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can: janz-ican3: fix support for CAN_RAW_RECV_OWN_MSGS
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The Janz VMOD-ICAN3 firmware does not support any sort of TX-done
notification or interrupt. The driver previously used the hardware
loopback to attempt to work around this deficiency, but this caused all
sockets to receive all messages, even if CAN_RAW_RECV_OWN_MSGS is off.

Using the new function ican3_cmp_echo_skb(), we can drop the loopback
messages and return the original skbs. This fixes the issues with
CAN_RAW_RECV_OWN_MSGS.

A private skb queue is used to store the echo skbs. This avoids the need
for any index management.

Due to a lack of TX-error interrupts, bus errors are permanently
enabled, and are used as a TX-error notification. This is used to drop
an echo skb when transmission fails. Bus error packets are not generated
if the user has not enabled bus error reporting.

Signed-off-by: Ira W. Snyder <iws@ovro.caltech.edu>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
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Ira W. Snyder authored and Marc Kleine-Budde committed Jul 20, 2012
1 parent 88b5870 commit 83702f6
Showing 1 changed file with 157 additions and 46 deletions.
203 changes: 157 additions & 46 deletions drivers/net/can/janz-ican3.c
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Original file line number Diff line number Diff line change
Expand Up @@ -220,6 +220,9 @@ struct ican3_dev {
/* old and new style host interface */
unsigned int iftype;

/* queue for echo packets */
struct sk_buff_head echoq;

/*
* Any function which changes the current DPM page must hold this
* lock while it is performing data accesses. This ensures that the
Expand Down Expand Up @@ -925,7 +928,7 @@ static int ican3_handle_cevtind(struct ican3_dev *mod, struct ican3_msg *msg)
struct net_device *dev = mod->ndev;
struct net_device_stats *stats = &dev->stats;
enum can_state state = mod->can.state;
u8 status, isrc, rxerr, txerr;
u8 isrc, ecc, status, rxerr, txerr;
struct can_frame *cf;
struct sk_buff *skb;

Expand All @@ -941,15 +944,43 @@ static int ican3_handle_cevtind(struct ican3_dev *mod, struct ican3_msg *msg)
return -EINVAL;
}

skb = alloc_can_err_skb(dev, &cf);
if (skb == NULL)
return -ENOMEM;

isrc = msg->data[0];
ecc = msg->data[2];
status = msg->data[3];
rxerr = msg->data[4];
txerr = msg->data[5];

/*
* This hardware lacks any support other than bus error messages to
* determine if packet transmission has failed.
*
* When TX errors happen, one echo skb needs to be dropped from the
* front of the queue.
*
* A small bit of code is duplicated here and below, to avoid error
* skb allocation when it will just be freed immediately.
*/
if (isrc == CEVTIND_BEI) {
int ret;
dev_dbg(mod->dev, "bus error interrupt\n");

/* TX error */
if (!(ecc & ECC_DIR)) {
kfree_skb(skb_dequeue(&mod->echoq));
stats->tx_errors++;
} else {
stats->rx_errors++;
}

/* bus error reporting is off, return immediately */
if (!(mod->can.ctrlmode & CAN_CTRLMODE_BERR_REPORTING))
return 0;
}

skb = alloc_can_err_skb(dev, &cf);
if (skb == NULL)
return -ENOMEM;

/* data overrun interrupt */
if (isrc == CEVTIND_DOI || isrc == CEVTIND_LOST) {
dev_dbg(mod->dev, "data overrun interrupt\n");
Expand Down Expand Up @@ -978,9 +1009,6 @@ static int ican3_handle_cevtind(struct ican3_dev *mod, struct ican3_msg *msg)

/* bus error interrupt */
if (isrc == CEVTIND_BEI) {
u8 ecc = msg->data[2];

dev_dbg(mod->dev, "bus error interrupt\n");
mod->can.can_stats.bus_error++;
cf->can_id |= CAN_ERR_PROT | CAN_ERR_BUSERROR;

Expand All @@ -1000,12 +1028,8 @@ static int ican3_handle_cevtind(struct ican3_dev *mod, struct ican3_msg *msg)
break;
}

if (!(ecc & ECC_DIR)) {
if (!(ecc & ECC_DIR))
cf->data[2] |= CAN_ERR_PROT_TX;
stats->tx_errors++;
} else {
stats->rx_errors++;
}

cf->data[6] = txerr;
cf->data[7] = rxerr;
Expand Down Expand Up @@ -1089,6 +1113,88 @@ static void ican3_handle_message(struct ican3_dev *mod, struct ican3_msg *msg)
}
}

