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SubjectRe: [PATCH v4 1/1] can: ucan: add driver for Theobroma Systems UCAN devices
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Hello Jacob,

just a few minor issues and a question about bus-off handling...

Am 03.04.2018 um 16:35 schrieb Jakob Unterwurzacher:
> The UCAN driver supports the microcontroller-based USB/CAN
> adapters from Theobroma Systems. There are two form-factors
> that run essentially the same firmware:
>
> * Seal: standalone USB stick ( https://www.theobroma-systems.com/seal )
>
> * Mule: integrated on the PCB of various System-on-Modules from
> Theobroma Systems like the A31-µQ7 and the RK3399-Q7
> ( https://www.theobroma-systems.com/rk3399-q7 )
>
> The USB wire protocol has been designed to be as generic and
> hardware-indendent as possible in the hope of being useful for
> implementation on other microcontrollers.
>
> Signed-off-by: Martin Elshuber <martin.elshuber@theobroma-systems.com>
> Signed-off-by: Jakob Unterwurzacher <jakob.unterwurzacher@theobroma-systems.com>
> Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
> ---
> Documentation/networking/can_ucan_protocol.rst | 315 +++++
> Documentation/networking/index.rst | 1 +
> drivers/net/can/usb/Kconfig | 10 +
> drivers/net/can/usb/Makefile | 1 +
> drivers/net/can/usb/ucan.c | 1596 ++++++++++++++++++++++++
> 5 files changed, 1923 insertions(+)
> create mode 100644 Documentation/networking/can_ucan_protocol.rst
> create mode 100644 drivers/net/can/usb/ucan.c
>
[..snip..]

> diff --git a/drivers/net/can/usb/Kconfig b/drivers/net/can/usb/Kconfig
> index c36f4bdcbf4f..490cdce1f1da 100644
> --- a/drivers/net/can/usb/Kconfig
> +++ b/drivers/net/can/usb/Kconfig
> @@ -89,4 +89,14 @@ config CAN_MCBA_USB
> This driver supports the CAN BUS Analyzer interface
> from Microchip (http://www.microchip.com/development-tools/).
>
> +config CAN_UCAN
> + tristate "Theobroma Systems UCAN interface"
> + ---help---
> + This driver supports the Theobroma Systems
> + UCAN USB-CAN interface.
> +
> + UCAN is an microcontroller-based USB-CAN interface that
> + is integrated on System-on-Modules made by Theobroma Systems
> + (https://www.theobroma-systems.com/som-products).
> +
> endmenu
> diff --git a/drivers/net/can/usb/Makefile b/drivers/net/can/usb/Makefile
> index 49ac7b99ba32..4176e8358232 100644
> --- a/drivers/net/can/usb/Makefile
> +++ b/drivers/net/can/usb/Makefile
> @@ -10,3 +10,4 @@ obj-$(CONFIG_CAN_KVASER_USB) += kvaser_usb.o
> obj-$(CONFIG_CAN_PEAK_USB) += peak_usb/
> obj-$(CONFIG_CAN_8DEV_USB) += usb_8dev.o
> obj-$(CONFIG_CAN_MCBA_USB) += mcba_usb.o
> +obj-$(CONFIG_CAN_UCAN) += ucan.o
> diff --git a/drivers/net/can/usb/ucan.c b/drivers/net/can/usb/ucan.c
> new file mode 100644
> index 000000000000..bb2d62dcbd7b
> --- /dev/null
> +++ b/drivers/net/can/usb/ucan.c
> @@ -0,0 +1,1596 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +/* Driver for Theobroma Systems UCAN devices, Protocol Version 3
> + *
> + * Copyright (C) 2018 Theobroma Systems Design und Consulting GmbH
> + *
> + *
> + * General Description:
> + *
> + * The USB Device uses three Endpoints:
> + *
> + * CONTROL Endpoint: Is used the setup the device (start, stop,
> + * info, configure).
> + *
> + * IN Endpoint: The device sends CAN Frame Messages and Device
> + * Information using the IN endpoint.
> + *
> + * OUT Endpoint: The driver sends configuration requests, and CAN
> + * Frames on the out endpoint.
> + *
> + * Error Handling:
> + *
> + * If error reporting is turned on the device encodes error into CAN
> + * error frames (see uapi/linux/can/error.h) and sends it using the
> + * IN Endpoint. The driver updates statistics and forward it.
> + */
> +
> +#include <linux/can.h>

[...snip...]

