Re: [PATCH v3 2/3] can: kvaser_usb: Utilize all possible tx URBs

[Marc Kleine-Budde <mkl@pengutronix.de>]

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On 03/11/2015 06:39 PM, Ahmed S. Darwish wrote:
> From: Ahmed S. Darwish <ahmed.darwish@valeo.com>
> 
> The driver currently limits the number of outstanding, not yet
> ACKed, transfers to 16 URBs. Meanwhile, the Kvaser firmware
> provides its actual max supported number of outstanding
> transmissions in its reply to the CMD_GET_SOFTWARE_INFO message.
> 
> One example is the UsbCan-II HS/LS device which reports support
> of up to 48 tx URBs instead of just 16, increasing the driver
> throughput by two-fold and reducing the possibility of -ENOBUFs.
> 
> Dynamically set the max tx URBs value according to firmware
> replies.
> 
> Signed-off-by: Ahmed S. Darwish <ahmed.darwish@valeo.com>
> ---
>  drivers/net/can/usb/kvaser_usb.c | 55 +++++++++++++++++++++++++++-------------
>  1 file changed, 37 insertions(+), 18 deletions(-)
> 
> changelog-v3: No changes
> 
> diff --git a/drivers/net/can/usb/kvaser_usb.c b/drivers/net/can/usb/kvaser_usb.c
> index e97a08c..30b4d47 100644
> --- a/drivers/net/can/usb/kvaser_usb.c
> +++ b/drivers/net/can/usb/kvaser_usb.c
> @@ -25,7 +25,6 @@
>  #include <linux/can/dev.h>
>  #include <linux/can/error.h>
>  
> -#define MAX_TX_URBS			16
>  #define MAX_RX_URBS			4
>  #define START_TIMEOUT			1000 /* msecs */
>  #define STOP_TIMEOUT			1000 /* msecs */
> @@ -456,8 +455,13 @@ struct kvaser_usb {
>  	struct usb_endpoint_descriptor *bulk_in, *bulk_out;
>  	struct usb_anchor rx_submitted;
>  
> +	/* @max_tx_urbs: Firmware-reported maximum number of possible
> +	 * outstanding transmissions on this specific Kvaser hardware. The
> +	 * value is also used as a sentinel for marking free URB contexts.
> +	 */
>  	u32 fw_version;
>  	unsigned int nchannels;
> +	unsigned int max_tx_urbs;
>  	enum kvaser_usb_family family;
>  
>  	bool rxinitdone;
> @@ -470,7 +474,7 @@ struct kvaser_usb_net_priv {
>  
>  	spinlock_t tx_contexts_lock;
>  	int active_tx_contexts;
> -	struct kvaser_usb_tx_urb_context tx_contexts[MAX_TX_URBS];
> +	struct kvaser_usb_tx_urb_context *tx_contexts;
>  
>  	struct usb_anchor tx_submitted;
>  	struct completion start_comp, stop_comp;
> @@ -657,9 +661,13 @@ static int kvaser_usb_get_software_info(struct kvaser_usb *dev)
>  	switch (dev->family) {
>  	case KVASER_LEAF:
>  		dev->fw_version = le32_to_cpu(msg.u.leaf.softinfo.fw_version);
> +		dev->max_tx_urbs =
> +			le16_to_cpu(msg.u.leaf.softinfo.max_outstanding_tx);
>  		break;
>  	case KVASER_USBCAN:
>  		dev->fw_version = le32_to_cpu(msg.u.usbcan.softinfo.fw_version);
> +		dev->max_tx_urbs =
> +			le16_to_cpu(msg.u.usbcan.softinfo.max_outstanding_tx);
>  		break;
>  	}
>  
> @@ -715,7 +723,7 @@ static void kvaser_usb_tx_acknowledge(const struct kvaser_usb *dev,
>  
>  	stats = &priv->netdev->stats;
>  
> -	context = &priv->tx_contexts[tid % MAX_TX_URBS];
> +	context = &priv->tx_contexts[tid % dev->max_tx_urbs];
>  
>  	/* Sometimes the state change doesn't come after a bus-off event */
>  	if (priv->can.restart_ms &&
