1 // SPDX-License-Identifier: GPL-2.0-only
2 /* Copyright (C) 2005 Marc Kleine-Budde, Pengutronix
4  * Copyright (C) 2008-2009 Wolfgang Grandegger <[email protected]>
10 #define CAN_CALC_MAX_ERROR 50 /* in one-tenth of a percent */
12 /* Bit-timing calculation derived from:
15  * Copyright 2004-2006 Pavel Pisa - DCE FELK CVUT cz
19  * Calculates proper bit-timing parameters for a specified bit-rate
20  * and sample-point, which can then be used to set the bit-timing
36 		tseg2 = tseg + CAN_SYNC_SEG -  in can_update_sample_point()
38 			1000 - i;  in can_update_sample_point()
39 		tseg2 = clamp(tseg2, btc->tseg2_min, btc->tseg2_max);  in can_update_sample_point()
40 		tseg1 = tseg - tseg2;  in can_update_sample_point()
41 		if (tseg1 > btc->tseg1_max) {  in can_update_sample_point()
42 			tseg1 = btc->tseg1_max;  in can_update_sample_point()
43 			tseg2 = tseg - tseg1;  in can_update_sample_point()
46 		sample_point = 1000 * (tseg + CAN_SYNC_SEG - tseg2) /  in can_update_sample_point()
48 		sample_point_error = abs(sample_point_nominal - sample_point);  in can_update_sample_point()
82 	if (bt->sample_point) {  in can_calc_bittiming()
83 		sample_point_nominal = bt->sample_point;  in can_calc_bittiming()
85 		if (bt->bitrate > 800 * KILO /* BPS */)  in can_calc_bittiming()
87 		else if (bt->bitrate > 500 * KILO /* BPS */)  in can_calc_bittiming()
94 	for (tseg = (btc->tseg1_max + btc->tseg2_max) * 2 + 1;  in can_calc_bittiming()
95 	     tseg >= (btc->tseg1_min + btc->tseg2_min) * 2; tseg--) {  in can_calc_bittiming()
99 		brp = priv->clock.freq / (tsegall * bt->bitrate) + tseg % 2;  in can_calc_bittiming()
102 		brp = (brp / btc->brp_inc) * btc->brp_inc;  in can_calc_bittiming()
103 		if (brp < btc->brp_min || brp > btc->brp_max)  in can_calc_bittiming()
106 		bitrate = priv->clock.freq / (brp * tsegall);  in can_calc_bittiming()
107 		bitrate_error = abs(bt->bitrate - bitrate);  in can_calc_bittiming()
113 		/* reset sample point error if we have a better bitrate */  in can_calc_bittiming()
132 		/* Error in one-tenth of a percent */  in can_calc_bittiming()
134 		do_div(v64, bt->bitrate);  in can_calc_bittiming()
140 			return -EINVAL;  in can_calc_bittiming()
148 	bt->sample_point = can_update_sample_point(btc, sample_point_nominal,  in can_calc_bittiming()
153 	do_div(v64, priv->clock.freq);  in can_calc_bittiming()
154 	bt->tq = (u32)v64;  in can_calc_bittiming()
155 	bt->prop_seg = tseg1 / 2;  in can_calc_bittiming()
156 	bt->phase_seg1 = tseg1 - bt->prop_seg;  in can_calc_bittiming()
157 	bt->phase_seg2 = tseg2;  in can_calc_bittiming()
165 	bt->brp = best_brp;  in can_calc_bittiming()
168 	bt->bitrate = priv->clock.freq /  in can_calc_bittiming()
169 		(bt->brp * can_bit_time(bt));  in can_calc_bittiming()
184 	/* As specified in ISO 11898-1 section 11.3.3 "Transmitter  in can_calc_tdco()
188 	if (dbt->brp == 1 || dbt->brp == 2) {  in can_calc_tdco()
190 		u32 sample_point_in_tc = (CAN_SYNC_SEG + dbt->prop_seg +  in can_calc_tdco()
191 					  dbt->phase_seg1) * dbt->brp;  in can_calc_tdco()
193 		if (sample_point_in_tc < tdc_const->tdco_min)  in can_calc_tdco()
195 		tdc->tdco = min(sample_point_in_tc, tdc_const->tdco_max);  in can_calc_tdco()