Message-ID: <20260123-lush-cryptic-parrot-ea322c-mkl@pengutronix.de>
Date: Fri, 23 Jan 2026 14:52:19 +0100
From: Marc Kleine-Budde <mkl@...gutronix.de>
To: Arun Muthusamy <arun.muthusamy@...sler.com>
Cc: robh@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org, 
	mailhol@...nel.org, devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-can@...r.kernel.org, Daniel Hellstrom <daniel@...sler.com>
Subject: Re: [PATCH v3 07/15] can: grcan: add FD capability detection and
 nominal bit-timing

On 22.01.2026 13:10:30, Arun Muthusamy wrote:
> Add capability for the driver to detect CAN FD support
> and adjust accordingly. Introduce structures and functions
> for setting nominal bit-timing for standard CAN FD.
> The `grcan_hwcap` structure defines hardware capabilities like
> CAN FD support and baud-rate options. Additionally, improved
> device tree compatibility by updating the `of_device_id` table
> for better matching of GRCAN and GRCANFD devices. Also update
> Kconfig to mention GRCANFD support.
>
> Signed-off-by: Arun Muthusamy <arun.muthusamy@...sler.com>
> Signed-off-by: Daniel Hellstrom <daniel@...sler.com>
> ---
>  drivers/net/can/Kconfig |   6 +-
>  drivers/net/can/grcan.c | 142 +++++++++++++++++++++++++++++++++++-----
>  2 files changed, 130 insertions(+), 18 deletions(-)
>
> diff --git a/drivers/net/can/Kconfig b/drivers/net/can/Kconfig
> index d43d56694667..96f61b40a898 100644
> --- a/drivers/net/can/Kconfig
> +++ b/drivers/net/can/Kconfig
> @@ -133,10 +133,12 @@ config CAN_FLEXCAN
>  	  Say Y here if you want to support for Freescale FlexCAN.
>
>  config CAN_GRCAN
> -	tristate "Aeroflex Gaisler GRCAN and GRHCAN CAN devices"
> +	tristate "Aeroflex Gaisler GRCAN(FD) and GRHCAN CAN devices"
>  	depends on OF && HAS_DMA && HAS_IOMEM
>  	help
> -	  Say Y here if you want to use Aeroflex Gaisler GRCAN or GRHCAN.
> +	  Say Y here if you want to use Aeroflex Gaisler GRCAN or GRCANFD
> +	  or GRHCAN.
> +
>  	  Note that the driver supports little endian, even though little
>  	  endian syntheses of the cores would need some modifications on
>  	  the hardware level to work.
> diff --git a/drivers/net/can/grcan.c b/drivers/net/can/grcan.c
> index 5a63d0a0365f..5d09f61a153c 100644
> --- a/drivers/net/can/grcan.c
> +++ b/drivers/net/can/grcan.c
> @@ -33,6 +33,7 @@
>  #include <linux/platform_device.h>
>  #include <linux/spinlock.h>
>  #include <linux/of.h>
> +#include <linux/of_device.h>
>  #include <linux/of_irq.h>
>  #include <linux/clk.h>
>  #include <linux/dma-mapping.h>
> @@ -51,7 +52,11 @@ struct grcan_registers {
>  	u32 __reserved1[GRCAN_RESERVE_SIZE(0x08, 0x18)];
>  	u32 smask;	/* 0x18 - CanMASK */
>  	u32 scode;	/* 0x1c - CanCODE */
> -	u32 __reserved2[GRCAN_RESERVE_SIZE(0x1c, 0x100)];
> +	u32 __reserved2[GRCAN_RESERVE_SIZE(0x1c, 0x40)];
> +	u32 nbtr;	/* 0x40 */
> +	u32 fdbtr;	/* 0x44 */
> +	u32 tdelay;	/* 0x48 */
> +	u32 __reserved2_[GRCAN_RESERVE_SIZE(0x48, 0x100)];
>  	u32 pimsr;	/* 0x100 */
>  	u32 pimr;	/* 0x104 */
>  	u32 pisr;	/* 0x108 */
> @@ -203,6 +208,39 @@ struct grcan_registers {
>  #error "Invalid default buffer size"
>  #endif
>
> +#define GRCANFD_NBTR_SCALER     GENMASK(23, 16)
> +#define GRCANFD_NBTR_PS1        GENMASK(17, 10)
> +#define GRCANFD_NBTR_PS2        GENMASK(9, 5)
> +#define GRCANFD_NBTR_SJW        GENMASK(4, 0)
> +#define GRCANFD_NBTR_TIMING						\
> +	(GRCANFD_NBTR_SCALER | GRCANFD_NBTR_PS1 | GRCANFD_NBTR_PS2 |	\
> +	 GRCANFD_NBTR_SJW)
> +
> +#define GRCANFD_FDBTR_SCALER 0x00ff0000
> +#define GRCANFD_FDBTR_PS1 0x00003c00
> +#define GRCANFD_FDBTR_PS2 0x000001e0
> +#define GRCANFD_FDBTR_SJW 0x0000000f
> +#define GRCANFD_FDBTR_TIMING						\
> +	(GRCANFD_FDBTR_SCALER | GRCANFD_FDBTR_PS1 | GRCANFD_FDBTR_PS2 |	\
> +	 GRCANFD_FDBTR_SJW)
> +
> +#define GRCANFD_FDBTR_SCALER_BIT 16
> +#define GRCANFD_FDBTR_PS1_BIT 10
> +#define GRCANFD_FDBTR_PS2_BIT 5
> +#define GRCANFD_FDBTR_SJW_BIT 0
> +
> +/* Hardware capabilities */
> +struct grcan_hwcap {
> +	/* CAN-FD capable, indicates GRCANFD IP.
> +	 * The GRCANFD has different baud-rate registers and extended DMA
> +	 * format to also describe FD-frames.
> +	 */
> +	const struct can_bittiming_const *bt_const;
> +	int (*set_bittiming)(struct net_device *dev);
> +	bool txbug_possible;
> +	bool fd;
> +};
> +
>  struct grcan_dma_buffer {
>  	size_t size;
>  	void *buf;
> @@ -245,6 +283,7 @@ struct grcan_priv {
>  	struct napi_struct napi;
>
>  	struct grcan_registers __iomem *regs;	/* ioremap'ed registers */
> +	const struct grcan_hwcap *hwcap;
>  	struct grcan_device_config config;
>  	struct grcan_dma dma;
>
> @@ -295,6 +334,7 @@ struct grcan_priv {
>  	 */
>  	bool resetting;
>  	bool closing;
> +