> +static struct ucan_urb_context *ucan_alloc_context(struct ucan_priv *up)
> +{
> + int i;
> + unsigned long flags;
> + struct ucan_urb_context *ret = NULL;
> +
> + if (WARN_ON_ONCE(!up->context_array))
> + return NULL;
> +
> + /* execute context operation atomically */
> + spin_lock_irqsave(&up->context_lock, flags);
> +
> + for (i = 0; i < up->device_info.tx_fifo; i++) {
> + if (!up->context_array[i].allocated) {
> + /* update context */
> + ret = &up->context_array[i];
> + up->context_array[i].allocated = true;
> +
> + /* stop queue if necessary */
> + up->available_tx_urbs--;
> + if (!up->available_tx_urbs)
> + netif_stop_queue(up->netdev);
> +
> + goto done_restore;

break instead of goto!?

> + }
> + }
> +
> +done_restore:
> + spin_unlock_irqrestore(&up->context_lock, flags);
> + return ret;
> +}
> +
> +static bool ucan_release_context(struct ucan_priv *up,
> + struct ucan_urb_context *ctx)
> +{
> + unsigned long flags;
> + bool ret = false;
> +
> + if (WARN_ON_ONCE(!up->context_array))
> + return false;
> +
> + /* execute context operation atomically */
> + spin_lock_irqsave(&up->context_lock, flags);
> +
> + /* context was not allocated, maybe the device sent garbage */
> + if (!ctx->allocated)
> + goto done_restore;

if (ctx->allocated) {

> + ctx->allocated = false;
> +
> + /* check if the queue needs to be woken */
> + if (!up->available_tx_urbs)
> + netif_wake_queue(up->netdev);
> + up->available_tx_urbs++;
> +

}
> +done_restore:

No need for a label.

> + spin_unlock_irqrestore(&up->context_lock, flags);
> + return ret;

Hm, what is "ret" good for? The value is always "false".

Maybe it's better to print an error message here and make
this function void.

> +}

[...snip...]

> +/* Handle a CAN error frame that we have received from the device.
> + * Returns true if the can state has changed.
> + */
> +static bool ucan_handle_error_frame(struct ucan_priv *up,
> + struct ucan_message_in *m,
> + canid_t canid)
> +{
> + enum can_state new_state = up->can.state;
> + struct net_device_stats *net_stats = &up->netdev->stats;
> + struct can_device_stats *can_stats = &up->can.can_stats;
> +
> + if (canid & CAN_ERR_LOSTARB)
> + can_stats->arbitration_lost++;
> +
> + if (canid & CAN_ERR_BUSERROR)
> + can_stats->bus_error++;
> +
> + if (canid & CAN_ERR_ACK)
> + net_stats->tx_errors++;
> +
> + if (canid & CAN_ERR_BUSOFF)
> + new_state = CAN_STATE_BUS_OFF;
> +
> + /* controller problems, details in data[1] */
> + if (canid & CAN_ERR_CRTL) {
> + u8 d1 = m->msg.can_msg.data[1];
> +
> + if (d1 & CAN_ERR_CRTL_RX_OVERFLOW)
> + net_stats->rx_over_errors++;
> +
> + /* controller state bits: if multiple are set the worst wins */
> + if (d1 & CAN_ERR_CRTL_ACTIVE)
> + new_state = CAN_STATE_ERROR_ACTIVE;
> +
> + if (d1 & (CAN_ERR_CRTL_RX_WARNING | CAN_ERR_CRTL_TX_WARNING))
> + new_state = CAN_STATE_ERROR_WARNING;
> +
> + if (d1 & (CAN_ERR_CRTL_RX_PASSIVE | CAN_ERR_CRTL_TX_PASSIVE))
> + new_state = CAN_STATE_ERROR_PASSIVE;
> + }
> +
> + /* protocol error, details in data[2] */
> + if (canid & CAN_ERR_PROT) {
> + u8 d2 = m->msg.can_msg.data[2];
> +
> + if (d2 & CAN_ERR_PROT_TX)
> + net_stats->tx_errors++;
> + else
> + net_stats->rx_errors++;
> + }
> +
> + /* no state change - we are done */
> + if (up->can.state == new_state)
> + return false;
> +
> + /* we switched into a better state */
> + if (up->can.state > new_state) {
> + up->can.state = new_state;
> + return true;
> + }
> +
> + /* we switched into a worse state */
> + up->can.state = new_state;
> + switch (new_state) {
> + case CAN_STATE_BUS_OFF:
> + can_stats->bus_off++;
> + can_bus_off(up->netdev);

