On 5/9/13 11:19 AM, David Hauweele wrote:
> The transceiver may fail under heavy traffic when a frame is transmitted
> while receiving another frame.
>
> This patch uses a mutex to separate the transmission and reception of
> frames along with a secondary working queue to avoid a deadlock while
> waiting for the transmission interrupt.
>
Have you observed this failure? I have put this kind of thing in before
(several times actually) but ultimately convinced myself each time that
it was not necessary. I'm happy to be shown wrong.
> Signed-off-by: David Hauweele <da...@hauweele.net>
> ---
> drivers/net/ieee802154/mrf24j40.c | 22 +++++++++++++++++++++-
> 1 file changed, 21 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/ieee802154/mrf24j40.c
> b/drivers/net/ieee802154/mrf24j40.c
> index ede3ce4..1e3ddf3 100644
> --- a/drivers/net/ieee802154/mrf24j40.c
> +++ b/drivers/net/ieee802154/mrf24j40.c
> @@ -82,8 +82,10 @@ struct mrf24j40 {
> struct ieee802154_dev *dev;
>
> struct mutex buffer_mutex; /* only used to protect buf */
> + struct mutex txrx_mutex; /* avoid transmission while receiving a frame
> */
> struct completion tx_complete;
> struct work_struct irqwork;
> + struct work_struct rxwork;
> u8 *buf; /* 3 bytes. Used for SPI single-register transfers. */
> };
>
> @@ -353,6 +355,8 @@ static int mrf24j40_tx(struct ieee802154_dev *dev, struct
> sk_buff *skb)
> /* Set TXNACKREQ if the ACK bit is set in the packet. */
> if (skb->data[0] & IEEE802154_FC_ACK_REQ)
> val |= 0x4;
> +
> + mutex_lock(&devrec->txrx_mutex);
> write_short_reg(devrec, REG_TXNCON, val);
>
> INIT_COMPLETION(devrec->tx_complete);
> @@ -361,6 +365,9 @@ static int mrf24j40_tx(struct ieee802154_dev *dev, struct
> sk_buff *skb)
> ret = wait_for_completion_interruptible_timeout(
> &devrec->tx_complete,
> 5 * HZ);
> +
> + mutex_unlock(&devrec->txrx_mutex);
> +
> if (ret == -ERESTARTSYS)
> goto err;
> if (ret == 0) {
> @@ -535,6 +542,8 @@ static int mrf24j40_handle_rx(struct mrf24j40 *devrec)
> int ret = 0;
> struct sk_buff *skb;
>
> + mutex_lock(&devrec->txrx_mutex);
> +
> /* Turn off reception of packets off the air. This prevents the
> * device from overwriting the buffer while we're reading it. */
> ret = read_short_reg(devrec, REG_BBREG1, &val);
> @@ -575,6 +584,8 @@ out:
> val &= ~0x4; /* Clear RXDECINV */
> write_short_reg(devrec, REG_BBREG1, val);
>
> + mutex_unlock(&devrec->txrx_mutex);
> +
> return ret;
> }
>
> @@ -616,12 +627,19 @@ static void mrf24j40_isrwork(struct work_struct *work)
>
> /* Check for Rx */
> if (intstat & 0x8)
> - mrf24j40_handle_rx(devrec);
> + schedule_work(&devrec->rxwork);
>
mrf24f40_isrwork() is already called from a workqueue.
> out:
> enable_irq(devrec->spi->irq);
> }
>
> +static void mrf24j40_rxwork(struct work_struct *work)
> +{
> + struct mrf24j40 *devrec = container_of(work, struct mrf24j40, rxwork);
> +
> + mrf24j40_handle_rx(devrec);
> +}
> +
> static int mrf24j40_probe(struct spi_device *spi)
> {
> int ret = -ENOMEM;
> @@ -648,8 +666,10 @@ static int mrf24j40_probe(struct spi_device *spi)
> spi->max_speed_hz = MAX_SPI_SPEED_HZ;
>
> mutex_init(&devrec->buffer_mutex);
> + mutex_init(&devrec->txrx_mutex);
> init_completion(&devrec->tx_complete);
> INIT_WORK(&devrec->irqwork, mrf24j40_isrwork);
> + INIT_WORK(&devrec->rxwork, mrf24j40_rxwork);
> devrec->spi = spi;
> spi_set_drvdata(spi, devrec);
>
>
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