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