How does the CAN controller firmware handle bus-off? Does it recover
automatically? "can_bus_off()" will restart the CAN controller after
"restart-ms" or manually via netlink "restart" command by calling
"ucan_set_mode(CAN_START_MODE)":

# ip link set canX type can restart-ms 100
# ip link set canX type can restart

See also:

https://elixir.bootlin.com/linux/latest/source/drivers/net/can/dev.c#L597

> + netdev_info(up->netdev, "link has gone into BUS-OFF state\n");

"can_bus_off()" already prints a message.

> + break;
> + case CAN_STATE_ERROR_PASSIVE:
> + can_stats->error_passive++;
> + break;
> + case CAN_STATE_ERROR_WARNING:
> + can_stats->error_warning++;
> + break;
> + default:
> + break;
> + }
> + return true;
> +}
> +
> +/* Callback on reception of a can frame via the IN endpoint
> + *
> + * This function allocates an skb and transferres it to the Linux
> + * network stack
> + */
> +static void ucan_rx_can_msg(struct ucan_priv *up, struct ucan_message_in *m)
> +{
> + int len;
> + canid_t canid;
> + struct can_frame *cf;
> + struct sk_buff *skb;
> + struct net_device_stats *stats = &up->netdev->stats;
> +
> + /* get the contents of the length field */
> + len = le16_to_cpu(m->len);
> +
> + /* check sanity */
> + if (len < UCAN_IN_HDR_SIZE + sizeof(m->msg.can_msg.id)) {
> + netdev_warn(up->netdev, "invalid input message len: %d\n", len);
> + return;
> + }
> +
> + /* handle error frames */
> + canid = le32_to_cpu(m->msg.can_msg.id);
> + if (canid & CAN_ERR_FLAG) {
> + bool busstate_changed = ucan_handle_error_frame(up, m, canid);
> +
> + /* if berr-reporting is off only state changes get through */
> + if (!(up->can.ctrlmode & CAN_CTRLMODE_BERR_REPORTING) &&
> + !busstate_changed)
> + return;
> + } else {
> + canid_t canid_mask;
> + /* compute the mask for canid */
> + canid_mask = CAN_RTR_FLAG;
> + if (canid & CAN_EFF_FLAG)
> + canid_mask |= CAN_EFF_MASK | CAN_EFF_FLAG;
> + else
> + canid_mask |= CAN_SFF_MASK;
> +
> + if (canid & ~canid_mask)
> + netdev_warn(up->netdev,
> + "masking unexpected set bits in canid (canid %x, mask %x)",

Line too long... there are a few more lines exceeding 80 chars.

> + canid, canid_mask);
> +
> + canid &= canid_mask;
> + }
> +
> + /* allocate skb */
> + skb = alloc_can_skb(up->netdev, &cf);
> + if (!skb)
> + return;
> +
> + /* fill the can frame */
> + cf->can_id = canid;
> +
> + /* compute DLC taking RTR_FLAG into account */
> + cf->can_dlc = ucan_get_can_dlc(&m->msg.can_msg, len);
> +
> + /* copy the payload of non RTR frames */
> + if (!(cf->can_id & CAN_RTR_FLAG) || (cf->can_id & CAN_ERR_FLAG))
> + memcpy(cf->data, m->msg.can_msg.data, cf->can_dlc);
> +
> + /* don't count error frames as real packets */
> + stats->rx_packets++;
> + stats->rx_bytes += cf->can_dlc;
> +
> + /* pass it to Linux */
> + netif_rx(skb);
> +}

[...snip...]

You may also want to replace

it (ret)
goto err;

with

return ret;

in "ucan_open()" and "ucan_probe()".

You can then add my:

Acked-by: Wolfgang Grandegger <wg@grandegger.com>

Thanks for your contribution!

Wolfgang.

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