1// SPDX-License-Identifier: (GPL-2.0-only OR BSD-3-Clause)
2//
3// This file is provided under a dual BSD/GPLv2 license.  When using or
4// redistributing this file, you may do so under either license.
5//
6// Copyright(c) 2018-2022 Intel Corporation. All rights reserved.
7//
8// Author: Keyon Jie <yang.jie@linux.intel.com>
9//
10
11#include <asm/unaligned.h>
12#include <linux/io-64-nonatomic-lo-hi.h>
13#include <linux/device.h>
14#include <sound/memalloc.h>
15#include <linux/module.h>
16#include "sof-utils.h"
17
18/*
19 * Generic buffer page table creation.
20 * Take the each physical page address and drop the least significant unused
21 * bits from each (based on PAGE_SIZE). Then pack valid page address bits
22 * into compressed page table.
23 */
24
25int snd_sof_create_page_table(struct device *dev,
26			      struct snd_dma_buffer *dmab,
27			      unsigned char *page_table, size_t size)
28{
29	int i, pages;
30
31	pages = snd_sgbuf_aligned_pages(size);
32
33	dev_dbg(dev, "generating page table for %p size 0x%zx pages %d\n",
34		dmab->area, size, pages);
35
36	for (i = 0; i < pages; i++) {
37		/*
38		 * The number of valid address bits for each page is 20.
39		 * idx determines the byte position within page_table
40		 * where the current page's address is stored
41		 * in the compressed page_table.
42		 * This can be calculated by multiplying the page number by 2.5.
43		 */
44		u32 idx = (5 * i) >> 1;
45		u32 pfn = snd_sgbuf_get_addr(dmab, i * PAGE_SIZE) >> PAGE_SHIFT;
46		u8 *pg_table;
47
48		pg_table = (u8 *)(page_table + idx);
49
50		/*
51		 * pagetable compression:
52		 * byte 0     byte 1     byte 2     byte 3     byte 4     byte 5
53		 * ___________pfn 0__________ __________pfn 1___________  _pfn 2...
54		 * .... ....  .... ....  .... ....  .... ....  .... ....  ....
55		 * It is created by:
56		 * 1. set current location to 0, PFN index i to 0
57		 * 2. put pfn[i] at current location in Little Endian byte order
58		 * 3. calculate an intermediate value as
59		 *    x = (pfn[i+1] << 4) | (pfn[i] & 0xf)
60		 * 4. put x at offset (current location + 2) in LE byte order
61		 * 5. increment current location by 5 bytes, increment i by 2
62		 * 6. continue to (2)
63		 */
64		if (i & 1)
65			put_unaligned_le32((pg_table[0] & 0xf) | pfn << 4,
66					   pg_table);
67		else
68			put_unaligned_le32(pfn, pg_table);
69	}
70
71	return pages;
72}
73EXPORT_SYMBOL(snd_sof_create_page_table);
74
75MODULE_LICENSE("Dual BSD/GPL");
76