[linux-2.6-block.git] / drivers / net / can / dev / bittiming.c

// SPDX-License-Identifier: GPL-2.0-only
/* Copyright (C) 2005 Marc Kleine-Budde, Pengutronix
 * Copyright (C) 2006 Andrey Volkov, Varma Electronics
 * Copyright (C) 2008-2009 Wolfgang Grandegger <wg@grandegger.com>
 */

#include <linux/units.h>
#include <linux/can/dev.h>

#ifdef CONFIG_CAN_CALC_BITTIMING
#define CAN_CALC_MAX_ERROR 50 /* in one-tenth of a percent */

/* 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_sample_point(const struct can_bittiming_const *btc,
			const unsigned int sample_point_nominal, const unsigned int tseg,
			unsigned int *tseg1_ptr, unsigned int *tseg2_ptr,
			unsigned int *sample_point_error_ptr)
{
	unsigned int sample_point_error, best_sample_point_error = UINT_MAX;
	unsigned int sample_point, best_sample_point = 0;
	unsigned int tseg1, tseg2;
	int i;

	for (i = 0; i <= 1; i++) {
		tseg2 = tseg + CAN_SYNC_SEG -
			(sample_point_nominal * (tseg + CAN_SYNC_SEG)) /
			1000 - i;
		tseg2 = clamp(tseg2, btc->tseg2_min, btc->tseg2_max);
		tseg1 = tseg - tseg2;
		if (tseg1 > btc->tseg1_max) {
			tseg1 = btc->tseg1_max;
			tseg2 = tseg - tseg1;
		}

		sample_point = 1000 * (tseg + CAN_SYNC_SEG - tseg2) /
			(tseg + CAN_SYNC_SEG);
		sample_point_error = abs(sample_point_nominal - sample_point);

		if (sample_point <= sample_point_nominal &&
		    sample_point_error < best_sample_point_error) {
			best_sample_point = sample_point;
			best_sample_point_error = sample_point_error;
			*tseg1_ptr = tseg1;
			*tseg2_ptr = tseg2;
		}
	}

	if (sample_point_error_ptr)
		*sample_point_error_ptr = best_sample_point_error;

	return best_sample_point;
}

int can_calc_bittiming(const struct net_device *dev, struct can_bittiming *bt,
		       const struct can_bittiming_const *btc)
{
	struct can_priv *priv = netdev_priv(dev);
	unsigned int bitrate;			/* current bitrate */
	unsigned int bitrate_error;		/* difference between current and nominal value */
	unsigned int best_bitrate_error = UINT_MAX;
	unsigned int sample_point_error;	/* difference between current and nominal value */
	unsigned int best_sample_point_error = UINT_MAX;
	unsigned int sample_point_nominal;	/* nominal sample point */
	unsigned int best_tseg = 0;		/* current best value for tseg */
	unsigned int best_brp = 0;		/* current best value for brp */
	unsigned int brp, tsegall, tseg, tseg1 = 0, tseg2 = 0;
	u64 v64;

	/* Use CiA recommended sample points */
	if (bt->sample_point) {
		sample_point_nominal = bt->sample_point;
	} else {
		if (bt->bitrate > 800 * KILO /* BPS */)
			sample_point_nominal = 750;
		else if (bt->bitrate > 500 * KILO /* BPS */)
			sample_point_nominal = 800;
		else
			sample_point_nominal = 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 = CAN_SYNC_SEG + tseg / 2;

		/* Compute all possible tseg choices (tseg=tseg1+tseg2) */
		brp = priv->clock.freq / (tsegall * bt->bitrate) + tseg % 2;

		/* choose 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;

		bitrate = priv->clock.freq / (brp * tsegall);
		bitrate_error = abs(bt->bitrate - bitrate);

		/* tseg brp biterror */
		if (bitrate_error > best_bitrate_error)
			continue;

