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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: Philipp Rosenberger <p.rosenberger@kunbus.com>
Signed-off-by: Zhi Han <hanzhi09@gmail.com>
[lukas: rewrite commit message, linewrap request_threaded_irq() call]
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Reviewed-by: Piotr Raczynski <piotr.raczynski@intel.com>
Link: https://lore.kernel.org/r/342380d989ce26bc49f0e5d45fbb0416a5f7809f.1683606193.git.lukas@wunner.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Philipp Rosenberger 2023-05-09 06:28:56 +02:00 committed by Jakub Kicinski
parent bc88ba0cad
commit 995585ecdf
1 changed files with 6 additions and 22 deletions
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28
drivers/net/ethernet/microchip/enc28j60.c
View File

@ -58,7 +58,6 @@ struct enc28j60_net {
struct mutex lock; struct mutex lock;
struct sk_buff *tx_skb; struct sk_buff *tx_skb;
struct work_struct tx_work; struct work_struct tx_work;
struct work_struct irq_work;
struct work_struct setrx_work; struct work_struct setrx_work;
struct work_struct restart_work; struct work_struct restart_work;
u8 bank; /* current register bank selected */ u8 bank; /* current register bank selected */
@ -1118,10 +1117,9 @@ static int enc28j60_rx_interrupt(struct net_device *ndev)
return ret; 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 = struct enc28j60_net *priv = dev_id;
container_of(work, struct enc28j60_net, irq_work);
struct net_device *ndev = priv->netdev; struct net_device *ndev = priv->netdev;
int intflags, loop; int intflags, loop;
@ -1225,6 +1223,8 @@ static void enc28j60_irq_work_handler(struct work_struct *work)
/* re-enable interrupts */ /* re-enable interrupts */
locked_reg_bfset(priv, EIE, EIE_INTIE); 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); 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) static void enc28j60_tx_timeout(struct net_device *ndev, unsigned int txqueue)
{ {
struct enc28j60_net *priv = netdev_priv(ndev); struct enc28j60_net *priv = netdev_priv(ndev);
@ -1559,7 +1543,6 @@ static int enc28j60_probe(struct spi_device *spi)
mutex_init(&priv->lock); mutex_init(&priv->lock);
INIT_WORK(&priv->tx_work, enc28j60_tx_work_handler); INIT_WORK(&priv->tx_work, enc28j60_tx_work_handler);
INIT_WORK(&priv->setrx_work, enc28j60_setrx_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); INIT_WORK(&priv->restart_work, enc28j60_restart_work_handler);
spi_set_drvdata(spi, priv); /* spi to priv reference */ spi_set_drvdata(spi, priv); /* spi to priv reference */
SET_NETDEV_DEV(dev, &spi->dev); 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; /* Board setup must set the relevant edge trigger type;
* level triggers won't currently work. * 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 (ret < 0) {
if (netif_msg_probe(priv)) if (netif_msg_probe(priv))
dev_err(&spi->dev, "request irq %d failed (ret = %d)\n", dev_err(&spi->dev, "request irq %d failed (ret = %d)\n",