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
snd_sof_create_page_table(struct device * dev,struct snd_dma_buffer * dmab,unsigned char * page_table,size_t size)25 int 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 }
73 EXPORT_SYMBOL(snd_sof_create_page_table);
74
75 MODULE_LICENSE("Dual BSD/GPL");
76