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Message-ID: <20220607091952.gls5bgwplytbhmoq@pengutronix.de>
Date: Tue, 7 Jun 2022 11:19:52 +0200
From: Marc Kleine-Budde <mkl@...gutronix.de>
To: Srinivas Neeli <srinivas.neeli@...inx.com>
Cc: wg@...ndegger.com, davem@...emloft.net, edumazet@...gle.com,
appana.durga.rao@...inx.com, sgoud@...inx.com,
michal.simek@...inx.com, kuba@...nel.org, pabeni@...hat.com,
linux-can@...r.kernel.org, netdev@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
git@...inx.com, Vincent Mailhol <mailhol.vincent@...adoo.fr>
Subject: Re: [PATCH V2 2/2] can: xilinx_can: Add Transmitter delay
compensation (TDC) feature support
Hello Srinivas Neeli,
thanks for your patch!
On 07.06.2022 14:26:54, Srinivas Neeli wrote:
> Added Transmitter delay compensation (TDC) feature support.
> In the case of higher measured loop delay with higher baud rates,
> observed bit stuff errors. By enabling the TDC feature in a controller,
> will compensate for the measure loop delay in the receive path.
Wich controllers support TDC?
XAXI_CANFD doesn't have do_get_auto_tdc assigned, but
CAN_CTRLMODE_TDC_AUTO is set.
> Signed-off-by: Srinivas Neeli <srinivas.neeli@...inx.com>
> ---
> drivers/net/can/xilinx_can.c | 46 +++++++++++++++++++++++++++++++++---
> 1 file changed, 43 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/net/can/xilinx_can.c b/drivers/net/can/xilinx_can.c
> index e179d311aa28..d0edd1bca33c 100644
> --- a/drivers/net/can/xilinx_can.c
> +++ b/drivers/net/can/xilinx_can.c
> @@ -1,7 +1,7 @@
> // SPDX-License-Identifier: GPL-2.0-or-later
> /* Xilinx CAN device driver
> *
> - * Copyright (C) 2012 - 2014 Xilinx, Inc.
> + * Copyright (C) 2012 - 2022 Xilinx, Inc.
> * Copyright (C) 2009 PetaLogix. All rights reserved.
> * Copyright (C) 2017 - 2018 Sandvik Mining and Construction Oy
> *
> @@ -99,6 +99,7 @@ enum xcan_reg {
> #define XCAN_ESR_STER_MASK 0x00000004 /* Stuff error */
> #define XCAN_ESR_FMER_MASK 0x00000002 /* Form error */
> #define XCAN_ESR_CRCER_MASK 0x00000001 /* CRC error */
> +#define XCAN_SR_TDCV_MASK 0x007F0000 /* TDCV Value */
> #define XCAN_SR_TXFLL_MASK 0x00000400 /* TX FIFO is full */
> #define XCAN_SR_ESTAT_MASK 0x00000180 /* Error status */
> #define XCAN_SR_ERRWRN_MASK 0x00000040 /* Error warning */
> @@ -132,6 +133,8 @@ enum xcan_reg {
> #define XCAN_DLCR_BRS_MASK 0x04000000 /* BRS Mask in DLC */
>
> /* CAN register bit shift - XCAN_<REG>_<BIT>_SHIFT */
> +#define XCAN_BRPR_TDCO_SHIFT 8 /* Transmitter Delay Compensation Offset */
> +#define XCAN_BRPR_TDC_ENABLE BIT(16) /* Transmitter Delay Compensation (TDC) Enable */
> #define XCAN_BTR_SJW_SHIFT 7 /* Synchronous jump width */
> #define XCAN_BTR_TS2_SHIFT 4 /* Time segment 2 */
> #define XCAN_BTR_SJW_SHIFT_CANFD 16 /* Synchronous jump width */
> @@ -140,6 +143,7 @@ enum xcan_reg {
> #define XCAN_IDR_ID2_SHIFT 1 /* Extended Message Identifier */
> #define XCAN_DLCR_DLC_SHIFT 28 /* Data length code */
> #define XCAN_ESR_REC_SHIFT 8 /* Rx Error Count */
> +#define XCAN_SR_TDCV_SHIFT 16 /* TDCV Value */
>
> /* CAN frame length constants */
> #define XCAN_FRAME_MAX_DATA_LEN 8
> @@ -276,6 +280,16 @@ static const struct can_bittiming_const xcan_data_bittiming_const_canfd2 = {
> .brp_inc = 1,
> };
>
> +/* Transmission Delay Compensation constants for CANFD2.0 and Versal */
> +static const struct can_tdc_const xcan_tdc_const = {
> + .tdcv_min = 0,
> + .tdcv_max = 0, /* Manual mode not supported. */
> + .tdco_min = 0,
> + .tdco_max = 64,
> + .tdcf_min = 0, /* Filter window not supported */
> + .tdcf_max = 0,
> +};
> +
> /**
> * xcan_write_reg_le - Write a value to the device register little endian
> * @priv: Driver private data structure
> @@ -424,6 +438,11 @@ static int xcan_set_bittiming(struct net_device *ndev)
> priv->devtype.cantype == XAXI_CANFD_2_0) {
> /* Setting Baud Rate prescalar value in F_BRPR Register */
> btr0 = dbt->brp - 1;
> + if (can_tdc_is_enabled(&priv->can)) {
> + btr0 = btr0 |
Make use of "|=" and properly indent.
