -#define TRACE_DCN_FPU(begin, function, line) \
> -	trace_dcn_fpu(begin, function, line)
> +#define TRACE_DCN_FPU(begin, function, line, ref_count) \
> +	trace_dcn_fpu(begin, function, line, ref_count)

[PATCH v2 4/4] drm/amd/display: Add DC_FP helper to check FPU state

[Rodrigo Siqueira]

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 since V1:
- Remove fp_enable variables
- Rename dc_is_fp_enabled to dc_assert_fp_enabled
- Replace wrong variable type

Signed-off-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
---
 .../gpu/drm/amd/display/amdgpu_dm/dc_fpu.c    | 22 +++++++++++++++++++
 .../gpu/drm/amd/display/amdgpu_dm/dc_fpu.h    |  1 +
 .../drm/amd/display/dc/dcn20/dcn20_resource.c |  2 ++
 .../drm/amd/display/dc/fpu_operations/dcn2x.c | 17 ++++++++++++++
 4 files changed, 42 insertions(+)

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 73179e9e859a..74153a2816f9 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c
@@ -41,6 +41,28 @@
 
 static DEFINE_PER_CPU(int, fpu_recursion_depth);
 
+/**
+ * dc_assert_fp_enabled - Check if FPU protection is enabled
+ *
+ * This function tells if the code is already under FPU protection or not. A
+ * function that works as an API for a set of FPU operations can use this
+ * function for checking if the caller invoked it after DC_FP_START(). For
+ * example, take a look at dcn2x.c file.
+ *
+ * Return:
+ * Return true if we already enabled FPU protection, otherwise return false.
+ */
+inline bool dc_assert_fp_enabled(void)
+{
+	int *pcpu, depth = 0;
+
+	pcpu = get_cpu_ptr(&fpu_recursion_depth);
+	depth = this_cpu_read(fpu_recursion_depth);
+	put_cpu_ptr(&fpu_recursion_depth);
+
+	return depth > 1;
+}
+
 /**
  * dc_fpu_begin - Enables FPU protection
  * @function_name: A string containing the function name for debug purposes
diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.h b/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.h
index fb54983c5c60..97941794b77c 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.h
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.h
@@ -27,6 +27,7 @@
 #ifndef __DC_FPU_H__
 #define __DC_FPU_H__
 
+bool dc_assert_fp_enabled(void);
 void dc_fpu_begin(const char *function_name, const int line);
 void dc_fpu_end(const char *function_name, const int line);
 
diff --git a/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c b/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c
index f99b09643a52..d0b34c7f99dc 100644
--- a/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c
+++ b/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c
@@ -2355,7 +2355,9 @@ int dcn20_populate_dml_pipes_from_context(
 	}
 
 	/* populate writeback information */
+	DC_FP_START();
 	dc->res_pool->funcs->populate_dml_writeback_from_context(dc, res_ctx, pipes);
+	DC_FP_END();
 
 	return pipe_cnt;
 }
diff --git a/drivers/gpu/drm/amd/display/dc/fpu_operations/dcn2x.c b/drivers/gpu/drm/amd/display/dc/fpu_operations/dcn2x.c
index c815d6c01d64..d8183da0c2b0 100644
--- a/drivers/gpu/drm/amd/display/dc/fpu_operations/dcn2x.c
+++ b/drivers/gpu/drm/amd/display/dc/fpu_operations/dcn2x.c
@@ -41,6 +41,22 @@
  *    that deals with FP register is contained within this call.
  * 3. All function that needs to be accessed outside this file requires a
  *    public interface that not uses any FPU reference.
+ * 4. Developers should not use DC_FP_START/END in this file, but they need to
+ *    ensure that the caller invokes it before access any function available in
+ *    this file. For this reason, public API in this file must invoke
+ *    ASSERT(dc_assert_fp_enabled());
+ *
+ * Let's expand a little bit more the idea in the code pattern number for. 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.
  */
 
 static noinline void _dcn20_populate_dml_writeback_from_context(struct dc *dc,
@@ -83,5 +99,6 @@ static noinline void _dcn20_populate_dml_writeback_from_context(struct dc *dc,
 void dcn20_populate_dml_writeback_from_context(struct dc *dc,
 	struct resource_context *res_ctx, display_e2e_pipe_params_st *pipes)
 {
+	ASSERT(dc_assert_fp_enabled());
 	_dcn20_populate_dml_writeback_from_context(dc, res_ctx, pipes);
 }
-- 
2.25.1

Re: [PATCH v2 4/4] drm/amd/display: Add DC_FP helper to check FPU state

[Christian König]

