Re: [PATCH net v3 1/2] net: ethernet: oa_tc6: Interrupt is active low, level triggered.

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] IRQ storm and starvation caused by level-triggered interrupt without IRQF_ONESHOT or manual masking.
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commit 3908a29ac2b1392995dbf0f4228af86bbddb0261
Author: Selvamani Rajagopal <Selvamani.Rajagopal@onsemi.com>

net: ethernet: oa_tc6: Interrupt is active low, level triggered.

According OPEN Alliance 10BASET1x MAC-PHY Serial Interface
specification, interrupt is active low, level triggered.

> diff --git a/drivers/net/ethernet/oa_tc6.c b/drivers/net/ethernet/oa_tc6.c
> index 91a906a7918a2..667faf1554053 100644
> --- a/drivers/net/ethernet/oa_tc6.c
> +++ b/drivers/net/ethernet/oa_tc6.c
> @@ -1323,7 +1323,7 @@ struct oa_tc6 *oa_tc6_init(struct spi_device *spi, struct net_device *netdev)
>  	sched_set_fifo(tc6->spi_thread);
>  
>  	ret = devm_request_irq(&tc6->spi->dev, tc6->spi->irq, oa_tc6_macphy_isr,
> -			       IRQF_TRIGGER_FALLING, dev_name(&tc6->spi->dev),
> +			       IRQF_TRIGGER_LOW, dev_name(&tc6->spi->dev),
>  			       tc6);

[Severity: High]
Does changing this to a level-triggered interrupt cause an IRQ storm?

Looking at the primary hardirq handler:

drivers/net/ethernet/oa_tc6.c:oa_tc6_macphy_isr() {
    ...
    tc6->int_flag = true;
    wake_up_interruptible(&tc6->spi_wq);
    return IRQ_HANDLED;
}

Since the handler returns IRQ_HANDLED without clearing the hardware condition
on the device, the IRQ core will immediately unmask the line. Because the
MAC-PHY is still holding the line low (waiting for the SPI kthread to run and
clear it), the interrupt will instantly re-trigger.

Could this starve the awakened spi_wq kthread and lead to a CPU lockup or the
kernel permanently disabling the interrupt line? Should this use a threaded
IRQ with IRQF_ONESHOT, or explicitly disable the IRQ in the handler until the
kthread completes the SPI transfer?

>  	if (ret) {
>  		dev_err(&tc6->spi->dev, "Failed to request macphy isr %d\n",

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Sashiko AI review · https://sashiko.dev/#/patchset/20260601-level-trigger-v3-0-da73e7010532@onsemi.com?part=1