path: root/drivers/net/wireless/ath/ath5k/reset.c

/*
 * Copyright (c) 2004-2008 Reyk Floeter <reyk@openbsd.org>
 * Copyright (c) 2006-2008 Nick Kossifidis <mickflemm@gmail.com>
 * Copyright (c) 2007-2008 Luis Rodriguez <mcgrof@winlab.rutgers.edu>
 * Copyright (c) 2007-2008 Pavel Roskin <proski@gnu.org>
 * Copyright (c) 2007-2008 Jiri Slaby <jirislaby@gmail.com>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 *
 */

#define _ATH5K_RESET

/*****************************\
  Reset functions and helpers
\*****************************/

#include <linux/pci.h> 		/* To determine if a card is pci-e */
#include <linux/log2.h>
#include "ath5k.h"
#include "reg.h"
#include "base.h"
#include "debug.h"

/**
 * ath5k_hw_write_ofdm_timings - set OFDM timings on AR5212
 *
 * @ah: the &struct ath5k_hw
 * @channel: the currently set channel upon reset
 *
 * Write the delta slope coefficient (used on pilot tracking ?) for OFDM
 * operation on the AR5212 upon reset. This is a helper for ath5k_hw_reset().
 *
 * Since delta slope is floating point we split it on its exponent and
 * mantissa and provide these values on hw.
 *
 * For more infos i think this patent is related
 * http://www.freepatentsonline.com/7184495.html
 */
static inline int ath5k_hw_write_ofdm_timings(struct ath5k_hw *ah,
	struct ieee80211_channel *channel)
{
	/* Get exponent and mantissa and set it */
	u32 coef_scaled, coef_exp, coef_man,
		ds_coef_exp, ds_coef_man, clock;

	BUG_ON(!(ah->ah_version == AR5K_AR5212) ||
		!(channel->hw_value & CHANNEL_OFDM));

	/* Get coefficient
	 * ALGO: coef = (5 * clock * carrier_freq) / 2)
	 * we scale coef by shifting clock value by 24 for
	 * better precision since we use integers */
	/* TODO: Half/quarter rate */
	clock =  ath5k_hw_htoclock(1, channel->hw_value & CHANNEL_TURBO);

	coef_scaled = ((5 * (clock << 24)) / 2) / channel->center_freq;

	/* Get exponent
	 * ALGO: coef_exp = 14 - highest set bit position */
	coef_exp = ilog2(coef_scaled);

	/* Doesn't make sense if it's zero*/
	if (!coef_scaled || !coef_exp)
		return -EINVAL;

	/* Note: we've shifted coef_scaled by 24 */
	coef_exp = 14 - (coef_exp - 24);


	/* Get mantissa (significant digits)
	 * ALGO: coef_mant = floor(coef_scaled* 2^coef_exp+0.5) */
	coef_man = coef_scaled +
		(1 << (24 - coef_exp - 1));

	/* Calculate delta slope coefficient exponent
	 * and mantissa (remove scaling) and set them on hw */
	ds_coef_man = coef_man >> (24 - coef_exp);
	ds_coef_exp = coef_exp - 16;

	AR5K_REG_WRITE_BITS(