linux/drivers/gpu/drm/drm_fb_dma_helper.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * drm kms/fb dma helper functions
 *
 * Copyright (C) 2012 Analog Devices Inc.
 *   Author: Lars-Peter Clausen <[email protected]>
 *
 * Based on udl_fbdev.c
 *  Copyright (C) 2012 Red Hat
 */

#include <drm/drm_damage_helper.h>
#include <drm/drm_fb_dma_helper.h>
#include <drm/drm_fourcc.h>
#include <drm/drm_framebuffer.h>
#include <drm/drm_gem_dma_helper.h>
#include <drm/drm_gem_framebuffer_helper.h>
#include <drm/drm_panic.h>
#include <drm/drm_plane.h>
#include <linux/dma-mapping.h>
#include <linux/module.h>

/**
 * DOC: framebuffer dma helper functions
 *
 * Provides helper functions for creating a DMA-contiguous framebuffer.
 *
 * Depending on the platform, the buffers may be physically non-contiguous and
 * mapped through an IOMMU or a similar mechanism, or allocated from
 * physically-contiguous memory (using, for instance, CMA or a pool of memory
 * reserved at early boot). This is handled behind the scenes by the DMA mapping
 * API.
 *
 * drm_gem_fb_create() is used in the &drm_mode_config_funcs.fb_create
 * callback function to create a DMA-contiguous framebuffer.
 */

/**
 * drm_fb_dma_get_gem_obj() - Get DMA GEM object for framebuffer
 * @fb: The framebuffer
 * @plane: Which plane
 *
 * Return the DMA GEM object for given framebuffer.
 *
 * This function will usually be called from the CRTC callback functions.
 */
struct drm_gem_dma_object *drm_fb_dma_get_gem_obj(struct drm_framebuffer *fb,
						  unsigned int plane)
{ … }
EXPORT_SYMBOL_GPL(…);

/**
 * drm_fb_dma_get_gem_addr() - Get DMA (bus) address for framebuffer, for pixel
 * formats where values are grouped in blocks this will get you the beginning of
 * the block
 * @fb: The framebuffer
 * @state: Which state of drm plane
 * @plane: Which plane
 * Return the DMA GEM address for given framebuffer.
 *
 * This function will usually be called from the PLANE callback functions.
 */
dma_addr_t drm_fb_dma_get_gem_addr(struct drm_framebuffer *fb,
				   struct drm_plane_state *state,
				   unsigned int plane)
{ … }
EXPORT_SYMBOL_GPL(…);

/**
 * drm_fb_dma_sync_non_coherent - Sync GEM object to non-coherent backing
 *	memory
 * @drm: DRM device
 * @old_state: Old plane state
 * @state: New plane state
 *
 * This function can be used by drivers that use damage clips and have
 * DMA GEM objects backed by non-coherent memory. Calling this function
 * in a plane's .atomic_update ensures that all the data in the backing
 * memory have been written to RAM.
 */
void drm_fb_dma_sync_non_coherent(struct drm_device *drm,
				  struct drm_plane_state *old_state,
				  struct drm_plane_state *state)
{ … }
EXPORT_SYMBOL_GPL(…);

/**
 * drm_fb_dma_get_scanout_buffer - Provide a scanout buffer in case of panic
 * @plane: DRM primary plane
 * @sb: scanout buffer for the panic handler
 * Returns: 0 or negative error code
 *
 * Generic get_scanout_buffer() implementation, for drivers that uses the
 * drm_fb_dma_helper. It won't call vmap in the panic context, so the driver
 * should make sure the primary plane is vmapped, otherwise the panic screen
 * won't get displayed.
 */
int drm_fb_dma_get_scanout_buffer(struct drm_plane *plane,
				  struct drm_scanout_buffer *sb)
{ … }
EXPORT_SYMBOL(…);