		/* reset sample point error if we have a better bitrate */
		if (bitrate_error < best_bitrate_error)
			best_sample_point_error = UINT_MAX;

		can_update_sample_point(btc, sample_point_nominal, tseg / 2,
					&tseg1, &tseg2, &sample_point_error);
		if (sample_point_error >= best_sample_point_error)
			continue;

		best_sample_point_error = sample_point_error;
		best_bitrate_error = bitrate_error;
		best_tseg = tseg / 2;
		best_brp = brp;

		if (bitrate_error == 0 && sample_point_error == 0)
			break;
	}

	if (best_bitrate_error) {
		/* Error in one-tenth of a percent */
		v64 = (u64)best_bitrate_error * 1000;
		do_div(v64, bt->bitrate);
		bitrate_error = (u32)v64;
		if (bitrate_error > CAN_CALC_MAX_ERROR) {
			netdev_err(dev,
				   "bitrate error %d.%d%% too high\n",
				   bitrate_error / 10, bitrate_error % 10);
			return -EDOM;
		}
		netdev_warn(dev, "bitrate error %d.%d%%\n",
			    bitrate_error / 10, bitrate_error % 10);
	}

	/* real sample point */
	bt->sample_point = can_update_sample_point(btc, sample_point_nominal,
						   best_tseg, &tseg1, &tseg2,
						   NULL);

	v64 = (u64)best_brp * 1000 * 1000 * 1000;
	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 bitrate */
	bt->bitrate = priv->clock.freq /
		(bt->brp * (CAN_SYNC_SEG + tseg1 + tseg2));

	return 0;
}

void can_calc_tdco(struct can_tdc *tdc, const struct can_tdc_const *tdc_const,
		   const struct can_bittiming *dbt,
		   u32 *ctrlmode, u32 ctrlmode_supported)

{
	if (!tdc_const || !(ctrlmode_supported & CAN_CTRLMODE_TDC_AUTO))
		return;

	*ctrlmode &= ~CAN_CTRLMODE_TDC_MASK;

	/* As specified in ISO 11898-1 section 11.3.3 "Transmitter
	 * delay compensation" (TDC) is only applicable if data BRP is
	 * one or two.
	 */
	if (dbt->brp == 1 || dbt->brp == 2) {
		/* Sample point in clock periods */
		u32 sample_point_in_tc = (CAN_SYNC_SEG + dbt->prop_seg +
					  dbt->phase_seg1) * dbt->brp;

		if (sample_point_in_tc < tdc_const->tdco_min)
			return;
		tdc->tdco = min(sample_point_in_tc, tdc_const->tdco_max);
		*ctrlmode |= CAN_CTRLMODE_TDC_AUTO;
	}
}
#endif /* CONFIG_CAN_CALC_BITTIMING */

/* 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(const struct net_device *dev, struct can_bittiming *bt,
			       const struct can_bittiming_const *btc)
{
	const struct can_priv *priv = netdev_priv(dev);
	unsigned 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;
}

/* Checks the validity of predefined bitrate settings */
static int
can_validate_bitrate(const struct net_device *dev, const struct can_bittiming *bt,
		     const u32 *bitrate_const,
		     const unsigned int bitrate_const_cnt)
{
	unsigned int i;

	for (i = 0; i < bitrate_const_cnt; i++) {
		if (bt->bitrate == bitrate_const[i])
			return 0;
	}

	return -EINVAL;
}

int can_get_bittiming(const struct net_device *dev, struct can_bittiming *bt,
		      const struct can_bittiming_const *btc,
		      const u32 *bitrate_const,
		      const unsigned int bitrate_const_cnt)
{
	int err;

	/* Depending on the given can_bittiming parameter structure the CAN
	 * timing parameters are calculated based on the provided bitrate OR
	 * alternatively the CAN timing parameters (tq, prop_seg, etc.) are
	 * provided directly which are then checked and fixed up.
	 */
	if (!bt->tq && bt->bitrate && btc)
		err = can_calc_bittiming(dev, bt, btc);
	else if (bt->tq && !bt->bitrate && btc)
		err = can_fixup_bittiming(dev, bt, btc);
	else if (!bt->tq && bt->bitrate && bitrate_const)
		err = can_validate_bitrate(dev, bt, bitrate_const,
					   bitrate_const_cnt);
	else
		err = -EINVAL;

