193 lines
5.8 KiB
C
193 lines
5.8 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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#include "compat.h"
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/*
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* imported from v2.6.31-rc1~330^2~376
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*
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* 39549eef3587 can: CAN Network device driver and Netlink interface
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*
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* cherry-picked for easier integration:
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* 61463a30f652 can: make function can_get_bittiming static
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* aabdfd6adb80 can: replace the dev_dbg/info/err/... with the new netdev_xxx macros
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* 08da7da41ea4 can: provide a separate bittiming_const parameter to bittiming functions
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* b25a437206ed can: dev: remove unused variable from can_calc_bittiming() function
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*/
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/*
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* Copyright (C) 2005 Marc Kleine-Budde, Pengutronix
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* Copyright (C) 2006 Andrey Volkov, Varma Electronics
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* Copyright (C) 2008-2009 Wolfgang Grandegger <wg@grandegger.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the version 2 of the GNU General Public License
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* as published by the Free Software Foundation
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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/*
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* Bit-timing calculation derived from:
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*
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* Code based on LinCAN sources and H8S2638 project
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* Copyright 2004-2006 Pavel Pisa - DCE FELK CVUT cz
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* Copyright 2005 Stanislav Marek
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* email: pisa@cmp.felk.cvut.cz
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*
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* Calculates proper bit-timing parameters for a specified bit-rate
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* and sample-point, which can then be used to set the bit-timing
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* registers of the CAN controller. You can find more information
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* in the header file linux/can/netlink.h.
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*/
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static int can_update_spt(const struct can_bittiming_const *btc,
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int sampl_pt, int tseg, int *tseg1, int *tseg2)
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{
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*tseg2 = tseg + 1 - (sampl_pt * (tseg + 1)) / 1000;
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if (*tseg2 < btc->tseg2_min)
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*tseg2 = btc->tseg2_min;
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if (*tseg2 > btc->tseg2_max)
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*tseg2 = btc->tseg2_max;
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*tseg1 = tseg - *tseg2;
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if (*tseg1 > btc->tseg1_max) {
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*tseg1 = btc->tseg1_max;
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*tseg2 = tseg - *tseg1;
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}
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return 1000 * (tseg + 1 - *tseg2) / (tseg + 1);
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}
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static int can_calc_bittiming(struct net_device *dev, struct can_bittiming *bt,
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const struct can_bittiming_const *btc)
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{
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struct can_priv *priv = netdev_priv(dev);
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long best_error = 1000000000, error = 0;
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int best_tseg = 0, best_brp = 0, brp = 0;
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int tsegall, tseg = 0, tseg1 = 0, tseg2 = 0;
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int spt_error = 1000, spt = 0, sampl_pt;
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long rate;
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u64 v64;
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/* Use CIA recommended sample points */
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if (bt->sample_point) {
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sampl_pt = bt->sample_point;
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} else {
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if (bt->bitrate > 800000)
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sampl_pt = 750;
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else if (bt->bitrate > 500000)
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sampl_pt = 800;
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else
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sampl_pt = 875;
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}
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/* tseg even = round down, odd = round up */
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for (tseg = (btc->tseg1_max + btc->tseg2_max) * 2 + 1;
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tseg >= (btc->tseg1_min + btc->tseg2_min) * 2; tseg--) {
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tsegall = 1 + tseg / 2;
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/* Compute all possible tseg choices (tseg=tseg1+tseg2) */
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brp = priv->clock.freq / (tsegall * bt->bitrate) + tseg % 2;
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/* chose brp step which is possible in system */
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brp = (brp / btc->brp_inc) * btc->brp_inc;
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if ((brp < btc->brp_min) || (brp > btc->brp_max))
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continue;
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rate = priv->clock.freq / (brp * tsegall);
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error = bt->bitrate - rate;
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/* tseg brp biterror */
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if (error < 0)
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error = -error;
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if (error > best_error)
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continue;
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best_error = error;
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if (error == 0) {
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spt = can_update_spt(btc, sampl_pt, tseg / 2,
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&tseg1, &tseg2);
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error = sampl_pt - spt;
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if (error < 0)
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error = -error;
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if (error > spt_error)
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continue;
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spt_error = error;
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}
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best_tseg = tseg / 2;
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best_brp = brp;
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if (error == 0)
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break;
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}
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if (best_error) {
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/* Error in one-tenth of a percent */
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error = (best_error * 1000) / bt->bitrate;
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if (error > CAN_CALC_MAX_ERROR) {
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netdev_err(dev,
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"bitrate error %ld.%ld%% too high\n",
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error / 10, error % 10);
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return -EDOM;
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} else {
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netdev_warn(dev, "bitrate error %ld.%ld%%\n",
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error / 10, error % 10);
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}
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}
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/* real sample point */
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bt->sample_point = can_update_spt(btc, sampl_pt, best_tseg,
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&tseg1, &tseg2);
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v64 = (u64)best_brp * 1000000000UL;
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do_div(v64, priv->clock.freq);
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bt->tq = (u32)v64;
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bt->prop_seg = tseg1 / 2;
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bt->phase_seg1 = tseg1 - bt->prop_seg;
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bt->phase_seg2 = tseg2;
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bt->sjw = 1;
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bt->brp = best_brp;
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/* real bit-rate */
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bt->bitrate = priv->clock.freq / (bt->brp * (tseg1 + tseg2 + 1));
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return 0;
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}
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/*
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* Checks the validity of the specified bit-timing parameters prop_seg,
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* phase_seg1, phase_seg2 and sjw and tries to determine the bitrate
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* prescaler value brp. You can find more information in the header
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* file linux/can/netlink.h.
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*/
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static int can_fixup_bittiming(struct net_device *dev, struct can_bittiming *bt,
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const struct can_bittiming_const *btc)
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{
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struct can_priv *priv = netdev_priv(dev);
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int tseg1, alltseg;
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u64 brp64;
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tseg1 = bt->prop_seg + bt->phase_seg1;
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if (!bt->sjw)
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bt->sjw = 1;
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if (bt->sjw > btc->sjw_max ||
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tseg1 < btc->tseg1_min || tseg1 > btc->tseg1_max ||
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bt->phase_seg2 < btc->tseg2_min || bt->phase_seg2 > btc->tseg2_max)
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return -ERANGE;
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brp64 = (u64)priv->clock.freq * (u64)bt->tq;
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if (btc->brp_inc > 1)
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do_div(brp64, btc->brp_inc);
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brp64 += 500000000UL - 1;
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do_div(brp64, 1000000000UL); /* the practicable BRP */
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if (btc->brp_inc > 1)
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brp64 *= btc->brp_inc;
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bt->brp = (u32)brp64;
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if (bt->brp < btc->brp_min || bt->brp > btc->brp_max)
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return -EINVAL;
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alltseg = bt->prop_seg + bt->phase_seg1 + bt->phase_seg2 + 1;
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bt->bitrate = priv->clock.freq / (bt->brp * alltseg);
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bt->sample_point = ((tseg1 + 1) * 1000) / alltseg;
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return 0;
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}
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