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/* SPDX-License-Identifier: GPL-2.0-only */
/*
* imported from v3.18-rc1~52^2~248^2~1
*
*/
/*
* Copyright (C) 2005 Marc Kleine-Budde, Pengutronix
* Copyright (C) 2006 Andrey Volkov, Varma Electronics
* Copyright (C) 2008-2009 Wolfgang Grandegger <wg@grandegger.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the version 2 of the GNU General Public License
* as published by the Free Software Foundation
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, see <http://www.gnu.org/licenses/>.
*/
/*
* Bit-timing calculation derived from:
*
* Code based on LinCAN sources and H8S2638 project
* Copyright 2004-2006 Pavel Pisa - DCE FELK CVUT cz
* Copyright 2005 Stanislav Marek
* email: pisa@cmp.felk.cvut.cz
*
* Calculates proper bit-timing parameters for a specified bit-rate
* and sample-point, which can then be used to set the bit-timing
* registers of the CAN controller. You can find more information
* in the header file linux/can/netlink.h.
*/
static int can_update_spt(const struct can_bittiming_const *btc,
int sampl_pt, int tseg, int *tseg1, int *tseg2)
{
*tseg2 = tseg + 1 - (sampl_pt * (tseg + 1)) / 1000;
if (*tseg2 < btc->tseg2_min)
*tseg2 = btc->tseg2_min;
if (*tseg2 > btc->tseg2_max)
*tseg2 = btc->tseg2_max;
*tseg1 = tseg - *tseg2;
if (*tseg1 > btc->tseg1_max) {
*tseg1 = btc->tseg1_max;
*tseg2 = tseg - *tseg1;
}
return 1000 * (tseg + 1 - *tseg2) / (tseg + 1);
}
static int can_calc_bittiming(struct net_device *dev, struct can_bittiming *bt,
const struct can_bittiming_const *btc)
{
struct can_priv *priv = netdev_priv(dev);
long best_error = 1000000000, error = 0;
int best_tseg = 0, best_brp = 0, brp = 0;
int tsegall, tseg = 0, tseg1 = 0, tseg2 = 0;
int spt_error = 1000, spt = 0, sampl_pt;
long rate;
u64 v64;
/* Use CIA recommended sample points */
if (bt->sample_point) {
sampl_pt = bt->sample_point;
} else {
if (bt->bitrate > 800000)
sampl_pt = 750;
else if (bt->bitrate > 500000)
sampl_pt = 800;
else
sampl_pt = 875;
}
/* tseg even = round down, odd = round up */
for (tseg = (btc->tseg1_max + btc->tseg2_max) * 2 + 1;
tseg >= (btc->tseg1_min + btc->tseg2_min) * 2; tseg--) {
tsegall = 1 + tseg / 2;
/* Compute all possible tseg choices (tseg=tseg1+tseg2) */
brp = priv->clock.freq / (tsegall * bt->bitrate) + tseg % 2;
/* chose brp step which is possible in system */
brp = (brp / btc->brp_inc) * btc->brp_inc;
if ((brp < btc->brp_min) || (brp > btc->brp_max))
continue;
rate = priv->clock.freq / (brp * tsegall);
error = bt->bitrate - rate;
/* tseg brp biterror */
if (error < 0)
error = -error;
if (error > best_error)
continue;
best_error = error;
if (error == 0) {
spt = can_update_spt(btc, sampl_pt, tseg / 2,
&tseg1, &tseg2);
error = sampl_pt - spt;
if (error < 0)
error = -error;
if (error > spt_error)
continue;
spt_error = error;
}
best_tseg = tseg / 2;
best_brp = brp;
if (error == 0)
break;
}
if (best_error) {
/* Error in one-tenth of a percent */
error = (best_error * 1000) / bt->bitrate;
if (error > CAN_CALC_MAX_ERROR) {
netdev_err(dev,
"bitrate error %ld.%ld%% too high\n",
error / 10, error % 10);
return -EDOM;
} else {
netdev_warn(dev, "bitrate error %ld.%ld%%\n",
error / 10, error % 10);
}
}
/* real sample point */
bt->sample_point = can_update_spt(btc, sampl_pt, best_tseg,
&tseg1, &tseg2);
v64 = (u64)best_brp * 1000000000UL;
do_div(v64, priv->clock.freq);
bt->tq = (u32)v64;
bt->prop_seg = tseg1 / 2;
bt->phase_seg1 = tseg1 - bt->prop_seg;
bt->phase_seg2 = tseg2;
/* check for sjw user settings */
if (!bt->sjw || !btc->sjw_max)
bt->sjw = 1;
else {
/* bt->sjw is at least 1 -> sanitize upper bound to sjw_max */
if (bt->sjw > btc->sjw_max)
bt->sjw = btc->sjw_max;
/* bt->sjw must not be higher than tseg2 */
if (tseg2 < bt->sjw)
bt->sjw = tseg2;
}
bt->brp = best_brp;
/* real bit-rate */
bt->bitrate = priv->clock.freq / (bt->brp * (tseg1 + tseg2 + 1));
return 0;
}
/*
* Checks the validity of the specified bit-timing parameters prop_seg,
* phase_seg1, phase_seg2 and sjw and tries to determine the bitrate
* prescaler value brp. You can find more information in the header
* file linux/can/netlink.h.
*/
static int can_fixup_bittiming(struct net_device *dev, struct can_bittiming *bt,
const struct can_bittiming_const *btc)
{
struct can_priv *priv = netdev_priv(dev);
int tseg1, alltseg;
u64 brp64;
tseg1 = bt->prop_seg + bt->phase_seg1;
if (!bt->sjw)
bt->sjw = 1;
if (bt->sjw > btc->sjw_max ||
tseg1 < btc->tseg1_min || tseg1 > btc->tseg1_max ||
bt->phase_seg2 < btc->tseg2_min || bt->phase_seg2 > btc->tseg2_max)
return -ERANGE;
brp64 = (u64)priv->clock.freq * (u64)bt->tq;
if (btc->brp_inc > 1)
do_div(brp64, btc->brp_inc);
brp64 += 500000000UL - 1;
do_div(brp64, 1000000000UL); /* the practicable BRP */
if (btc->brp_inc > 1)
brp64 *= btc->brp_inc;
bt->brp = (u32)brp64;
if (bt->brp < btc->brp_min || bt->brp > btc->brp_max)
return -EINVAL;
alltseg = bt->prop_seg + bt->phase_seg1 + bt->phase_seg2 + 1;
bt->bitrate = priv->clock.freq / (bt->brp * alltseg);
bt->sample_point = ((tseg1 + 1) * 1000) / alltseg;
return 0;
}
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