Commit 995585ec authored by Philipp Rosenberger's avatar Philipp Rosenberger Committed by Jakub Kicinski
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net: enc28j60: Use threaded interrupt instead of workqueue 



The Microchip ENC28J60 SPI Ethernet driver schedules a work item from
the interrupt handler because accesses to the SPI bus may sleep.

On PREEMPT_RT (which forces interrupt handling into threads) this
old-fashioned approach unnecessarily increases latency because an
interrupt results in first waking the interrupt thread, then scheduling
the work item.  So, a double indirection to handle an interrupt.

Avoid by converting the driver to modern threaded interrupt handling.

Signed-off-by: default avatarPhilipp Rosenberger <p.rosenberger@kunbus.com>
Signed-off-by: default avatarZhi Han <hanzhi09@gmail.com>
[lukas: rewrite commit message, linewrap request_threaded_irq() call]
Signed-off-by: default avatarLukas Wunner <lukas@wunner.de>
Reviewed-by: default avatarPiotr Raczynski <piotr.raczynski@intel.com>
Link: https://lore.kernel.org/r/342380d989ce26bc49f0e5d45fbb0416a5f7809f.1683606193.git.lukas@wunner.de


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent bc88ba0c

drivers/net/ethernet/microchip/enc28j60.c

+6 −22
Original line number Diff line number Diff line
@@ -58,7 +58,6 @@ struct enc28j60_net { 
	struct mutex lock;

	struct sk_buff *tx_skb;

	struct work_struct tx_work;

	struct work_struct irq_work;

	struct work_struct setrx_work;

	struct work_struct restart_work;

	u8 bank;		/* current register bank selected */
@@ -1118,10 +1117,9 @@ static int enc28j60_rx_interrupt(struct net_device *ndev) 
	return ret;

}



static void enc28j60_irq_work_handler(struct work_struct *work)

static irqreturn_t enc28j60_irq(int irq, void *dev_id)

{

	struct enc28j60_net *priv =

		container_of(work, struct enc28j60_net, irq_work);

	struct enc28j60_net *priv = dev_id;

	struct net_device *ndev = priv->netdev;

	int intflags, loop;
@@ -1225,6 +1223,8 @@ static void enc28j60_irq_work_handler(struct work_struct *work) 


	/* re-enable interrupts */

	locked_reg_bfset(priv, EIE, EIE_INTIE);



	return IRQ_HANDLED;

}



/*
@@ -1309,22 +1309,6 @@ static void enc28j60_tx_work_handler(struct work_struct *work) 
	enc28j60_hw_tx(priv);

}



static irqreturn_t enc28j60_irq(int irq, void *dev_id)

{

	struct enc28j60_net *priv = dev_id;



	/*

	 * Can't do anything in interrupt context because we need to

	 * block (spi_sync() is blocking) so fire of the interrupt

	 * handling workqueue.

	 * Remember that we access enc28j60 registers through SPI bus

	 * via spi_sync() call.

	 */

	schedule_work(&priv->irq_work);



	return IRQ_HANDLED;

}



static void enc28j60_tx_timeout(struct net_device *ndev, unsigned int txqueue)

{

	struct enc28j60_net *priv = netdev_priv(ndev);
@@ -1559,7 +1543,6 @@ static int enc28j60_probe(struct spi_device *spi) 
	mutex_init(&priv->lock);

	INIT_WORK(&priv->tx_work, enc28j60_tx_work_handler);

	INIT_WORK(&priv->setrx_work, enc28j60_setrx_work_handler);

	INIT_WORK(&priv->irq_work, enc28j60_irq_work_handler);

	INIT_WORK(&priv->restart_work, enc28j60_restart_work_handler);

	spi_set_drvdata(spi, priv);	/* spi to priv reference */

	SET_NETDEV_DEV(dev, &spi->dev);
@@ -1578,7 +1561,8 @@ static int enc28j60_probe(struct spi_device *spi) 
	/* Board setup must set the relevant edge trigger type;

	 * level triggers won't currently work.

	 */

	ret = request_irq(spi->irq, enc28j60_irq, 0, DRV_NAME, priv);

	ret = request_threaded_irq(spi->irq, NULL, enc28j60_irq, IRQF_ONESHOT,

				   DRV_NAME, priv);

	if (ret < 0) {

		if (netif_msg_probe(priv))

			dev_err(&spi->dev, "request irq %d failed (ret = %d)\n",