> @@ -744,7 +752,7 @@ static void kvaser_usb_tx_acknowledge(const struct kvaser_usb *dev,
>  	spin_lock_irqsave(&priv->tx_contexts_lock, flags);
>  
>  	can_get_echo_skb(priv->netdev, context->echo_index);
> -	context->echo_index = MAX_TX_URBS;
> +	context->echo_index = dev->max_tx_urbs;
>  	--priv->active_tx_contexts;
>  	netif_wake_queue(priv->netdev);
>  
> @@ -1512,11 +1520,13 @@ error:
>  
>  static void kvaser_usb_reset_tx_urb_contexts(struct kvaser_usb_net_priv *priv)
>  {
> -	int i;
> +	int i, max_tx_urbs;
> +
> +	max_tx_urbs = priv->dev->max_tx_urbs;
>  
>  	priv->active_tx_contexts = 0;
> -	for (i = 0; i < MAX_TX_URBS; i++)
> -		priv->tx_contexts[i].echo_index = MAX_TX_URBS;
> +	for (i = 0; i < max_tx_urbs; i++)
> +		priv->tx_contexts[i].echo_index = max_tx_urbs;
>  }
>  
>  /* This method might sleep. Do not call it in the atomic context
> @@ -1702,14 +1712,14 @@ static netdev_tx_t kvaser_usb_start_xmit(struct sk_buff *skb,
>  		*msg_tx_can_flags |= MSG_FLAG_REMOTE_FRAME;
>  
>  	spin_lock_irqsave(&priv->tx_contexts_lock, flags);
> -	for (i = 0; i < ARRAY_SIZE(priv->tx_contexts); i++) {
> -		if (priv->tx_contexts[i].echo_index == MAX_TX_URBS) {
> +	for (i = 0; i < dev->max_tx_urbs; i++) {
> +		if (priv->tx_contexts[i].echo_index == dev->max_tx_urbs) {
>  			context = &priv->tx_contexts[i];
>  
>  			context->echo_index = i;
>  			can_put_echo_skb(skb, netdev, context->echo_index);
>  			++priv->active_tx_contexts;
> -			if (priv->active_tx_contexts >= MAX_TX_URBS)
> +			if (priv->active_tx_contexts >= dev->max_tx_urbs)
>  				netif_stop_queue(netdev);
>  
>  			break;
> @@ -1743,7 +1753,7 @@ static netdev_tx_t kvaser_usb_start_xmit(struct sk_buff *skb,
>  		spin_lock_irqsave(&priv->tx_contexts_lock, flags);
>  
>  		can_free_echo_skb(netdev, context->echo_index);
> -		context->echo_index = MAX_TX_URBS;
> +		context->echo_index = dev->max_tx_urbs;
>  		--priv->active_tx_contexts;
>  		netif_wake_queue(netdev);
>  
> @@ -1881,7 +1891,7 @@ static int kvaser_usb_init_one(struct usb_interface *intf,
>  	if (err)
>  		return err;
>  
> -	netdev = alloc_candev(sizeof(*priv), MAX_TX_URBS);
> +	netdev = alloc_candev(sizeof(*priv), dev->max_tx_urbs);
>  	if (!netdev) {
>  		dev_err(&intf->dev, "Cannot alloc candev\n");
>  		return -ENOMEM;
> @@ -1889,6 +1899,13 @@ static int kvaser_usb_init_one(struct usb_interface *intf,
>  
>  	priv = netdev_priv(netdev);
>  
> +	priv->tx_contexts = kzalloc(dev->max_tx_urbs *
> +				    sizeof(*priv->tx_contexts), GFP_KERNEL);
> +	if (!priv->tx_contexts) {
> +		free_candev(netdev);
> +		return -ENOMEM;
> +	}

I'm missing a free for the priv->tx_contexts. I see two options:

1) use devm_kzalloc(), or
2) move struct kvaser_usb_tx_urb_context tx_contexts[]; to the end of
   struct kvaser_usb_net_priv, see [1] for an example.

   Without further testing, I think the correct alloc for that case
   would be:
       alloc_candev(sizeof(*priv + dev->max_tx_urbs *
               sizeof(struct kvaser_usb_tx_urb_context))

Marc

[1] http://stackoverflow.com/questions/2060974/dynamic-array-in-struct-c

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