Please remove this change

>  };
>
>  /* Wait time for a short wait for ongoing to clear */
> @@ -393,6 +433,19 @@ static const struct can_bittiming_const grcan_bittiming_const = {
>  	.brp_inc	= 1,
>  };
>
> +/* GRCANFD nominal boundaries for baud-rate parameters */
> +static const struct can_bittiming_const grcanfd_bittiming_const = {
> +	.name		= DRV_NAME,
> +	.tseg1_min	= 2,
> +	.tseg1_max	= 63,
> +	.tseg2_min	= 2,
> +	.tseg2_max	= 16,
> +	.sjw_max	= 16,
> +	.brp_min	= 1,
> +	.brp_max	= 256,
> +	.brp_inc	= 1,
> +};
> +
>  static int grcan_set_bittiming(struct net_device *dev)
>  {
>  	struct grcan_priv *priv = netdev_priv(dev);
> @@ -421,6 +474,32 @@ static int grcan_set_bittiming(struct net_device *dev)
>  	return 0;
>  }
>
> +static int grcanfd_set_bittiming(struct net_device *dev)
> +{
> +	struct grcan_priv *priv = netdev_priv(dev);
> +	struct grcan_registers __iomem *regs;
> +	int sjw, ps1, ps2, scaler;
> +	struct can_bittiming *bt;
> +	u32 timing = 0;
> +
> +	regs = priv->regs;
> +	bt = &priv->can.bittiming;
> +
> +	sjw = bt->sjw;
> +	ps1 = (bt->prop_seg + bt->phase_seg1);
> +	ps2 = bt->phase_seg2;
> +	scaler = bt->brp - 1;
> +
> +	timing |= FIELD_PREP(GRCANFD_NBTR_SJW, sjw);
> +	timing |= FIELD_PREP(GRCANFD_NBTR_PS1, ps1);
> +	timing |= FIELD_PREP(GRCANFD_NBTR_PS2, ps2);
> +	timing |= FIELD_PREP(GRCANFD_NBTR_SCALER, scaler);
> +	netdev_info(dev, "setting timing=0x%x\n", timing);

