drivers/net/can/dev/bittiming.c

   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
   7 #include <linux/can/dev.h>
   8
   9 void can_sjw_set_default(struct can_bittiming *bt)
  10 {
  11         if (bt->sjw)
  12                 return;
  13
  14         /* If user space provides no sjw, use sane default of phase_seg2 / 2 */
  15         bt->sjw = max(1U, min(bt->phase_seg1, bt->phase_seg2 / 2));
  16 }
  17
  18 int can_sjw_check(const struct net_device *dev, const struct can_bittiming *bt,
  19                   const struct can_bittiming_const *btc, struct netlink_ext_ack *extack)
  20 {
  21         if (bt->sjw > btc->sjw_max) {
  22                 NL_SET_ERR_MSG_FMT(extack, "sjw: %u greater than max sjw: %u",
  23                                    bt->sjw, btc->sjw_max);
  24                 return -EINVAL;
  25         }
  26
  27         if (bt->sjw > bt->phase_seg1) {
  28                 NL_SET_ERR_MSG_FMT(extack,
  29                                    "sjw: %u greater than phase-seg1: %u",
  30                                    bt->sjw, bt->phase_seg1);
  31                 return -EINVAL;
  32         }
  33
  34         if (bt->sjw > bt->phase_seg2) {
  35                 NL_SET_ERR_MSG_FMT(extack,
  36                                    "sjw: %u greater than phase-seg2: %u",
  37                                    bt->sjw, bt->phase_seg2);
  38                 return -EINVAL;
  39         }
  40
  41         return 0;
  42 }
  43
  44 /* Checks the validity of the specified bit-timing parameters prop_seg,
  45  * phase_seg1, phase_seg2 and sjw and tries to determine the bitrate
  46  * prescaler value brp. You can find more information in the header
  47  * file linux/can/netlink.h.
  48  */
  49 static int can_fixup_bittiming(const struct net_device *dev, struct can_bittiming *bt,
  50                                const struct can_bittiming_const *btc,
  51                                struct netlink_ext_ack *extack)
  52 {
  53         const unsigned int tseg1 = bt->prop_seg + bt->phase_seg1;
  54         const struct can_priv *priv = netdev_priv(dev);
  55         u64 brp64;
  56         int err;
  57
  58         if (tseg1 < btc->tseg1_min) {
  59                 NL_SET_ERR_MSG_FMT(extack, "prop-seg + phase-seg1: %u less than tseg1-min: %u",
  60                                    tseg1, btc->tseg1_min);
  61                 return -EINVAL;
  62         }
  63         if (tseg1 > btc->tseg1_max) {
  64                 NL_SET_ERR_MSG_FMT(extack, "prop-seg + phase-seg1: %u greater than tseg1-max: %u",
  65                                    tseg1, btc->tseg1_max);
  66                 return -EINVAL;
  67         }
  68         if (bt->phase_seg2 < btc->tseg2_min) {
  69                 NL_SET_ERR_MSG_FMT(extack, "phase-seg2: %u less than tseg2-min: %u",
  70                                    bt->phase_seg2, btc->tseg2_min);
  71                 return -EINVAL;
  72         }
  73         if (bt->phase_seg2 > btc->tseg2_max) {
  74                 NL_SET_ERR_MSG_FMT(extack, "phase-seg2: %u greater than tseg2-max: %u",
  75                                    bt->phase_seg2, btc->tseg2_max);
  76                 return -EINVAL;
  77         }
  78
  79         can_sjw_set_default(bt);
  80
  81         err = can_sjw_check(dev, bt, btc, extack);
  82         if (err)
  83                 return err;
  84
  85         brp64 = (u64)priv->clock.freq * (u64)bt->tq;
  86         if (btc->brp_inc > 1)
  87                 do_div(brp64, btc->brp_inc);
  88         brp64 += 500000000UL - 1;
  89         do_div(brp64, 1000000000UL); /* the practicable BRP */
  90         if (btc->brp_inc > 1)
  91                 brp64 *= btc->brp_inc;
  92         bt->brp = (u32)brp64;
  93
  94         if (bt->brp < btc->brp_min) {
  95                 NL_SET_ERR_MSG_FMT(extack, "resulting brp: %u less than brp-min: %u",
  96                                    bt->brp, btc->brp_min);
  97                 return -EINVAL;
  98         }
  99         if (bt->brp > btc->brp_max) {
 100                 NL_SET_ERR_MSG_FMT(extack, "resulting brp: %u greater than brp-max: %u",
 101                                    bt->brp, btc->brp_max);
 102                 return -EINVAL;
 103         }
 104
 105         bt->bitrate = priv->clock.freq / (bt->brp * can_bit_time(bt));
 106         bt->sample_point = ((CAN_SYNC_SEG + tseg1) * 1000) / can_bit_time(bt);
 107         bt->tq = DIV_U64_ROUND_CLOSEST(mul_u32_u32(bt->brp, NSEC_PER_SEC),
 108                                        priv->clock.freq);
 109
 110         return 0;
 111 }
 112
 113 /* Checks the validity of predefined bitrate settings */
 114 static int
 115 can_validate_bitrate(const struct net_device *dev, const struct can_bittiming *bt,
 116                      const u32 *bitrate_const,
 117                      const unsigned int bitrate_const_cnt,
 118                      struct netlink_ext_ack *extack)
 119 {
 120         unsigned int i;
 121
 122         for (i = 0; i < bitrate_const_cnt; i++) {
 123                 if (bt->bitrate == bitrate_const[i])
 124                         return 0;
 125         }
 126
 127         NL_SET_ERR_MSG_FMT(extack, "bitrate %u bps not supported",
 128                            bt->brp);
 129
 130         return -EINVAL;
 131 }
 132
 133 int can_get_bittiming(const struct net_device *dev, struct can_bittiming *bt,
 134                       const struct can_bittiming_const *btc,
 135                       const u32 *bitrate_const,
 136                       const unsigned int bitrate_const_cnt,
 137                       struct netlink_ext_ack *extack)
 138 {
 139         /* Depending on the given can_bittiming parameter structure the CAN
 140          * timing parameters are calculated based on the provided bitrate OR
 141          * alternatively the CAN timing parameters (tq, prop_seg, etc.) are
 142          * provided directly which are then checked and fixed up.
 143          */
 144         if (!bt->tq && bt->bitrate && btc)
 145                 return can_calc_bittiming(dev, bt, btc, extack);
 146         if (bt->tq && !bt->bitrate && btc)
 147                 return can_fixup_bittiming(dev, bt, btc, extack);
 148         if (!bt->tq && bt->bitrate && bitrate_const)
 149                 return can_validate_bitrate(dev, bt, bitrate_const,
 150                                             bitrate_const_cnt, extack);
 151
 152         return -EINVAL;
 153 }