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 * @pages: Optional, if the scanout buffer is not mapped, set this field 44 * to the array of pages of the scanout buffer. The panic code will use 45 * kmap_local_page_try_from_panic() to map one page at a time to write 46 * all the pixels. This array shouldn't be allocated from the 47 * get_scanoutbuffer() callback. 48 * The scanout buffer should be in linear format. 49 */ 50 struct page **pages; 51 52 /** 53 * @width: Width of the scanout buffer, in pixels. 54 */ 55 unsigned int width; 56 57 /** 58 * @height: Height of the scanout buffer, in pixels. 59 */ 60 unsigned int height; 61 62 /** 63 * @pitch: Length in bytes between the start of two consecutive lines. 64 */ 65 unsigned int pitch[DRM_FORMAT_MAX_PLANES]; 66 67 /** 68 * @set_pixel: Optional function, to set a pixel color on the 69 * framebuffer. It allows to handle special tiling format inside the 70 * driver. It takes precedence over the @map and @pages fields. 71 */ 72 void (*set_pixel)(struct drm_scanout_buffer *sb, unsigned int x, 73 unsigned int y, u32 color); 74 75 }; 76 77 #ifdef CONFIG_DRM_PANIC 78 79 /** 80 * drm_panic_trylock - try to enter the panic printing critical section 81 * @dev: struct drm_device 82 * @flags: unsigned long irq flags you need to pass to the unlock() counterpart 83 * 84 * This function must be called by any panic printing code. The panic printing 85 * attempt must be aborted if the trylock fails. 86 * 87 * Panic printing code can make the following assumptions while holding the 88 * panic lock: 89 * 90 * - Anything protected by drm_panic_lock() and drm_panic_unlock() pairs is safe 91 * to access. 92 * 93 * - Furthermore the panic printing code only registers in drm_dev_unregister() 94 * and gets removed in drm_dev_unregister(). This allows the panic code to 95 * safely access any state which is invariant in between these two function 96 * calls, like the list of planes &drm_mode_config.plane_list or most of the 97 * struct drm_plane structure. 98 * 99 * Specifically thanks to the protection around plane updates in 100 * drm_atomic_helper_swap_state() the following additional guarantees hold: 101 * 102 * - It is safe to deference the drm_plane.state pointer. 103 * 104 * - Anything in struct drm_plane_state or the driver's subclass thereof which 105 * stays invariant after the atomic check code has finished is safe to access. 106 * Specifically this includes the reference counted pointers to framebuffer 107 * and buffer objects. 108 * 109 * - Anything set up by &drm_plane_helper_funcs.fb_prepare and cleaned up 110 * &drm_plane_helper_funcs.fb_cleanup is safe to access, as long as it stays 111 * invariant between these two calls. This also means that for drivers using 112 * dynamic buffer management the framebuffer is pinned, and therefer all 113 * relevant datastructures can be accessed without taking any further locks 114 * (which would be impossible in panic context anyway). 115 * 116 * - Importantly, software and hardware state set up by 117 * &drm_plane_helper_funcs.begin_fb_access and 118 * &drm_plane_helper_funcs.end_fb_access is not safe to access. 119 * 120 * Drivers must not make any assumptions about the actual state of the hardware, 121 * unless they explicitly protected these hardware access with drm_panic_lock() 122 * and drm_panic_unlock(). 123 * 124 * Return: 125 * %0 when failing to acquire the raw spinlock, nonzero on success. 126 */ 127 #define drm_panic_trylock(dev, flags) \ 128 raw_spin_trylock_irqsave(&(dev)->mode_config.panic_lock, flags) 129 130 /** 131 * drm_panic_lock - protect panic printing relevant state 132 * @dev: struct drm_device 133 * @flags: unsigned long irq flags you need to pass to the unlock() counterpart 134 * 135 * This function must be called to protect software and hardware state that the 136 * panic printing code must be able to rely on. The protected sections must be 137 * as small as possible. It uses the irqsave/irqrestore variant, and can be 138 * called from irq handler. Examples include: 139 * 140 * - Access to peek/poke or other similar registers, if that is the way the 141 * driver prints the pixels into the scanout buffer at panic time. 142 * 143 * - Updates to pointers like &drm_plane.state, allowing the panic handler to 144 * safely deference these. This is done in drm_atomic_helper_swap_state(). 145 * 146 * - An state that isn't invariant and that the driver must be able to access 147 * during panic printing. 148 */ 149 150 #define drm_panic_lock(dev, flags) \ 151 raw_spin_lock_irqsave(&(dev)->mode_config.panic_lock, flags) 152 153 /** 154 * drm_panic_unlock - end of the panic printing critical section 155 * @dev: struct drm_device 156 * @flags: irq flags that were returned when acquiring the lock 157 * 158 * Unlocks the raw spinlock acquired by either drm_panic_lock() or 159 * drm_panic_trylock(). 160 */ 161 #define drm_panic_unlock(dev, flags) \ 162 raw_spin_unlock_irqrestore(&(dev)->mode_config.panic_lock, flags) 163 164 #else 165 166 static inline bool drm_panic_trylock(struct drm_device *dev, unsigned long flags) 167 { 168 return true; 169 } 170 171 static inline void drm_panic_lock(struct drm_device *dev, unsigned long flags) {} 172 static inline void drm_panic_unlock(struct drm_device *dev, unsigned long flags) {} 173 174 #endif 175 176 #if defined(CONFIG_DRM_PANIC_SCREEN_QR_CODE) 177 size_t drm_panic_qr_max_data_size(u8 version, size_t url_len); 178 179 u8 drm_panic_qr_generate(const char *url, u8 *data, size_t data_len, size_t data_size, 180 u8 *tmp, size_t tmp_size); 181 #endif 182 183 #endif /* __DRM_PANIC_H__ */ 184