Am 13.07.21 um 16:06 schrieb Rodrigo Siqueira:
> 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 since V1:
> - Remove fp_enable variables
> - Rename dc_is_fp_enabled to dc_assert_fp_enabled
> - Replace wrong variable type
>
> Signed-off-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
> ---
>   .../gpu/drm/amd/display/amdgpu_dm/dc_fpu.c    | 22 +++++++++++++++++++
>   .../gpu/drm/amd/display/amdgpu_dm/dc_fpu.h    |  1 +
>   .../drm/amd/display/dc/dcn20/dcn20_resource.c |  2 ++
>   .../drm/amd/display/dc/fpu_operations/dcn2x.c | 17 ++++++++++++++
>   4 files changed, 42 insertions(+)
>
> 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 73179e9e859a..74153a2816f9 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c
> @@ -41,6 +41,28 @@
>   
>   static DEFINE_PER_CPU(int, fpu_recursion_depth);
>   
> +/**
> + * dc_assert_fp_enabled - Check if FPU protection is enabled
> + *
> + * This function tells if the code is already under FPU protection or not. A
> + * function that works as an API for a set of FPU operations can use this
> + * function for checking if the caller invoked it after DC_FP_START(). For
> + * example, take a look at dcn2x.c file.
> + *
> + * Return:
> + * Return true if we already enabled FPU protection, otherwise return false.
> + */
> +inline bool dc_assert_fp_enabled(void)

Assert indicates that you print a warning if the condition isn't meet, 
but you only return the condition.

Either rename the function or raise the warning directly.

> +{
> +	int *pcpu, depth = 0;
> +
> +	pcpu = get_cpu_ptr(&fpu_recursion_depth);
> +	depth = this_cpu_read(fpu_recursion_depth);
> +	put_cpu_ptr(&fpu_recursion_depth);

Again this doesn't make sense.

Either you use this_cpu_read() or your use get_cpu_ptr()/put_cpu_ptr(), 
but not both.

> +
> +	return depth > 1;
> +}
> +
>   /**
>    * dc_fpu_begin - Enables FPU protection
>    * @function_name: A string containing the function name for debug purposes
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.h b/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.h
> index fb54983c5c60..97941794b77c 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.h
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.h
> @@ -27,6 +27,7 @@
>   #ifndef __DC_FPU_H__
>   #define __DC_FPU_H__
>   
> +bool dc_assert_fp_enabled(void);
>   void dc_fpu_begin(const char *function_name, const int line);
>   void dc_fpu_end(const char *function_name, const int line);
>   
> diff --git a/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c b/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c
> index f99b09643a52..d0b34c7f99dc 100644
> --- a/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c
> +++ b/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c
> @@ -2355,7 +2355,9 @@ int dcn20_populate_dml_pipes_from_context(
>   	}
>   
>   	/* populate writeback information */
> +	DC_FP_START();
>   	dc->res_pool->funcs->populate_dml_writeback_from_context(dc, res_ctx, pipes);
> +	DC_FP_END();
>   
>   	return pipe_cnt;
>   }
> diff --git a/drivers/gpu/drm/amd/display/dc/fpu_operations/dcn2x.c b/drivers/gpu/drm/amd/display/dc/fpu_operations/dcn2x.c
> index c815d6c01d64..d8183da0c2b0 100644
> --- a/drivers/gpu/drm/amd/display/dc/fpu_operations/dcn2x.c
> +++ b/drivers/gpu/drm/amd/display/dc/fpu_operations/dcn2x.c
> @@ -41,6 +41,22 @@
>    *    that deals with FP register is contained within this call.
>    * 3. All function that needs to be accessed outside this file requires a
>    *    public interface that not uses any FPU reference.
> + * 4. Developers should not use DC_FP_START/END in this file, but they need to

This needs to be harder, e.g. "Developers must not use....".

Regards,
Christian.

> + *    ensure that the caller invokes it before access any function available in
> + *    this file. For this reason, public API in this file must invoke
> + *    ASSERT(dc_assert_fp_enabled());
> + *
> + * Let's expand a little bit more the idea in the code pattern number for. 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.
>    */
>   
>   static noinline void _dcn20_populate_dml_writeback_from_context(struct dc *dc,
> @@ -83,5 +99,6 @@ static noinline void _dcn20_populate_dml_writeback_from_context(struct dc *dc,
>   void dcn20_populate_dml_writeback_from_context(struct dc *dc,
>   	struct resource_context *res_ctx, display_e2e_pipe_params_st *pipes)
>   {
> +	ASSERT(dc_assert_fp_enabled());
>   	_dcn20_populate_dml_writeback_from_context(dc, res_ctx, pipes);
>   }