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 */ 24 struct 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 * @width: Width of the scanout buffer, in pixels. 44 */ 45 unsigned int width; 46 47 /** 48 * @height: Height of the scanout buffer, in pixels. 49 */ 50 unsigned int height; 51 52 /** 53 * @pitch: Length in bytes between the start of two consecutive lines. 54 */ 55 unsigned int pitch[DRM_FORMAT_MAX_PLANES]; 56 57 /** 58 * @set_pixel: Optional function, to set a pixel color on the 59 * framebuffer. It allows to handle special tiling format inside the 60 * driver. 61 */ 62 void (*set_pixel)(struct drm_scanout_buffer *sb, unsigned int x, 63 unsigned int y, u32 color); 64 65 }; 66 67 #ifdef CONFIG_DRM_PANIC 68 69 /** 70 * drm_panic_trylock - try to enter the panic printing critical section 71 * @dev: struct drm_device 72 * @flags: unsigned long irq flags you need to pass to the unlock() counterpart 73 * 74 * This function must be called by any panic printing code. The panic printing 75 * attempt must be aborted if the trylock fails. 76 * 77 * Panic printing code can make the following assumptions while holding the 78 * panic lock: 79 * 80 * - Anything protected by drm_panic_lock() and drm_panic_unlock() pairs is safe 81 * to access. 82 * 83 * - Furthermore the panic printing code only registers in drm_dev_unregister() 84 * and gets removed in drm_dev_unregister(). This allows the panic code to 85 * safely access any state which is invariant in between these two function 86 * calls, like the list of planes &drm_mode_config.plane_list or most of the 87 * struct drm_plane structure. 88 * 89 * Specifically thanks to the protection around plane updates in 90 * drm_atomic_helper_swap_state() the following additional guarantees hold: 91 * 92 * - It is safe to deference the drm_plane.state pointer. 93 * 94 * - Anything in struct drm_plane_state or the driver's subclass thereof which 95 * stays invariant after the atomic check code has finished is safe to access. 96 * Specifically this includes the reference counted pointers to framebuffer 97 * and buffer objects. 98 * 99 * - Anything set up by &drm_plane_helper_funcs.fb_prepare and cleaned up 100 * &drm_plane_helper_funcs.fb_cleanup is safe to access, as long as it stays 101 * invariant between these two calls. This also means that for drivers using 102 * dynamic buffer management the framebuffer is pinned, and therefer all 103 * relevant datastructures can be accessed without taking any further locks 104 * (which would be impossible in panic context anyway). 105 * 106 * - Importantly, software and hardware state set up by 107 * &drm_plane_helper_funcs.begin_fb_access and 108 * &drm_plane_helper_funcs.end_fb_access is not safe to access. 109 * 110 * Drivers must not make any assumptions about the actual state of the hardware, 111 * unless they explicitly protected these hardware access with drm_panic_lock() 112 * and drm_panic_unlock(). 113 * 114 * Return: 115 * %0 when failing to acquire the raw spinlock, nonzero on success. 116 */ 117 #define drm_panic_trylock(dev, flags) \ 118 raw_spin_trylock_irqsave(&(dev)->mode_config.panic_lock, flags) 119 120 /** 121 * drm_panic_lock - protect panic printing relevant state 122 * @dev: struct drm_device 123 * @flags: unsigned long irq flags you need to pass to the unlock() counterpart 124 * 125 * This function must be called to protect software and hardware state that the 126 * panic printing code must be able to rely on. The protected sections must be 127 * as small as possible. It uses the irqsave/irqrestore variant, and can be 128 * called from irq handler. Examples include: 129 * 130 * - Access to peek/poke or other similar registers, if that is the way the 131 * driver prints the pixels into the scanout buffer at panic time. 132 * 133 * - Updates to pointers like &drm_plane.state, allowing the panic handler to 134 * safely deference these. This is done in drm_atomic_helper_swap_state(). 135 * 136 * - An state that isn't invariant and that the driver must be able to access 137 * during panic printing. 138 */ 139 140 #define drm_panic_lock(dev, flags) \ 141 raw_spin_lock_irqsave(&(dev)->mode_config.panic_lock, flags) 142 143 /** 144 * drm_panic_unlock - end of the panic printing critical section 145 * @dev: struct drm_device 146 * @flags: irq flags that were returned when acquiring the lock 147 * 148 * Unlocks the raw spinlock acquired by either drm_panic_lock() or 149 * drm_panic_trylock(). 150 */ 151 #define drm_panic_unlock(dev, flags) \ 152 raw_spin_unlock_irqrestore(&(dev)->mode_config.panic_lock, flags) 153 154 #else 155 156 static inline bool drm_panic_trylock(struct drm_device *dev, unsigned long flags) 157 { 158 return true; 159 } 160 161 static inline void drm_panic_lock(struct drm_device *dev, unsigned long flags) {} 162 static inline void drm_panic_unlock(struct drm_device *dev, unsigned long flags) {} 163 164 #endif 165 166 #endif /* __DRM_PANIC_H__ */ 167