1// SPDX-License-Identifier: MIT
2/*
3 * Copyright 2021 Advanced Micro Devices, Inc.
4 *
5 * Permission is hereby granted, free of charge, to any person obtaining a
6 * copy of this software and associated documentation files (the "Software"),
7 * to deal in the Software without restriction, including without limitation
8 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
9 * and/or sell copies of the Software, and to permit persons to whom the
10 * Software is furnished to do so, subject to the following conditions:
11 *
12 * The above copyright notice and this permission notice shall be included in
13 * all copies or substantial portions of the Software.
14 *
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
18 * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
19 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
20 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
21 * OTHER DEALINGS IN THE SOFTWARE.
22 *
23 * Authors: AMD
24 *
25 */
26
27#include "dc_trace.h"
28
29#include <linux/fpu.h>
30
31/**
32 * DOC: DC FPU manipulation overview
33 *
34 * DC core uses FPU operations in multiple parts of the code, which requires a
35 * more specialized way to manage these areas' entrance. To fulfill this
36 * requirement, we created some wrapper functions that encapsulate
37 * kernel_fpu_begin/end to better fit our need in the display component. In
38 * summary, in this file, you can find functions related to FPU operation
39 * management.
40 */
41
42static DEFINE_PER_CPU(int, fpu_recursion_depth);
43
44/**
45 * dc_assert_fp_enabled - Check if FPU protection is enabled
46 *
47 * This function tells if the code is already under FPU protection or not. A
48 * function that works as an API for a set of FPU operations can use this
49 * function for checking if the caller invoked it after DC_FP_START(). For
50 * example, take a look at dcn20_fpu.c file.
51 */
52inline void dc_assert_fp_enabled(void)
53{
54 int depth;
55
56 depth = __this_cpu_read(fpu_recursion_depth);
57
58 ASSERT(depth >= 1);
59}
60
61/**
62 * dc_fpu_begin - Enables FPU protection
63 * @function_name: A string containing the function name for debug purposes
64 * (usually __func__)
65 *
66 * @line: A line number where DC_FP_START was invoked for debug purpose
67 * (usually __LINE__)
68 *
69 * This function is responsible for managing the use of kernel_fpu_begin() with
70 * the advantage of providing an event trace for debugging.
71 *
72 * Note: Do not call this function directly; always use DC_FP_START().
73 */
74void dc_fpu_begin(const char *function_name, const int line)
75{
76 int depth;
77
78 WARN_ON_ONCE(!in_task());
79 preempt_disable();
80 depth = __this_cpu_inc_return(fpu_recursion_depth);
81 if (depth == 1) {
82 BUG_ON(!kernel_fpu_available());
83 kernel_fpu_begin();
84 }
85
86 TRACE_DCN_FPU(true, function_name, line, depth);
87}
88
89/**
90 * dc_fpu_end - Disable FPU protection
91 * @function_name: A string containing the function name for debug purposes
92 * @line: A-line number where DC_FP_END was invoked for debug purpose
93 *
94 * This function is responsible for managing the use of kernel_fpu_end() with
95 * the advantage of providing an event trace for debugging.
96 *
97 * Note: Do not call this function directly; always use DC_FP_END().
98 */
99void dc_fpu_end(const char *function_name, const int line)
100{
101 int depth;
102
103 depth = __this_cpu_dec_return(fpu_recursion_depth);
104 if (depth == 0) {
105 kernel_fpu_end();
106 } else {
107 WARN_ON_ONCE(depth < 0);
108 }
109
110 TRACE_DCN_FPU(false, function_name, line, depth);
111 preempt_enable();
112}
113

source code of linux/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c