/*
* The ican3 needs to store all echo skbs, and therefore cannot
* use the generic infrastructure for this.
*/
static void ican3_put_echo_skb(struct ican3_dev *mod, struct sk_buff *skb)
{
struct sock *srcsk = skb->sk;

if (atomic_read(&skb->users) != 1) {
struct sk_buff *old_skb = skb;

skb = skb_clone(old_skb, GFP_ATOMIC);
kfree_skb(old_skb);
if (!skb)
return;
} else {
skb_orphan(skb);
}

skb->sk = srcsk;

/* save this skb for tx interrupt echo handling */
skb_queue_tail(&mod->echoq, skb);
}

static unsigned int ican3_get_echo_skb(struct ican3_dev *mod)
{
struct sk_buff *skb = skb_dequeue(&mod->echoq);
struct can_frame *cf;
u8 dlc;

/* this should never trigger unless there is a driver bug */
if (!skb) {
netdev_err(mod->ndev, "BUG: echo skb not occupied\n");
return 0;
}

cf = (struct can_frame *)skb->data;
dlc = cf->can_dlc;

/* check flag whether this packet has to be looped back */
if (skb->pkt_type != PACKET_LOOPBACK) {
kfree_skb(skb);
return dlc;
}

skb->protocol = htons(ETH_P_CAN);
skb->pkt_type = PACKET_BROADCAST;
skb->ip_summed = CHECKSUM_UNNECESSARY;
skb->dev = mod->ndev;
netif_receive_skb(skb);
return dlc;
}

/*
* Compare an skb with an existing echo skb
*
* This function will be used on devices which have a hardware loopback.
* On these devices, this function can be used to compare a received skb
* with the saved echo skbs so that the hardware echo skb can be dropped.
*
* Returns true if the skb's are identical, false otherwise.
*/
static bool ican3_echo_skb_matches(struct ican3_dev *mod, struct sk_buff *skb)
{
struct can_frame *cf = (struct can_frame *)skb->data;
struct sk_buff *echo_skb = skb_peek(&mod->echoq);
struct can_frame *echo_cf;

if (!echo_skb)
return false;

echo_cf = (struct can_frame *)echo_skb->data;
if (cf->can_id != echo_cf->can_id)
return false;

if (cf->can_dlc != echo_cf->can_dlc)
return false;

return memcmp(cf->data, echo_cf->data, cf->can_dlc) == 0;
}

/*
* Check that there is room in the TX ring to transmit another skb
*
Expand All @@ -1099,6 +1205,10 @@ static bool ican3_txok(struct ican3_dev *mod)
struct ican3_fast_desc __iomem *desc;
u8 control;

/* check that we have echo queue space */
if (skb_queue_len(&mod->echoq) >= ICAN3_TX_BUFFERS)
return false;

/* copy the control bits of the descriptor */
ican3_set_page(mod, mod->fasttx_start + (mod->fasttx_num / 16));
desc = mod->dpm + ((mod->fasttx_num % 16) * sizeof(*desc));
Expand Down Expand Up @@ -1149,10 +1259,27 @@ static int ican3_recv_skb(struct ican3_dev *mod)
/* convert the ICAN3 frame into Linux CAN format */
ican3_to_can_frame(mod, &desc, cf);

/* receive the skb, update statistics */
netif_receive_skb(skb);
/*
* If this is an ECHO frame received from the hardware loopback
* feature, use the skb saved in the ECHO stack instead. This allows
* the Linux CAN core to support CAN_RAW_RECV_OWN_MSGS correctly.
*
* Since this is a confirmation of a successfully transmitted packet
* sent from this host, update the transmit statistics.
*
* Also, the netdevice queue needs to be allowed to send packets again.
*/
if (ican3_echo_skb_matches(mod, skb)) {
stats->tx_packets++;
stats->tx_bytes += ican3_get_echo_skb(mod);
kfree_skb(skb);
goto err_noalloc;
}

/* update statistics, receive the skb */
stats->rx_packets++;
stats->rx_bytes += cf->can_dlc;
netif_receive_skb(skb);

err_noalloc:
/* toggle the valid bit and return the descriptor to the ring */
Expand All @@ -1175,13 +1302,13 @@ static int ican3_recv_skb(struct ican3_dev *mod)
static int ican3_napi(struct napi_struct *napi, int budget)
{
struct ican3_dev *mod = container_of(napi, struct ican3_dev, napi);
struct ican3_msg msg;
unsigned long flags;
int received = 0;
int ret;