	return err;
}
Commit	Line	Data
5a9d5ecd MKB	1	// SPDX-License-Identifier: GPL-2.0-only
	2	/* Copyright (C) 2005 Marc Kleine-Budde, Pengutronix
	3	* Copyright (C) 2006 Andrey Volkov, Varma Electronics
	4	* Copyright (C) 2008-2009 Wolfgang Grandegger <wg@grandegger.com>
	5	*/
	6
330c6d3b	7	#include <linux/units.h>
5a9d5ecd MKB	8	#include <linux/can/dev.h>
	9
	10	#ifdef CONFIG_CAN_CALC_BITTIMING
	11	#define CAN_CALC_MAX_ERROR 50 /* in one-tenth of a percent */
	12
	13	/* Bit-timing calculation derived from:
	14	*
	15	* Code based on LinCAN sources and H8S2638 project
	16	* Copyright 2004-2006 Pavel Pisa - DCE FELK CVUT cz
	17	* Copyright 2005 Stanislav Marek
	18	* email: pisa@cmp.felk.cvut.cz
	19	*
	20	* Calculates proper bit-timing parameters for a specified bit-rate
	21	* and sample-point, which can then be used to set the bit-timing
	22	* registers of the CAN controller. You can find more information
	23	* in the header file linux/can/netlink.h.
	24	*/
	25	static int
	26	can_update_sample_point(const struct can_bittiming_const *btc,
5597f082	27	const unsigned int sample_point_nominal, const unsigned int tseg,
5a9d5ecd MKB	28	unsigned int tseg1_ptr, unsigned int tseg2_ptr,
	29	unsigned int *sample_point_error_ptr)
	30	{
	31	unsigned int sample_point_error, best_sample_point_error = UINT_MAX;
	32	unsigned int sample_point, best_sample_point = 0;
	33	unsigned int tseg1, tseg2;
	34	int i;
	35
	36	for (i = 0; i <= 1; i++) {
	37	tseg2 = tseg + CAN_SYNC_SEG -
	38	(sample_point_nominal * (tseg + CAN_SYNC_SEG)) /
	39	1000 - i;
	40	tseg2 = clamp(tseg2, btc->tseg2_min, btc->tseg2_max);
	41	tseg1 = tseg - tseg2;
	42	if (tseg1 > btc->tseg1_max) {
	43	tseg1 = btc->tseg1_max;
	44	tseg2 = tseg - tseg1;
	45	}
	46
	47	sample_point = 1000 * (tseg + CAN_SYNC_SEG - tseg2) /
	48	(tseg + CAN_SYNC_SEG);
	49	sample_point_error = abs(sample_point_nominal - sample_point);
	50
	51	if (sample_point <= sample_point_nominal &&
	52	sample_point_error < best_sample_point_error) {
	53	best_sample_point = sample_point;
	54	best_sample_point_error = sample_point_error;
	55	*tseg1_ptr = tseg1;
	56	*tseg2_ptr = tseg2;
	57	}
	58	}
	59
	60	if (sample_point_error_ptr)
	61	*sample_point_error_ptr = best_sample_point_error;
	62
	63	return best_sample_point;
	64	}
	65
5597f082	66	int can_calc_bittiming(const struct net_device dev, struct can_bittiming bt,
5a9d5ecd MKB	67	const struct can_bittiming_const *btc)
	68	{
	69	struct can_priv *priv = netdev_priv(dev);
	70	unsigned int bitrate; /* current bitrate */
	71	unsigned int bitrate_error; /* difference between current and nominal value */
	72	unsigned int best_bitrate_error = UINT_MAX;
	73	unsigned int sample_point_error; /* difference between current and nominal value */
	74	unsigned int best_sample_point_error = UINT_MAX;
	75	unsigned int sample_point_nominal; /* nominal sample point */
	76	unsigned int best_tseg = 0; /* current best value for tseg */
	77	unsigned int best_brp = 0; /* current best value for brp */
	78	unsigned int brp, tsegall, tseg, tseg1 = 0, tseg2 = 0;
	79	u64 v64;
	80
	81	/* Use CiA recommended sample points */
	82	if (bt->sample_point) {
	83	sample_point_nominal = bt->sample_point;
	84	} else {
330c6d3b	85	if (bt->bitrate > 800 * KILO /* BPS */)
5a9d5ecd	86	sample_point_nominal = 750;
330c6d3b	87	else if (bt->bitrate > 500 * KILO /* BPS */)
