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 * @private: private pointer that you can use in the callbacks 77 * set_pixel() 78 */ 79 void *private; 80 81 }; 82 83 #ifdef CONFIG_DRM_PANIC 84 85 /** 86 * drm_panic_trylock - try to enter the panic printing critical section 87 * @dev: struct drm_device 88 * @flags: unsigned long irq flags you need to pass to the unlock() counterpart 89 * 90 * This function must be called by any panic printing code. The panic printing 91 * attempt must be aborted if the trylock fails. 92 * 93 * Panic printing code can make the following assumptions while holding the 94 * panic lock: 95 * 96 * - Anything protected by drm_panic_lock() and drm_panic_unlock() pairs is safe 97 * to access. 98 * 99 * - Furthermore the panic printing code only registers in drm_dev_unregister() 100 * and gets removed in drm_dev_unregister(). This allows the panic code to 101 * safely access any state which is invariant in between these two function 102 * calls, like the list of planes &drm_mode_config.plane_list or most of the 103 * struct drm_plane structure. 104 * 105 * Specifically thanks to the protection around plane updates in 106 * drm_atomic_helper_swap_state() the following additional guarantees hold: 107 * 108 * - It is safe to deference the drm_plane.state pointer. 109 * 110 * - Anything in struct drm_plane_state or the driver's subclass thereof which 111 * stays invariant after the atomic check code has finished is safe to access. 112 * Specifically this includes the reference counted pointers to framebuffer 113 * and buffer objects. 114 * 115 * - Anything set up by &drm_plane_helper_funcs.fb_prepare and cleaned up 116 * &drm_plane_helper_funcs.fb_cleanup is safe to access, as long as it stays 117 * invariant between these two calls. This also means that for drivers using 118 * dynamic buffer management the framebuffer is pinned, and therefer all 119 * relevant datastructures can be accessed without taking any further locks 120 * (which would be impossible in panic context anyway). 121 * 122 * - Importantly, software and hardware state set up by 123 * &drm_plane_helper_funcs.begin_fb_access and 124 * &drm_plane_helper_funcs.end_fb_access is not safe to access. 125 * 126 * Drivers must not make any assumptions about the actual state of the hardware, 127 * unless they explicitly protected these hardware access with drm_panic_lock() 128 * and drm_panic_unlock(). 129 * 130 * Return: 131 * %0 when failing to acquire the raw spinlock, nonzero on success. 132 */ 133 #define drm_panic_trylock(dev, flags) \ 134 raw_spin_trylock_irqsave(&(dev)->mode_config.panic_lock, flags) 135 136 /** 137 * drm_panic_lock - protect panic printing relevant state 138 * @dev: struct drm_device 139 * @flags: unsigned long irq flags you need to pass to the unlock() counterpart 140 * 141 * This function must be called to protect software and hardware state that the 142 * panic printing code must be able to rely on. The protected sections must be 143 * as small as possible. It uses the irqsave/irqrestore variant, and can be 144 * called from irq handler. Examples include: 145 * 146 * - Access to peek/poke or other similar registers, if that is the way the 147 * driver prints the pixels into the scanout buffer at panic time. 148 * 149 * - Updates to pointers like &drm_plane.state, allowing the panic handler to 150 * safely deference these. This is done in drm_atomic_helper_swap_state(). 151 * 152 * - An state that isn't invariant and that the driver must be able to access 153 * during panic printing. 154 */ 155 156 #define drm_panic_lock(dev, flags) \ 157 raw_spin_lock_irqsave(&(dev)->mode_config.panic_lock, flags) 158 159 /** 160 * drm_panic_unlock - end of the panic printing critical section 161 * @dev: struct drm_device 162 * @flags: irq flags that were returned when acquiring the lock 163 * 164 * Unlocks the raw spinlock acquired by either drm_panic_lock() or 165 * drm_panic_trylock(). 166 */ 167 #define drm_panic_unlock(dev, flags) \ 168 raw_spin_unlock_irqrestore(&(dev)->mode_config.panic_lock, flags) 169 170 #else 171 172 static inline bool drm_panic_trylock(struct drm_device *dev, unsigned long flags) 173 { 174 return true; 175 } 176 177 static inline void drm_panic_lock(struct drm_device *dev, unsigned long flags) {} 178 static inline void drm_panic_unlock(struct drm_device *dev, unsigned long flags) {} 179 180 #endif 181 182 #if defined(CONFIG_DRM_PANIC_SCREEN_QR_CODE) 183 size_t drm_panic_qr_max_data_size(u8 version, size_t url_len); 184 185 u8 drm_panic_qr_generate(const char *url, u8 *data, size_t data_len, size_t data_size, 186 u8 *tmp, size_t tmp_size); 187 #endif 188 189 #endif /* __DRM_PANIC_H__ */ 190