Re: [PATCH v3 3/8] rtc: abx80x: properly handle shared IRQs

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] Returning IRQ_NONE without masking or clearing unhandled RTC interrupts can cause an interrupt storm on the shared IRQ line.
--

--- Patch [3]: [PATCH v3 3/8] rtc: abx80x: properly handle shared IRQs ---
commit e06155ed4aeb662277df57a2324e881c6d065e84
Author: Antoni Pokusinski <apokusinski01@gmail.com>

rtc: abx80x: properly handle shared IRQs

This commit modifies the abx80x interrupt handler to only claim the IRQ and
clear the status register if the alarm or watchdog flags are explicitly set.
It aims to prevent claiming interrupts from other devices sharing the same
IRQ line.

> diff --git a/drivers/rtc/rtc-abx80x.c b/drivers/rtc/rtc-abx80x.c
> --- a/drivers/rtc/rtc-abx80x.c
> +++ b/drivers/rtc/rtc-abx80x.c

[ ... ]

> @@ -266,27 +266,34 @@ static irqreturn_t abx80x_handle_irq(int irq, void *dev_id)

[ ... ]

> -	if (status & ABX8XX_STATUS_WDT)
> +	if (status & ABX8XX_STATUS_WDT) {
>  		dev_alert(&client->dev, "watchdog timeout interrupt.\n");
> +		handled = IRQ_HANDLED;
> +	}
>  
> -	i2c_smbus_write_byte_data(client, ABX8XX_REG_STATUS, 0);
> +	if (handled == IRQ_HANDLED)
> +		i2c_smbus_write_byte_data(client, ABX8XX_REG_STATUS,
> +					  status & ~(ABX8XX_STATUS_AF | ABX8XX_STATUS_WDT));
>  
> -	return IRQ_HANDLED;
> +	return handled;

[Severity: High]
If the RTC hardware asserts an interrupt for a reason other than AF or WDT
(for example, a timer or century interrupt left enabled by a bootloader),
will this cause an interrupt storm?

Because handled remains IRQ_NONE, the handler skips the i2c_smbus_write_byte_data()
call and returns IRQ_NONE without clearing the unhandled RTC status bits.

Since the unhandled RTC interrupt is never cleared, the IRQ line will remain
asserted. This causes the kernel to immediately re-enter the handler until
the spurious IRQ detector steps in and completely disables the shared IRQ line.

Could we check if the status register indicates the interrupt originated
from this RTC, clear those bits, and return IRQ_HANDLED?

>  }

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260731184831.44037-1-apokusinski01@gmail.com?part=3