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261 lines
7.7 KiB
261 lines
7.7 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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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 <[email protected]> |
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*/ |
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#include <linux/can/dev.h> |
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#ifdef CONFIG_CAN_CALC_BITTIMING |
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#define CAN_CALC_MAX_ERROR 50 /* in one-tenth of a percent */ |
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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: [email protected] |
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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 |
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can_update_sample_point(const struct can_bittiming_const *btc, |
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unsigned int sample_point_nominal, unsigned int tseg, |
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unsigned int *tseg1_ptr, unsigned int *tseg2_ptr, |
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unsigned int *sample_point_error_ptr) |
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{ |
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unsigned int sample_point_error, best_sample_point_error = UINT_MAX; |
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unsigned int sample_point, best_sample_point = 0; |
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unsigned int tseg1, tseg2; |
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int i; |
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for (i = 0; i <= 1; i++) { |
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tseg2 = tseg + CAN_SYNC_SEG - |
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(sample_point_nominal * (tseg + CAN_SYNC_SEG)) / |
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1000 - i; |
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tseg2 = clamp(tseg2, btc->tseg2_min, 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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sample_point = 1000 * (tseg + CAN_SYNC_SEG - tseg2) / |
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(tseg + CAN_SYNC_SEG); |
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sample_point_error = abs(sample_point_nominal - sample_point); |
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if (sample_point <= sample_point_nominal && |
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sample_point_error < best_sample_point_error) { |
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best_sample_point = sample_point; |
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best_sample_point_error = sample_point_error; |
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*tseg1_ptr = tseg1; |
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*tseg2_ptr = tseg2; |
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} |
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} |
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if (sample_point_error_ptr) |
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*sample_point_error_ptr = best_sample_point_error; |
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return best_sample_point; |
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} |
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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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unsigned int bitrate; /* current bitrate */ |
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unsigned int bitrate_error; /* difference between current and nominal value */ |
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unsigned int best_bitrate_error = UINT_MAX; |
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unsigned int sample_point_error; /* difference between current and nominal value */ |
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unsigned int best_sample_point_error = UINT_MAX; |
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unsigned int sample_point_nominal; /* nominal sample point */ |
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unsigned int best_tseg = 0; /* current best value for tseg */ |
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unsigned int best_brp = 0; /* current best value for brp */ |
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unsigned int brp, tsegall, tseg, tseg1 = 0, tseg2 = 0; |
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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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sample_point_nominal = bt->sample_point; |
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} else { |
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if (bt->bitrate > 800000) |
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sample_point_nominal = 750; |
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else if (bt->bitrate > 500000) |
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sample_point_nominal = 800; |
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else |
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sample_point_nominal = 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 = CAN_SYNC_SEG + 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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/* choose 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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bitrate = priv->clock.freq / (brp * tsegall); |
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bitrate_error = abs(bt->bitrate - bitrate); |
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/* tseg brp biterror */ |
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if (bitrate_error > best_bitrate_error) |
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continue; |
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/* reset sample point error if we have a better bitrate */ |
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if (bitrate_error < best_bitrate_error) |
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best_sample_point_error = UINT_MAX; |
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can_update_sample_point(btc, sample_point_nominal, tseg / 2, |
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&tseg1, &tseg2, &sample_point_error); |
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if (sample_point_error > best_sample_point_error) |
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continue; |
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best_sample_point_error = sample_point_error; |
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best_bitrate_error = bitrate_error; |
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best_tseg = tseg / 2; |
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best_brp = brp; |
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if (bitrate_error == 0 && sample_point_error == 0) |
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break; |
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} |
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if (best_bitrate_error) { |
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/* Error in one-tenth of a percent */ |
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v64 = (u64)best_bitrate_error * 1000; |
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do_div(v64, bt->bitrate); |
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bitrate_error = (u32)v64; |
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if (bitrate_error > CAN_CALC_MAX_ERROR) { |
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netdev_err(dev, |
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"bitrate error %d.%d%% too high\n", |
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bitrate_error / 10, bitrate_error % 10); |
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return -EDOM; |
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} |
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netdev_warn(dev, "bitrate error %d.%d%%\n", |
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bitrate_error / 10, bitrate_error % 10); |
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} |
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/* real sample point */ |
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bt->sample_point = can_update_sample_point(btc, sample_point_nominal, |
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best_tseg, &tseg1, &tseg2, |
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NULL); |
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v64 = (u64)best_brp * 1000 * 1000 * 1000; |
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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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/* check for sjw user settings */ |
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if (!bt->sjw || !btc->sjw_max) { |
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bt->sjw = 1; |
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} else { |
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/* bt->sjw is at least 1 -> sanitize upper bound to sjw_max */ |
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if (bt->sjw > btc->sjw_max) |
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bt->sjw = btc->sjw_max; |
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/* bt->sjw must not be higher than tseg2 */ |
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if (tseg2 < bt->sjw) |
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bt->sjw = tseg2; |
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} |
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bt->brp = best_brp; |
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/* real bitrate */ |
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bt->bitrate = priv->clock.freq / |
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(bt->brp * (CAN_SYNC_SEG + tseg1 + tseg2)); |
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return 0; |
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} |
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#endif /* CONFIG_CAN_CALC_BITTIMING */ |
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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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/* Checks the validity of predefined bitrate settings */ |
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static int |
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can_validate_bitrate(struct net_device *dev, struct can_bittiming *bt, |
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const u32 *bitrate_const, |
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const unsigned int bitrate_const_cnt) |
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{ |
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struct can_priv *priv = netdev_priv(dev); |
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unsigned int i; |
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for (i = 0; i < bitrate_const_cnt; i++) { |
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if (bt->bitrate == bitrate_const[i]) |
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break; |
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} |
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if (i >= priv->bitrate_const_cnt) |
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return -EINVAL; |
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return 0; |
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} |
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int can_get_bittiming(struct net_device *dev, struct can_bittiming *bt, |
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const struct can_bittiming_const *btc, |
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const u32 *bitrate_const, |
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const unsigned int bitrate_const_cnt) |
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{ |
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int err; |
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/* Depending on the given can_bittiming parameter structure the CAN |
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* timing parameters are calculated based on the provided bitrate OR |
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* alternatively the CAN timing parameters (tq, prop_seg, etc.) are |
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* provided directly which are then checked and fixed up. |
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*/ |
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if (!bt->tq && bt->bitrate && btc) |
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err = can_calc_bittiming(dev, bt, btc); |
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else if (bt->tq && !bt->bitrate && btc) |
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err = can_fixup_bittiming(dev, bt, btc); |
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else if (!bt->tq && bt->bitrate && bitrate_const) |
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err = can_validate_bitrate(dev, bt, bitrate_const, |
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bitrate_const_cnt); |
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else |
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err = -EINVAL; |
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return err; |
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}
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