/* process all communication messages */
while (true) {
struct ican3_msg msg;
ret = ican3_recv_msg(mod, &msg);
if (ret)
break;
Expand Down Expand Up @@ -1353,7 +1480,6 @@ static int __devinit ican3_startup_module(struct ican3_dev *mod)
static int ican3_open(struct net_device *ndev)
{
struct ican3_dev *mod = netdev_priv(ndev);
u8 quota;
int ret;

/* open the CAN layer */
Expand All @@ -1363,19 +1489,6 @@ static int ican3_open(struct net_device *ndev)
return ret;
}

/* set the bus error generation state appropriately */
if (mod->can.ctrlmode & CAN_CTRLMODE_BERR_REPORTING)
quota = ICAN3_BUSERR_QUOTA_MAX;
else
quota = 0;

ret = ican3_set_buserror(mod, quota);
if (ret) {
dev_err(mod->dev, "unable to set bus-error\n");
close_candev(ndev);
return ret;
}

/* bring the bus online */
ret = ican3_set_bus_state(mod, true);
if (ret) {
Expand Down Expand Up @@ -1407,6 +1520,9 @@ static int ican3_stop(struct net_device *ndev)
return ret;
}

/* drop all outstanding echo skbs */
skb_queue_purge(&mod->echoq);

/* close the CAN layer */
close_candev(ndev);
return 0;
Expand All @@ -1415,7 +1531,6 @@ static int ican3_stop(struct net_device *ndev)
static int ican3_xmit(struct sk_buff *skb, struct net_device *ndev)
{
struct ican3_dev *mod = netdev_priv(ndev);
struct net_device_stats *stats = &ndev->stats;
struct can_frame *cf = (struct can_frame *)skb->data;
struct ican3_fast_desc desc;
void __iomem *desc_addr;
Expand All @@ -1428,8 +1543,7 @@ static int ican3_xmit(struct sk_buff *skb, struct net_device *ndev)

/* check that we can actually transmit */
if (!ican3_txok(mod)) {
dev_err(mod->dev, "no free descriptors, stopping queue\n");
netif_stop_queue(ndev);
dev_err(mod->dev, "BUG: no free descriptors\n");
spin_unlock_irqrestore(&mod->lock, flags);
return NETDEV_TX_BUSY;
}
Expand All @@ -1443,6 +1557,14 @@ static int ican3_xmit(struct sk_buff *skb, struct net_device *ndev)
/* convert the Linux CAN frame into ICAN3 format */
can_frame_to_ican3(mod, cf, &desc);

/*
* This hardware doesn't have TX-done notifications, so we'll try and
* emulate it the best we can using ECHO skbs. Add the skb to the ECHO
* stack. Upon packet reception, check if the ECHO skb and received
* skb match, and use that to wake the queue.
*/
ican3_put_echo_skb(mod, skb);

/*
* the programming manual says that you must set the IVALID bit, then
* interrupt, then set the valid bit. Quite weird, but it seems to be
Expand All @@ -1461,19 +1583,7 @@ static int ican3_xmit(struct sk_buff *skb, struct net_device *ndev)
mod->fasttx_num = (desc.control & DESC_WRAP) ? 0
: (mod->fasttx_num + 1);

/* update statistics */
stats->tx_packets++;
stats->tx_bytes += cf->can_dlc;
kfree_skb(skb);

/*
* This hardware doesn't have TX-done notifications, so we'll try and
* emulate it the best we can using ECHO skbs. Get the next TX
* descriptor, and see if we have room to send. If not, stop the queue.
* It will be woken when the ECHO skb for the current packet is recv'd.
*/

/* copy the control bits of the descriptor */
/* if there is no free descriptor space, stop the transmit queue */
if (!ican3_txok(mod))
netif_stop_queue(ndev);

Expand Down Expand Up @@ -1669,6 +1779,7 @@ static int __devinit ican3_probe(struct platform_device *pdev)
mod->dev = &pdev->dev;
mod->num = pdata->modno;
netif_napi_add(ndev, &mod->napi, ican3_napi, ICAN3_RX_BUFFERS);
skb_queue_head_init(&mod->echoq);
spin_lock_init(&mod->lock);
init_completion(&mod->termination_comp);
init_completion(&mod->buserror_comp);
Expand Down

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