> + priv->can.tdc.tdco << XCAN_BRPR_TDCO_SHIFT |
Please include <linux/bitfield.h> and make use of "FIELD_PREP".
> + XCAN_BRPR_TDC_ENABLE;
> + }
>
> /* Setting Time Segment 1 in BTR Register */
> btr1 = dbt->prop_seg + dbt->phase_seg1 - 1;
> @@ -1483,6 +1502,23 @@ static int xcan_get_berr_counter(const struct net_device *ndev,
> return 0;
> }
>
> +/**
> + * xcan_get_auto_tdcv - Get Transmitter Delay Compensation Value
> + * @ndev: Pointer to net_device structure
> + * @tdcv: Pointer to TDCV value
> + *
> + * Return: 0 on success
> + */
> +static int xcan_get_auto_tdcv(const struct net_device *ndev, u32 *tdcv)
> +{
> + struct xcan_priv *priv = netdev_priv(ndev);
> +
> + *tdcv = (priv->read_reg(priv, XCAN_SR_OFFSET) & XCAN_SR_TDCV_MASK) >>
> + XCAN_SR_TDCV_SHIFT;
Please use FIELD_GET.
> +
> + return 0;
> +}
> +
> static const struct net_device_ops xcan_netdev_ops = {
> .ndo_open = xcan_open,
> .ndo_stop = xcan_close,
> @@ -1734,18 +1770,22 @@ static int xcan_probe(struct platform_device *pdev)
> priv->can.do_get_berr_counter = xcan_get_berr_counter;
> priv->can.ctrlmode_supported = CAN_CTRLMODE_LOOPBACK |
> CAN_CTRLMODE_BERR_REPORTING;
> + priv->can.do_get_auto_tdcv = xcan_get_auto_tdcv;
I'm not sure, if it has any side effects, if you assign do_get_auto_tdc
for all controllers, even the ones that don't support it. Vincent can
probably clarify this.
>
> if (devtype->cantype == XAXI_CANFD)
> priv->can.data_bittiming_const =
> &xcan_data_bittiming_const_canfd;
>
> - if (devtype->cantype == XAXI_CANFD_2_0)
> + if (devtype->cantype == XAXI_CANFD_2_0) {
> priv->can.data_bittiming_const =
> &xcan_data_bittiming_const_canfd2;
> + priv->can.tdc_const = &xcan_tdc_const;
> + }
>
> if (devtype->cantype == XAXI_CANFD ||
> devtype->cantype == XAXI_CANFD_2_0)
> - priv->can.ctrlmode_supported |= CAN_CTRLMODE_FD;
> + priv->can.ctrlmode_supported |= CAN_CTRLMODE_FD |
> + CAN_CTRLMODE_TDC_AUTO;
>
> priv->reg_base = addr;
> priv->tx_max = tx_max;
regards
Marc
--
Pengutronix e.K. | Marc Kleine-Budde |
Embedded Linux | https://www.pengutronix.de |
Vertretung West/Dortmund | Phone: +49-231-2826-924 |
Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
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