diff options
| -rw-r--r-- | drivers/net/can/m_can/m_can.c | 46 |
1 files changed, 43 insertions, 3 deletions
diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c index f4947a74b65f..79dd3c36ea32 100644 --- a/drivers/net/can/m_can/m_can.c +++ b/drivers/net/can/m_can/m_can.c @@ -126,6 +126,12 @@ enum m_can_mram_cfg { #define DBTP_DSJW_SHIFT 0 #define DBTP_DSJW_MASK (0xf << DBTP_DSJW_SHIFT) +/* Transmitter Delay Compensation Register (TDCR) */ +#define TDCR_TDCO_SHIFT 8 +#define TDCR_TDCO_MASK (0x7F << TDCR_TDCO_SHIFT) +#define TDCR_TDCF_SHIFT 0 +#define TDCR_TDCF_MASK (0x7F << TDCR_TDCF_SHIFT) + /* Test Register (TEST) */ #define TEST_LBCK BIT(4) @@ -987,13 +993,47 @@ static int m_can_set_bittiming(struct net_device *dev) m_can_write(priv, M_CAN_NBTP, reg_btp); if (priv->can.ctrlmode & CAN_CTRLMODE_FD) { + reg_btp = 0; brp = dbt->brp - 1; sjw = dbt->sjw - 1; tseg1 = dbt->prop_seg + dbt->phase_seg1 - 1; tseg2 = dbt->phase_seg2 - 1; - reg_btp = (brp << DBTP_DBRP_SHIFT) | (sjw << DBTP_DSJW_SHIFT) | - (tseg1 << DBTP_DTSEG1_SHIFT) | - (tseg2 << DBTP_DTSEG2_SHIFT); + + /* TDC is only needed for bitrates beyond 2.5 MBit/s. + * This is mentioned in the "Bit Time Requirements for CAN FD" + * paper presented at the International CAN Conference 2013 + */ + if (dbt->bitrate > 2500000) { + u32 tdco, ssp; + + /* Use the same value of secondary sampling point + * as the data sampling point + */ + ssp = dbt->sample_point; + + /* Equation based on Bosch's M_CAN User Manual's + * Transmitter Delay Compensation Section + */ + tdco = (priv->can.clock.freq / 1000) * + ssp / dbt->bitrate; + + /* Max valid TDCO value is 127 */ + if (tdco > 127) { + netdev_warn(dev, "TDCO value of %u is beyond maximum. Using maximum possible value\n", + tdco); + tdco = 127; + } + + reg_btp |= DBTP_TDC; + m_can_write(priv, M_CAN_TDCR, + tdco << TDCR_TDCO_SHIFT); + } + + reg_btp |= (brp << DBTP_DBRP_SHIFT) | + (sjw << DBTP_DSJW_SHIFT) | + (tseg1 << DBTP_DTSEG1_SHIFT) | + (tseg2 << DBTP_DTSEG2_SHIFT); + m_can_write(priv, M_CAN_DBTP, reg_btp); } |