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1/* SPDX-License-Identifier: GPL-2.0 or MIT */2 3/*4 * Copyright (c) 2024 Intel5 * Copyright (c) 2024 Red Hat6 */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 buffer20 *21 * This structure holds the information necessary for drm_panic to draw the22 * panic screen, and display it.23 */24struct 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 directly37 * sent to the display hardware. Tearing is not an issue for the panic38 * 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 the59 * framebuffer. It allows to handle special tiling format inside the60 * 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 section69 * @dev: struct drm_device70 * @flags: unsigned long irq flags you need to pass to the unlock() counterpart71 *72 * This function must be called by any panic printing code. The panic printing73 * attempt must be aborted if the trylock fails.74 *75 * Panic printing code can make the following assumptions while holding the76 * panic lock:77 *78 * - Anything protected by drm_panic_lock() and drm_panic_unlock() pairs is safe79 * 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 to83 * safely access any state which is invariant in between these two function84 * calls, like the list of planes &drm_mode_config.plane_list or most of the85 * struct drm_plane structure.86 *87 * Specifically thanks to the protection around plane updates in88 * 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 which93 * stays invariant after the atomic check code has finished is safe to access.94 * Specifically this includes the reference counted pointers to framebuffer95 * and buffer objects.96 *97 * - Anything set up by &drm_plane_helper_funcs.fb_prepare and cleaned up98 * &drm_plane_helper_funcs.fb_cleanup is safe to access, as long as it stays99 * invariant between these two calls. This also means that for drivers using100 * dynamic buffer management the framebuffer is pinned, and therefer all101 * relevant datastructures can be accessed without taking any further locks102 * (which would be impossible in panic context anyway).103 *104 * - Importantly, software and hardware state set up by105 * &drm_plane_helper_funcs.begin_fb_access and106 * &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 state120 * @dev: struct drm_device121 * @flags: unsigned long irq flags you need to pass to the unlock() counterpart122 *123 * This function must be called to protect software and hardware state that the124 * panic printing code must be able to rely on. The protected sections must be125 * as small as possible. It uses the irqsave/irqrestore variant, and can be126 * called from irq handler. Examples include:127 *128 * - Access to peek/poke or other similar registers, if that is the way the129 * driver prints the pixels into the scanout buffer at panic time.130 *131 * - Updates to pointers like &drm_plane.state, allowing the panic handler to132 * 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 access135 * 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 section143 * @dev: struct drm_device144 * @flags: irq flags that were returned when acquiring the lock145 *146 * Unlocks the raw spinlock acquired by either drm_panic_lock() or147 * 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