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Date: Thu, 9 Jun 2022 17:55:34 +0900
From: Vincent Mailhol <vincent.mailhol@...il.com>
To: Marc Kleine-Budde <mkl@...gutronix.de>
Cc: Srinivas Neeli <srinivas.neeli@...inx.com>, wg@...ndegger.com,
davem@...emloft.net, edumazet@...gle.com, srinivas.neeli@....com,
neelisrinivas18@...il.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
Subject: Re: [PATCH V3 2/2] can: xilinx_can: Add Transmitter delay
compensation (TDC) feature support
On Thu. 9 juin 2022 at 17:34, Marc Kleine-Budde <mkl@...gutronix.de> wrote:
> On 09.06.2022 13:54:33, 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
> > CANFD controllers, will compensate for the measure loop delay in
> > the receive path.
> >
> > Signed-off-by: Srinivas Neeli <srinivas.neeli@...inx.com>
> > ---
> > Changes in V3:
> > -Implemented GENMASK,FIELD_PERP & FIELD_GET Calls.
> > -Implemented TDC feature for all Xilinx CANFD controllers.
> > -corrected prescalar to prescaler(typo).
> > Changes in V2:
> > -Created two patchs one for revert another for TDC support.
> > ---
> > drivers/net/can/xilinx_can.c | 48 ++++++++++++++++++++++++++++++++----
> > 1 file changed, 43 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/net/can/xilinx_can.c b/drivers/net/can/xilinx_can.c
> > index e179d311aa28..288be69c0aed 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
> > *
> > @@ -9,6 +9,7 @@
> > * This driver is developed for Axi CAN IP and for Zynq CANPS Controller.
> > */
> >
> > +#include <linux/bitfield.h>
> > #include <linux/clk.h>
> > #include <linux/errno.h>
> > #include <linux/init.h>
> > @@ -99,6 +100,7 @@ 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 GENMASK(22, 16) /* 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 +134,8 @@ 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 GENMASK(13, 8) /* Transmitter Delay Compensation Offset */
> ^^^^^
> This is a MASK.
>
> > +#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 */
> > @@ -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
> > @@ -405,7 +419,7 @@ static int xcan_set_bittiming(struct net_device *ndev)
> > return -EPERM;
> > }
> >
> > - /* Setting Baud Rate prescalar value in BRPR Register */
> > + /* Setting Baud Rate prescaler value in BRPR Register */
>
> unrelated change, please make it a separate patch
>
> > btr0 = (bt->brp - 1);
> >
> > /* Setting Time Segment 1 in BTR Register */
> > @@ -422,8 +436,12 @@ static int xcan_set_bittiming(struct net_device *ndev)
> >
> > if (priv->devtype.cantype == XAXI_CANFD ||
> > priv->devtype.cantype == XAXI_CANFD_2_0) {
> > - /* Setting Baud Rate prescalar value in F_BRPR Register */
> > + /* Setting Baud Rate prescaler value in F_BRPR Register */
>
> same
>
> > btr0 = dbt->brp - 1;
> > + if (can_tdc_is_enabled(&priv->can))
> > + btr0 |=
> > + FIELD_PREP(XCAN_BRPR_TDCO_SHIFT, priv->can.tdc.tdco) |
> > + XCAN_BRPR_TDC_ENABLE;
> >
> > /* Setting Time Segment 1 in BTR Register */
> > btr1 = dbt->prop_seg + dbt->phase_seg1 - 1;
> > @@ -1483,6 +1501,22 @@ 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 = FIELD_GET(XCAN_SR_TDCV_MASK, priv->read_reg(priv, XCAN_SR_OFFSET));
> > +
> > + return 0;
> > +}
> > +
> > static const struct net_device_ops xcan_netdev_ops = {
> > .ndo_open = xcan_open,
> > .ndo_stop = xcan_close,
> > @@ -1744,8 +1778,12 @@ static int xcan_probe(struct platform_device *pdev)
> > &xcan_data_bittiming_const_canfd2;
> >
> > if (devtype->cantype == XAXI_CANFD ||
> > - devtype->cantype == XAXI_CANFD_2_0)
> > - priv->can.ctrlmode_supported |= CAN_CTRLMODE_FD;
> > + devtype->cantype == XAXI_CANFD_2_0) {
> > + priv->can.ctrlmode_supported |= CAN_CTRLMODE_FD |
> > + CAN_CTRLMODE_TDC_AUTO;
> > + priv->can.do_get_auto_tdcv = xcan_get_auto_tdcv;
> > + priv->can.tdc_const = &xcan_tdc_const;
> > + }
> >
> > priv->reg_base = addr;
> > priv->tx_max = tx_max;
> > --
> > 2.25.1
> >
> >
>
> Otherwise looks good.
Same for me. Also, thanks for using the TDC framework. You are the
first one to use it after I created it!
Assuming you address all of Marc’s comment, please add this in your v4:
Reviewed-by: Vincent Mailhol <mailhol.vincent@...adoo.fr>
Yours sincerely,
Vincent Mailhol
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