xref: /src/sys/arch/powerpc/ibm4xx/ibm4xx_460ex_pll.c

/*	$NetBSD: ibm4xx_460ex_pll.c,v 1.1 2026/09/28 20:41:00 rkujawa Exp $	*/

/*-
 * Copyright (c) 2026 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Radoslaw Kujawa.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * AMCC 460EX/GT PLL straps decode.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: ibm4xx_460ex_pll.c,v 1.1 2026/09/28 20:41:00 rkujawa Exp $");

#include <sys/param.h>
#include <sys/systm.h>

#include <powerpc/ibm4xx/cpu.h>
#include <powerpc/ibm4xx/dcr4xx.h>
#include <powerpc/ibm4xx/ibm4xx_460ex_pll.h>

/* LFSR coded divisors. */
static const uint8_t ibm4xx_460ex_fwdv_code[] = {
	0x00, 0x01, 0x0f, 0x04, 0x09, 0x0a, 0x0d, 0x0e, 0x03, 0x0c,
	0x05, 0x08, 0x07, 0x02, 0x0b, 0x06
};

static const uint8_t ibm4xx_460ex_fbdv_code[] = {
	0x00, 0xff, 0x7e, 0xfd, 0x7a, 0xf5, 0x6a, 0xd5, 0x2a, 0xd4,
	0x29, 0xd3, 0x26, 0xcc, 0x19, 0xb3, 0x67, 0xce, 0x1d, 0xbb,
	0x77, 0xee, 0x5d, 0xba, 0x74, 0xe9, 0x52, 0xa5, 0x4b, 0x96,
	0x2c, 0xd8, 0x31, 0xe3, 0x46, 0x8d, 0x1b, 0xb7, 0x6f, 0xde,
	0x3d, 0xfb, 0x76, 0xed, 0x5a, 0xb5, 0x6b, 0xd6, 0x2d, 0xdb,
	0x36, 0xec, 0x59, 0xb2, 0x64, 0xc9, 0x12, 0xa4, 0x48, 0x91,
	0x23, 0xc7, 0x0e, 0x9c, 0x38, 0xf0, 0x61, 0xc2, 0x05, 0x8b,
	0x17, 0xaf, 0x5f, 0xbe, 0x7c, 0xf9, 0x72, 0xe5, 0x4a, 0x95,
	0x2b, 0xd7, 0x2e, 0xdc, 0x39, 0xf3, 0x66, 0xcd, 0x1a, 0xb4,
	0x68, 0xd1, 0x22, 0xc4, 0x09, 0x93, 0x27, 0xcf, 0x1e, 0xbc,
	0x78, 0xf1, 0x62, 0xc5, 0x0a, 0x94, 0x28, 0xd0, 0x21, 0xc3,
	0x06, 0x8c, 0x18, 0xb0, 0x60, 0xc1, 0x02, 0x84, 0x08, 0x90,
	0x20, 0xc0, 0x01, 0x83, 0x07, 0x8f, 0x1f, 0xbf, 0x7f, 0xfe,
	0x7d, 0xfa, 0x75, 0xea, 0x55, 0xaa, 0x54, 0xa9, 0x53, 0xa6,
	0x4c, 0x99, 0x33, 0xe7, 0x4e, 0x9d, 0x3b, 0xf7, 0x6e, 0xdd,
	0x3a, 0xf4, 0x69, 0xd2, 0x25, 0xcb, 0x16, 0xac, 0x58, 0xb1,
	0x63, 0xc6, 0x0d, 0x9b, 0x37, 0xef, 0x5e, 0xbd, 0x7b, 0xf6,
	0x6d, 0xda, 0x35, 0xeb, 0x56, 0xad, 0x5b, 0xb6, 0x6c, 0xd9,
	0x32, 0xe4, 0x49, 0x92, 0x24, 0xc8, 0x11, 0xa3, 0x47, 0x8e,
	0x1c, 0xb8, 0x70, 0xe1, 0x42, 0x85, 0x0b, 0x97, 0x2f, 0xdf,
	0x3e, 0xfc, 0x79, 0xf2, 0x65, 0xca, 0x15, 0xab, 0x57, 0xae,
	0x5c, 0xb9, 0x73, 0xe6, 0x4d, 0x9a, 0x34, 0xe8, 0x51, 0xa2,
	0x44, 0x89, 0x13, 0xa7, 0x4f, 0x9e, 0x3c, 0xf8, 0x71, 0xe2,
	0x45, 0x8a, 0x14, 0xa8, 0x50, 0xa1, 0x43, 0x86, 0x0c, 0x98,
	0x30, 0xe0, 0x41, 0x82, 0x04, 0x88, 0x10, 0xa0, 0x40, 0x81,
	0x03, 0x87, 0x0f, 0x9f, 0x3f
};

static u_int
ibm4xx_460ex_pll_div(const uint8_t *tab, size_t n, uint32_t code)
{
	size_t i;

	for (i = 0; i < n; i++)
		if (tab[i] == code)
			return i + 1;
	return 0;
}

/*
 * The PLL clock in MHz. 0 if the straps don't have that configuration.
 */
u_int
ibm4xx_460ex_base_clock(uint32_t cpu_hz)
{
	uint32_t strap;
	u_int fwdva, fbdv;

	strap = mfsdr(DCR_SDR0_SDSTP0);
	if (__SHIFTOUT(strap, SDR0_SDSTP0_SEL) != 0)
		return 0;

	fwdva = ibm4xx_460ex_pll_div(ibm4xx_460ex_fwdv_code,
	    __arraycount(ibm4xx_460ex_fwdv_code),
	    __SHIFTOUT(strap, SDR0_SDSTP0_FWDVA));
	fbdv = ibm4xx_460ex_pll_div(ibm4xx_460ex_fbdv_code,
	    __arraycount(ibm4xx_460ex_fbdv_code),
	    __SHIFTOUT(strap, SDR0_SDSTP0_FBDV));
	if (fwdva == 0 || fbdv == 0)
		return 0;

	return ((cpu_hz / 100000) * fwdva / fbdv) / 10;
}