5a9d5ecd MKB	88	sample_point_nominal = 800;
	89	else
	90	sample_point_nominal = 875;
	91	}
	92
	93	/* tseg even = round down, odd = round up */
	94	for (tseg = (btc->tseg1_max + btc->tseg2_max) * 2 + 1;
	95	tseg >= (btc->tseg1_min + btc->tseg2_min) * 2; tseg--) {
	96	tsegall = CAN_SYNC_SEG + tseg / 2;
	97
	98	/* Compute all possible tseg choices (tseg=tseg1+tseg2) */
	99	brp = priv->clock.freq / (tsegall * bt->bitrate) + tseg % 2;
	100
	101	/* choose brp step which is possible in system */
	102	brp = (brp / btc->brp_inc) * btc->brp_inc;
	103	if (brp < btc->brp_min \|\| brp > btc->brp_max)
	104	continue;
	105
	106	bitrate = priv->clock.freq / (brp * tsegall);
	107	bitrate_error = abs(bt->bitrate - bitrate);
	108
	109	/* tseg brp biterror */
	110	if (bitrate_error > best_bitrate_error)
	111	continue;
	112
	113	/* reset sample point error if we have a better bitrate */
	114	if (bitrate_error < best_bitrate_error)
	115	best_sample_point_error = UINT_MAX;
	116
	117	can_update_sample_point(btc, sample_point_nominal, tseg / 2,
	118	&tseg1, &tseg2, &sample_point_error);
85d4eb2a	119	if (sample_point_error >= best_sample_point_error)
5a9d5ecd MKB	120	continue;
	121
	122	best_sample_point_error = sample_point_error;
	123	best_bitrate_error = bitrate_error;
	124	best_tseg = tseg / 2;
	125	best_brp = brp;
	126
	127	if (bitrate_error == 0 && sample_point_error == 0)
	128	break;
	129	}
	130
	131	if (best_bitrate_error) {
	132	/* Error in one-tenth of a percent */
	133	v64 = (u64)best_bitrate_error * 1000;
	134	do_div(v64, bt->bitrate);
	135	bitrate_error = (u32)v64;
	136	if (bitrate_error > CAN_CALC_MAX_ERROR) {
	137	netdev_err(dev,
	138	"bitrate error %d.%d%% too high\n",
	139	bitrate_error / 10, bitrate_error % 10);
	140	return -EDOM;
	141	}
	142	netdev_warn(dev, "bitrate error %d.%d%%\n",
	143	bitrate_error / 10, bitrate_error % 10);
	144	}
	145
	146	/* real sample point */
	147	bt->sample_point = can_update_sample_point(btc, sample_point_nominal,
	148	best_tseg, &tseg1, &tseg2,
	149	NULL);
	150
	151	v64 = (u64)best_brp * 1000 * 1000 * 1000;
	152	do_div(v64, priv->clock.freq);
	153	bt->tq = (u32)v64;
	154	bt->prop_seg = tseg1 / 2;
	155	bt->phase_seg1 = tseg1 - bt->prop_seg;
	156	bt->phase_seg2 = tseg2;
	157
	158	/* check for sjw user settings */
	159	if (!bt->sjw \|\| !btc->sjw_max) {
	160	bt->sjw = 1;
	161	} else {
	162	/* bt->sjw is at least 1 -> sanitize upper bound to sjw_max */
	163	if (bt->sjw > btc->sjw_max)
	164	bt->sjw = btc->sjw_max;
	165	/* bt->sjw must not be higher than tseg2 */
	166	if (tseg2 < bt->sjw)
	167	bt->sjw = tseg2;
	168	}
	169
	170	bt->brp = best_brp;
	171
	172	/* real bitrate */
	173	bt->bitrate = priv->clock.freq /
	174	(bt->brp * (CAN_SYNC_SEG + tseg1 + tseg2));
	175
	176	return 0;
	177	}
c25cc799	178
da45a1e4 VM	179	void can_calc_tdco(struct can_tdc tdc, const struct can_tdc_const tdc_const,
	180	const struct can_bittiming *dbt,
	181	u32 *ctrlmode, u32 ctrlmode_supported)
c25cc799	182
da45a1e4 VM	183	{
da45a1e4 VM	184	if (!tdc_const \|\| !(ctrlmode_supported & CAN_CTRLMODE_TDC_AUTO))
c25cc799 VM	185	return;
c25cc799 VM	186
da45a1e4	187	*ctrlmode &= ~CAN_CTRLMODE_TDC_MASK;
63dfe070	188
c25cc799 VM	189	/* As specified in ISO 11898-1 section 11.3.3 "Transmitter
	190	* delay compensation" (TDC) is only applicable if data BRP is
	191	* one or two.
	192	*/
	193	if (dbt->brp == 1 \|\| dbt->brp == 2) {
