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 /** 56 * drm_panic_trylock - try to enter the panic printing critical section 57 * @dev: struct drm_device 58 * @flags: unsigned long irq flags you need to pass to the unlock() counterpart 59 * 60 * This function must be called by any panic printing code. The panic printing 61 * attempt must be aborted if the trylock fails. 62 * 63 * Panic printing code can make the following assumptions while holding the 64 * panic lock: 65 * 66 * - Anything protected by drm_panic_lock() and drm_panic_unlock() pairs is safe 67 * to access. 68 * 69 * - Furthermore the panic printing code only registers in drm_dev_unregister() 70 * and gets removed in drm_dev_unregister(). This allows the panic code to 71 * safely access any state which is invariant in between these two function 72 * calls, like the list of planes &drm_mode_config.plane_list or most of the 73 * struct drm_plane structure. 74 * 75 * Specifically thanks to the protection around plane updates in 76 * drm_atomic_helper_swap_state() the following additional guarantees hold: 77 * 78 * - It is safe to deference the drm_plane.state pointer. 79 * 80 * - Anything in struct drm_plane_state or the driver's subclass thereof which 81 * stays invariant after the atomic check code has finished is safe to access. 82 * Specifically this includes the reference counted pointers to framebuffer 83 * and buffer objects. 84 * 85 * - Anything set up by &drm_plane_helper_funcs.fb_prepare and cleaned up 86 * &drm_plane_helper_funcs.fb_cleanup is safe to access, as long as it stays 87 * invariant between these two calls. This also means that for drivers using 88 * dynamic buffer management the framebuffer is pinned, and therefer all 89 * relevant datastructures can be accessed without taking any further locks 90 * (which would be impossible in panic context anyway). 91 * 92 * - Importantly, software and hardware state set up by 93 * &drm_plane_helper_funcs.begin_fb_access and 94 * &drm_plane_helper_funcs.end_fb_access is not safe to access. 95 * 96 * Drivers must not make any assumptions about the actual state of the hardware, 97 * unless they explicitly protected these hardware access with drm_panic_lock() 98 * and drm_panic_unlock(). 99 * 100 * Return: 101 * %0 when failing to acquire the raw spinlock, nonzero on success. 102 */ 103 #define drm_panic_trylock(dev, flags) \ 104 raw_spin_trylock_irqsave(&(dev)->mode_config.panic_lock, flags) 105 106 /** 107 * drm_panic_lock - protect panic printing relevant state 108 * @dev: struct drm_device 109 * @flags: unsigned long irq flags you need to pass to the unlock() counterpart 110 * 111 * This function must be called to protect software and hardware state that the 112 * panic printing code must be able to rely on. The protected sections must be 113 * as small as possible. It uses the irqsave/irqrestore variant, and can be 114 * called from irq handler. Examples include: 115 * 116 * - Access to peek/poke or other similar registers, if that is the way the 117 * driver prints the pixels into the scanout buffer at panic time. 118 * 119 * - Updates to pointers like &drm_plane.state, allowing the panic handler to 120 * safely deference these. This is done in drm_atomic_helper_swap_state(). 121 * 122 * - An state that isn't invariant and that the driver must be able to access 123 * during panic printing. 124 */ 125 126 #define drm_panic_lock(dev, flags) \ 127 raw_spin_lock_irqsave(&(dev)->mode_config.panic_lock, flags) 128 129 /** 130 * drm_panic_unlock - end of the panic printing critical section 131 * @dev: struct drm_device 132 * @flags: irq flags that were returned when acquiring the lock 133 * 134 * Unlocks the raw spinlock acquired by either drm_panic_lock() or 135 * drm_panic_trylock(). 136 */ 137 #define drm_panic_unlock(dev, flags) \ 138 raw_spin_unlock_irqrestore(&(dev)->mode_config.panic_lock, flags) 139 140 #ifdef CONFIG_DRM_PANIC 141 142 void drm_panic_register(struct drm_device *dev); 143 void drm_panic_unregister(struct drm_device *dev); 144 145 #else 146 147 static inline void drm_panic_register(struct drm_device *dev) {} 148 static inline void drm_panic_unregister(struct drm_device *dev) {} 149 150 #endif 151 152 #endif /* __DRM_PANIC_H__ */ 153