path: root/drivers/media/test-drivers/vicodec/codec-fwht.c

// SPDX-License-Identifier: LGPL-2.1+
/*
 * Copyright 2016 Tom aan de Wiel
 * Copyright 2018 Cisco Systems, Inc. and/or its affiliates. All rights reserved.
 *
 * 8x8 Fast Walsh Hadamard Transform in sequency order based on the paper:
 *
 * A Recursive Algorithm for Sequency-Ordered Fast Walsh Transforms,
 * R.D. Brown, 1977
 */

#include <linux/string.h>
#include <linux/kernel.h>
#include "codec-fwht.h"

#define OVERFLOW_BIT BIT(14)

/*
 * Note: bit 0 of the header must always be 0. Otherwise it cannot
 * be guaranteed that the magic 8 byte sequence (see below) can
 * never occur in the rlc output.
 */
#define PFRAME_BIT BIT(15)
#define DUPS_MASK 0x1ffe

#define PBLOCK 0
#define IBLOCK 1

#define ALL_ZEROS 15

static const uint8_t zigzag[64] = {
	0,
	1,  8,
	2,  9, 16,
	3, 10, 17, 24,
	4, 11, 18, 25, 32,
	5, 12, 19, 26, 33, 40,
	6, 13, 20, 27, 34, 41, 48,
	7, 14, 21, 28, 35, 42, 49, 56,
	15, 22, 29, 36, 43, 50, 57,
	23, 30, 37, 44, 51, 58,
	31, 38, 45, 52, 59,
	39, 46, 53, 60,
	47, 54, 61,
	55, 62,
	63,
};

/*
 * noinline_for_stack to work around
 * https://bugs.llvm.org/show_bug.cgi?id=38809
 */
static int noinline_for_stack
rlc(const s16 *in, __be16 *output, int blocktype)
{
	s16 block[8 * 8];
	s16 *wp = block;
	int i = 0;
	int x, y;
	int ret = 0;

	/* read in block from framebuffer */
	int lastzero_run = 0;
	int to_encode;

	for (y = 0; y < 8; y++) {
		for (x = 0; x < 8; x++) {
			*wp = in[x + y * 8];
			wp++;
		}
	}

	/* keep track of amount of trailing zeros */
	for (i = 63; i >= 0 && !block[zigzag[i]]; i--)
		lastzero_run++;

	*output++ = (blocktype == PBLOCK ? htons(PFRAME_BIT) : 0);
	ret++;

	to_encode = 8 * 8 - (lastzero_run > 14 ? lastzero_run : 0);

	i = 0;
	while (i < to_encode) {
		int cnt = 0;
		int tmp;

		/* count leading zeros */
		while ((tmp = block[zigzag[i]]) == 0 && cnt < 14) {
			cnt++;
			i++;
			if (i == to_encode) {
				cnt--;
				break;
			}
		}
		/* 4 bits for run, 12 for coefficient (quantization by 4) */
		*output++ = htons((cnt | tmp << 4));
		i++;
		ret++;
	}
	if (lastzero_run > 14) {
		*output = htons(ALL_ZEROS | 0);
		ret++;
	}

	return ret;
}

/*
 * This function will worst-case increase rlc_in by 65*2 bytes:
 * one s16 value for the header and 8 * 8 coefficients of type s16.
 */
static noinline_for_stack u16
derlc(const __be16 **rlc_in, s16 *dwht_out, const __be16 *end_of_input)
{
	/* header */
	const __be16 *input = *rlc_in;
	u16 stat;
	int dec_count = 0;
	s16 block[8 * 8 + 16];
	s16 *wp = block;
	int i;

	if (input > end_of_input)
		return OVERFLOW_BIT;
	stat = ntohs(*input++);

	/*
	 * Now de-compress, it expands one byte to up to 15 bytes
	 * (or fills the remainder of the 64 bytes with zeroes if it
	 * is the last byte to expand).
	 *
	 * So block has to be 8 * 8 + 16 bytes, the '+ 16' is to
	 * allow for overflow if the incoming data was malformed.
	 */
	while (dec_count < 8 * 8) {
		s16 in;
		int length;
		int coeff;

		if (input > end_of_input)
			return OVERFLOW_BIT;
		in = ntohs(*input++);
		length = in & 0xf;
		coeff = in >> 4;

		/* fill remainder with zeros */
		if (length == 15) {
			for (i = 0; i < 64 - dec_count; i++)
				*wp++ = 0;
			break;
		}

		for (i = 0; i < length; i++)
			*wp++ = 0;
		*wp++ = coeff;
		dec_count += length + 1;
	}

	wp = block;

	for (i = 0; i < 64; i++) {
		int pos = zigzag[i];
		int y = pos / 8;
		int x = pos % 8;

		dwht_out[x + y * 8] = *wp++;
	}
	*rlc_in = input;
	return stat;
}

static const int quant_table[] = {
	2, 2, 2, 2, 2, 2,  2,  2,
	2, 2, 2, 2, 2, 2,  2,  2,
	2, 2, 2, 2, 2, 2,  2,  3,
	2, 2, 2, 2, 2, 2,  3,  6,
	2, 2, 2, 2, 2, 3,  6,  6,
	2, 2, 2, 2, 3, 6,  6,  6,
	2, 2, 2, 3, 6, 6,  6,  6,
	2, 2, 3, 6, 6, 6,  6,  8,
};

static const int quant_table_p[] = {
	3, 3, 3, 3, 3, 3,  3,  3,
	3, 3, 3, 3, 3, 3,  3,  3,
	3,