39f66c9e VM	194	/* Sample point in clock periods */
	195	u32 sample_point_in_tc = (CAN_SYNC_SEG + dbt->prop_seg +
	196	dbt->phase_seg1) * dbt->brp;
c25cc799	197
39f66c9e	198	if (sample_point_in_tc < tdc_const->tdco_min)
63dfe070	199	return;
39f66c9e	200	tdc->tdco = min(sample_point_in_tc, tdc_const->tdco_max);
da45a1e4	201	*ctrlmode \|= CAN_CTRLMODE_TDC_AUTO;
c25cc799 VM	202	}
c25cc799 VM	203	}
5a9d5ecd MKB	204	#endif /* CONFIG_CAN_CALC_BITTIMING */
	205
	206	/* Checks the validity of the specified bit-timing parameters prop_seg,
	207	* phase_seg1, phase_seg2 and sjw and tries to determine the bitrate
	208	* prescaler value brp. You can find more information in the header
	209	* file linux/can/netlink.h.
	210	*/
5597f082	211	static int can_fixup_bittiming(const struct net_device dev, struct can_bittiming bt,
5a9d5ecd MKB	212	const struct can_bittiming_const *btc)
5a9d5ecd MKB	213	{
5597f082	214	const struct can_priv *priv = netdev_priv(dev);
e3462904	215	unsigned int tseg1, alltseg;
5a9d5ecd MKB	216	u64 brp64;
	217
	218	tseg1 = bt->prop_seg + bt->phase_seg1;
	219	if (!bt->sjw)
	220	bt->sjw = 1;
	221	if (bt->sjw > btc->sjw_max \|\|
	222	tseg1 < btc->tseg1_min \|\| tseg1 > btc->tseg1_max \|\|
	223	bt->phase_seg2 < btc->tseg2_min \|\| bt->phase_seg2 > btc->tseg2_max)
	224	return -ERANGE;
	225
	226	brp64 = (u64)priv->clock.freq * (u64)bt->tq;
	227	if (btc->brp_inc > 1)
	228	do_div(brp64, btc->brp_inc);
	229	brp64 += 500000000UL - 1;
	230	do_div(brp64, 1000000000UL); /* the practicable BRP */
	231	if (btc->brp_inc > 1)
	232	brp64 *= btc->brp_inc;
	233	bt->brp = (u32)brp64;
	234
	235	if (bt->brp < btc->brp_min \|\| bt->brp > btc->brp_max)
	236	return -EINVAL;
	237
	238	alltseg = bt->prop_seg + bt->phase_seg1 + bt->phase_seg2 + 1;
	239	bt->bitrate = priv->clock.freq / (bt->brp * alltseg);
	240	bt->sample_point = ((tseg1 + 1) * 1000) / alltseg;
	241
	242	return 0;
	243	}
	244
	245	/* Checks the validity of predefined bitrate settings */
	246	static int
5597f082	247	can_validate_bitrate(const struct net_device dev, const struct can_bittiming bt,
5a9d5ecd MKB	248	const u32 *bitrate_const,
	249	const unsigned int bitrate_const_cnt)
	250	{
5a9d5ecd MKB	251	unsigned int i;
	252
	253	for (i = 0; i < bitrate_const_cnt; i++) {
	254	if (bt->bitrate == bitrate_const[i])
5b60d334	255	return 0;
5a9d5ecd MKB	256	}
5a9d5ecd MKB	257
5b60d334	258	return -EINVAL;
5a9d5ecd MKB	259	}
5a9d5ecd MKB	260
5597f082	261	int can_get_bittiming(const struct net_device dev, struct can_bittiming bt,
5a9d5ecd MKB	262	const struct can_bittiming_const *btc,
	263	const u32 *bitrate_const,
	264	const unsigned int bitrate_const_cnt)
	265	{
	266	int err;
	267
	268	/* Depending on the given can_bittiming parameter structure the CAN
	269	* timing parameters are calculated based on the provided bitrate OR
	270	* alternatively the CAN timing parameters (tq, prop_seg, etc.) are
	271	* provided directly which are then checked and fixed up.
	272	*/
	273	if (!bt->tq && bt->bitrate && btc)
	274	err = can_calc_bittiming(dev, bt, btc);
	275	else if (bt->tq && !bt->bitrate && btc)
	276	err = can_fixup_bittiming(dev, bt, btc);
	277	else if (!bt->tq && bt->bitrate && bitrate_const)
	278	err = can_validate_bitrate(dev, bt, bitrate_const,
	279	bitrate_const_cnt);
	280	else
	281	err = -EINVAL;
	282
	283	return err;
	284	}