76 lines
2.3 KiB
C
76 lines
2.3 KiB
C
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// SPDX-License-Identifier: (GPL-2.0-only OR BSD-3-Clause)
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//
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// This file is provided under a dual BSD/GPLv2 license. When using or
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// redistributing this file, you may do so under either license.
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//
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// Copyright(c) 2018-2022 Intel Corporation. All rights reserved.
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//
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// Author: Keyon Jie <yang.jie@linux.intel.com>
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//
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#include <asm/unaligned.h>
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#include <linux/io-64-nonatomic-lo-hi.h>
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#include <linux/device.h>
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#include <sound/memalloc.h>
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#include <linux/module.h>
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#include "sof-utils.h"
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/*
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* Generic buffer page table creation.
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* Take the each physical page address and drop the least significant unused
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* bits from each (based on PAGE_SIZE). Then pack valid page address bits
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* into compressed page table.
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*/
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int snd_sof_create_page_table(struct device *dev,
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struct snd_dma_buffer *dmab,
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unsigned char *page_table, size_t size)
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{
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int i, pages;
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pages = snd_sgbuf_aligned_pages(size);
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dev_dbg(dev, "generating page table for %p size 0x%zx pages %d\n",
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dmab->area, size, pages);
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for (i = 0; i < pages; i++) {
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/*
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* The number of valid address bits for each page is 20.
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* idx determines the byte position within page_table
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* where the current page's address is stored
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* in the compressed page_table.
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* This can be calculated by multiplying the page number by 2.5.
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*/
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u32 idx = (5 * i) >> 1;
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u32 pfn = snd_sgbuf_get_addr(dmab, i * PAGE_SIZE) >> PAGE_SHIFT;
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u8 *pg_table;
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pg_table = (u8 *)(page_table + idx);
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/*
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* pagetable compression:
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* byte 0 byte 1 byte 2 byte 3 byte 4 byte 5
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* ___________pfn 0__________ __________pfn 1___________ _pfn 2...
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* .... .... .... .... .... .... .... .... .... .... ....
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* It is created by:
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* 1. set current location to 0, PFN index i to 0
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* 2. put pfn[i] at current location in Little Endian byte order
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* 3. calculate an intermediate value as
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* x = (pfn[i+1] << 4) | (pfn[i] & 0xf)
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* 4. put x at offset (current location + 2) in LE byte order
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* 5. increment current location by 5 bytes, increment i by 2
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* 6. continue to (2)
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*/
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if (i & 1)
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put_unaligned_le32((pg_table[0] & 0xf) | pfn << 4,
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pg_table);
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else
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put_unaligned_le32(pfn, pg_table);
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}
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return pages;
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}
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EXPORT_SYMBOL(snd_sof_create_page_table);
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MODULE_LICENSE("Dual BSD/GPL");
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