make it debug or remove

> +	grcan_write_bits(&regs->nbtr, timing, GRCANFD_NBTR_TIMING);
> +
> +	return 0;
> +}
> +
>  static int grcan_get_berr_counter(const struct net_device *dev,
>  				  struct can_berr_counter *bec)
>  {
> @@ -1545,7 +1624,8 @@ static const struct ethtool_ops grcan_ethtool_ops = {
>
>  static int grcan_setup_netdev(struct platform_device *ofdev,
>  			      void __iomem *base,
> -			      int irq, u32 ambafreq, bool txbug)
> +			      int irq, u32 ambafreq, bool txbug,
> +			      const struct grcan_hwcap *hwcap)
>  {
>  	struct net_device *dev;
>  	struct grcan_priv *priv;
> @@ -1568,14 +1648,14 @@ static int grcan_setup_netdev(struct platform_device *ofdev,
>  	priv->dev = dev;
>  	priv->ofdev_dev = &ofdev->dev;
>  	priv->regs = base;
> -	priv->can.bittiming_const = &grcan_bittiming_const;
> -	priv->can.do_set_bittiming = grcan_set_bittiming;
> +	priv->can.bittiming_const = hwcap->bt_const;
>  	priv->can.do_set_mode = grcan_set_mode;
>  	priv->can.do_get_berr_counter = grcan_get_berr_counter;
>  	priv->can.clock.freq = ambafreq;
>  	priv->can.ctrlmode_supported =
>  		CAN_CTRLMODE_LISTENONLY | CAN_CTRLMODE_ONE_SHOT;
>  	priv->need_txbug_workaround = txbug;
> +	priv->hwcap = hwcap;
>
>  	/* Discover if triple sampling is supported by hardware */
>  	regs = priv->regs;
> @@ -1620,22 +1700,33 @@ static int grcan_probe(struct platform_device *ofdev)
>  {
>  	struct device_node *np = ofdev->dev.of_node;
>  	struct device_node *sysid_parent;
> +	const struct grcan_hwcap *hwcap;
>  	struct clk *clk;
>  	u32 sysid, ambafreq;
>  	int irq, err;
>  	void __iomem *base;
>  	bool txbug = true;
>
> +	hwcap = device_get_match_data(&ofdev->dev);
> +	if (!hwcap) {
> +		dev_err(&ofdev->dev, "Platform data not provided!\n");
> +		return -ENODEV;
> +	}
> +

All entries in grcan_match have a corresponding data member, so I think
you can remove this check.

[...]

>  static const struct of_device_id grcan_match[] = {
> -	{.name = "GAISLER_GRCAN"},
> -	{.name = "01_03d"},
> -	{.name = "GAISLER_GRHCAN"},
> -	{.name = "01_034"},
> +	{.name = "GAISLER_GRCAN", .data = &grcan_hwcap},
> +	{.name = "01_03d", .data = &grcan_hwcap},
> +	{.name = "GAISLER_GRHCAN", .data = &grcan_hwcap},
> +	{.name = "01_034", .data = &grcan_hwcap},
> +	{.compatible = "gaisler,grcan", .data = &grcan_hwcap},
> +	/* GRCANFD */
> +	{.compatible = "gaisler,grcanfd", .data = &grcanfd_hwcap},
> +	{.name = "GAISLER_GRCANFD", .data = &grcanfd_hwcap},
> +	{.name = "01_0b5", .data = &grcanfd_hwcap},
>  	{},
>  };
>

Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde          |
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