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