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