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1/* SPDX-License-Identifier: GPL-2.0 or MIT */
2
3/*
4 * Copyright (c) 2024 Intel
5 * Copyright (c) 2024 Red Hat
6 */
7
8#ifndef __DRM_PANIC_H__
9#define __DRM_PANIC_H__
10
11#include <linux/module.h>
12#include <linux/types.h>
13#include <linux/iosys-map.h>
14
15#include <drm/drm_device.h>
16#include <drm/drm_fourcc.h>
17
18/**
19 * struct drm_scanout_buffer - DRM scanout buffer
20 *
21 * This structure holds the information necessary for drm_panic to draw the
22 * panic screen, and display it.
23 */
24struct drm_scanout_buffer {
25 /**
26 * @format:
27 *
28 * drm format of the scanout buffer.
29 */
30 const struct drm_format_info *format;
31
32 /**
33 * @map:
34 *
35 * Virtual address of the scanout buffer, either in memory or iomem.
36 * The scanout buffer should be in linear format, and can be directly
37 * sent to the display hardware. Tearing is not an issue for the panic
38 * screen.
39 */
40 struct iosys_map map[DRM_FORMAT_MAX_PLANES];
41
42 /**
43 * @pages: Optional, if the scanout buffer is not mapped, set this field
44 * to the array of pages of the scanout buffer. The panic code will use
45 * kmap_local_page_try_from_panic() to map one page at a time to write
46 * all the pixels. This array shouldn't be allocated from the
47 * get_scanoutbuffer() callback.
48 * The scanout buffer should be in linear format.
49 */
50 struct page **pages;
51
52 /**
53 * @width: Width of the scanout buffer, in pixels.
54 */
55 unsigned int width;
56
57 /**
58 * @height: Height of the scanout buffer, in pixels.
59 */
60 unsigned int height;
61
62 /**
63 * @pitch: Length in bytes between the start of two consecutive lines.
64 */
65 unsigned int pitch[DRM_FORMAT_MAX_PLANES];
66
67 /**
68 * @set_pixel: Optional function, to set a pixel color on the
69 * framebuffer. It allows to handle special tiling format inside the
70 * driver. It takes precedence over the @map and @pages fields.
71 */
72 void (*set_pixel)(struct drm_scanout_buffer *sb, unsigned int x,
73 unsigned int y, u32 color);
74
75};
76
77#ifdef CONFIG_DRM_PANIC
78
79/**
80 * drm_panic_trylock - try to enter the panic printing critical section
81 * @dev: struct drm_device
82 * @flags: unsigned long irq flags you need to pass to the unlock() counterpart
83 *
84 * This function must be called by any panic printing code. The panic printing
85 * attempt must be aborted if the trylock fails.
86 *
87 * Panic printing code can make the following assumptions while holding the
88 * panic lock:
89 *
90 * - Anything protected by drm_panic_lock() and drm_panic_unlock() pairs is safe
91 * to access.
92 *
93 * - Furthermore the panic printing code only registers in drm_dev_unregister()
94 * and gets removed in drm_dev_unregister(). This allows the panic code to
95 * safely access any state which is invariant in between these two function
96 * calls, like the list of planes &drm_mode_config.plane_list or most of the
97 * struct drm_plane structure.
98 *
99 * Specifically thanks to the protection around plane updates in
100 * drm_atomic_helper_swap_state() the following additional guarantees hold:
101 *
102 * - It is safe to deference the drm_plane.state pointer.
103 *
104 * - Anything in struct drm_plane_state or the driver's subclass thereof which
105 * stays invariant after the atomic check code has finished is safe to access.
106 * Specifically this includes the reference counted pointers to framebuffer
107 * and buffer objects.
108 *
109 * - Anything set up by &drm_plane_helper_funcs.fb_prepare and cleaned up
110 * &drm_plane_helper_funcs.fb_cleanup is safe to access, as long as it stays
111 * invariant between these two calls. This also means that for drivers using
112 * dynamic buffer management the framebuffer is pinned, and therefer all
113 * relevant datastructures can be accessed without taking any further locks
114 * (which would be impossible in panic context anyway).
115 *
116 * - Importantly, software and hardware state set up by
117 * &drm_plane_helper_funcs.begin_fb_access and
118 * &drm_plane_helper_funcs.end_fb_access is not safe to access.
119 *
120 * Drivers must not make any assumptions about the actual state of the hardware,
121 * unless they explicitly protected these hardware access with drm_panic_lock()
122 * and drm_panic_unlock().
123 *
124 * Return:
125 * %0 when failing to acquire the raw spinlock, nonzero on success.
126 */
127#define drm_panic_trylock(dev, flags) \
128 raw_spin_trylock_irqsave(&(dev)->mode_config.panic_lock, flags)
129
130/**
131 * drm_panic_lock - protect panic printing relevant state
132 * @dev: struct drm_device
133 * @flags: unsigned long irq flags you need to pass to the unlock() counterpart
134 *
135 * This function must be called to protect software and hardware state that the
136 * panic printing code must be able to rely on. The protected sections must be
137 * as small as possible. It uses the irqsave/irqrestore variant, and can be
138 * called from irq handler. Examples include:
139 *
140 * - Access to peek/poke or other similar registers, if that is the way the
141 * driver prints the pixels into the scanout buffer at panic time.
142 *
143 * - Updates to pointers like &drm_plane.state, allowing the panic handler to
144 * safely deference these. This is done in drm_atomic_helper_swap_state().
145 *
146 * - An state that isn't invariant and that the driver must be able to access
147 * during panic printing.
148 */
149
150#define drm_panic_lock(dev, flags) \
151 raw_spin_lock_irqsave(&(dev)->mode_config.panic_lock, flags)
152
153/**
154 * drm_panic_unlock - end of the panic printing critical section
155 * @dev: struct drm_device
156 * @flags: irq flags that were returned when acquiring the lock
157 *
158 * Unlocks the raw spinlock acquired by either drm_panic_lock() or
159 * drm_panic_trylock().
160 */
161#define drm_panic_unlock(dev, flags) \
162 raw_spin_unlock_irqrestore(&(dev)->mode_config.panic_lock, flags)
163
164#else
165
166static inline bool drm_panic_trylock(struct drm_device *dev, unsigned long flags)
167{
168 return true;
169}
170
171static inline void drm_panic_lock(struct drm_device *dev, unsigned long flags) {}
172static inline void drm_panic_unlock(struct drm_device *dev, unsigned long flags) {}
173
174#endif
175
176#if defined(CONFIG_DRM_PANIC_SCREEN_QR_CODE)
177size_t drm_panic_qr_max_data_size(u8 version, size_t url_len);
178
179u8 drm_panic_qr_generate(const char *url, u8 *data, size_t data_len, size_t data_size,
180 u8 *tmp, size_t tmp_size);
181#endif
182
183#endif /* __DRM_PANIC_H__ */