drivers/gpu/drm/i915/i915_scatterlist.h

/*
 * SPDX-License-Identifier: MIT
 *
 * Copyright © 2016 Intel Corporation
 */

#ifndef I915_SCATTERLIST_H
#define I915_SCATTERLIST_H

#include <linux/pfn.h>
#include <linux/scatterlist.h>
#include <linux/swiotlb.h>

#include "i915_gem.h"

/*
 * Optimised SGL iterator for GEM objects
 */
static __always_inline struct sgt_iter {
	struct scatterlist *sgp;
	union {
		unsigned long pfn;
		dma_addr_t dma;
	};
	unsigned int curr;
	unsigned int max;
} __sgt_iter(struct scatterlist *sgl, bool dma) {
	struct sgt_iter s = { .sgp = sgl };

	if (s.sgp) {
		s.max = s.curr = s.sgp->offset;
		s.max += s.sgp->length;
		if (dma)
			s.dma = sg_dma_address(s.sgp);
		else
			s.pfn = page_to_pfn(sg_page(s.sgp));
	}

	return s;
}

static inline int __sg_page_count(const struct scatterlist *sg)
{
	return sg->length >> PAGE_SHIFT;
}

static inline struct scatterlist *____sg_next(struct scatterlist *sg)
{
	++sg;
	if (unlikely(sg_is_chain(sg)))
		sg = sg_chain_ptr(sg);
	return sg;
}

/**
 * __sg_next - return the next scatterlist entry in a list
 * @sg:		The current sg entry
 *
 * Description:
 *   If the entry is the last, return NULL; otherwise, step to the next
 *   element in the array (@sg@+1). If that's a chain pointer, follow it;
 *   otherwise just return the pointer to the current element.
 **/
static inline struct scatterlist *__sg_next(struct scatterlist *sg)
{
	return sg_is_last(sg) ? NULL : ____sg_next(sg);
}

/**
 * __for_each_sgt_dma - iterate over the DMA addresses of the given sg_table
 * @__dmap:	DMA address (output)
 * @__iter:	'struct sgt_iter' (iterator state, internal)
 * @__sgt:	sg_table to iterate over (input)
 * @__step:	step size
 */
#define __for_each_sgt_dma(__dmap, __iter, __sgt, __step)		\
	for ((__iter) = __sgt_iter((__sgt)->sgl, true);			\
	     ((__dmap) = (__iter).dma + (__iter).curr);			\
	     (((__iter).curr += (__step)) >= (__iter).max) ?		\
	     (__iter) = __sgt_iter(__sg_next((__iter).sgp), true), 0 : 0)

/**
 * for_each_sgt_page - iterate over the pages of the given sg_table
 * @__pp:	page pointer (output)
 * @__iter:	'struct sgt_iter' (iterator state, internal)
 * @__sgt:	sg_table to iterate over (input)
 */
#define for_each_sgt_page(__pp, __iter, __sgt)				\
	for ((__iter) = __sgt_iter((__sgt)->sgl, false);		\
	     ((__pp) = (__iter).pfn == 0 ? NULL :			\
	      pfn_to_page((__iter).pfn + ((__iter).curr >> PAGE_SHIFT))); \
	     (((__iter).curr += PAGE_SIZE) >= (__iter).max) ?		\
	     (__iter) = __sgt_iter(__sg_next((__iter).sgp), false), 0 : 0)

static inline unsigned int i915_sg_page_sizes(struct scatterlist *sg)
{
	unsigned int page_sizes;

	page_sizes = 0;
	while (sg) {
		GEM_BUG_ON(sg->offset);
		GEM_BUG_ON(!IS_ALIGNED(sg->length, PAGE_SIZE));
		page_sizes |= sg->length;
		sg = __sg_next(sg);
	}

	return page_sizes;
}

static inline unsigned int i915_sg_segment_size(void)
{
	unsigned int size = swiotlb_max_segment();

	if (size == 0)
		return SCATTERLIST_MAX_SEGMENT;

	size = rounddown(size, PAGE_SIZE);
	/* swiotlb_max_segment_size can return 1 byte when it means one page. */
	if (size < PAGE_SIZE)
		size = PAGE_SIZE;

	return size;
}

bool i915_sg_trim(struct sg_table *orig_st);

#endif