Re: [PATCH v2] i2c: ls2x-v2: return IRQ_HANDLED after servicing an error

[Binbin Zhou <zhoubinbin@loongson.cn>]

Hi David:

Thanks for your patch.

On 2026/5/6 23:40, David Carlier wrote:
> The event ISR reads SR1 and, when an error flag (ARLO/AF/BERR) is set,
> calls loongson2_i2c_isr_error() which clears the offending flag, issues
> STOP for the AF case, records msg->result, masks every CR2 interrupt
> enable and completes the waiter. The handler then returns IRQ_NONE,
> declaring to the IRQ core that the device did not interrupt.
> 
> That report is wrong. The device did interrupt and the handler fully
> serviced it. Because the IRQ is requested with IRQF_SHARED, the genirq
> spurious-IRQ tracker counts each error as unhandled. A bus that emits
> sporadic NACKs, arbitration losses or bus errors will therefore march
> toward the spurious-IRQ threshold and the line can end up disabled,
> wedging the controller.
> 
> Return IRQ_HANDLED on this path. The other IRQ_NONE site, taken when
> neither an event nor an error bit is set, remains correct.
> 
> Fixes: 6d1b0785f6d5 ("i2c: ls2x-v2: Add driver for Loongson-2K0300 I2C controller")
> Assisted-by: Codex:GPT-5.5
> Signed-off-by: David Carlier <devnexen@gmail.com>

I tested the above boundary conditions on the Loongson-2K0300 platform, 
and the issue does indeed exist.

Reviewed-by: Binbin Zhou <zhoubinbin@loongson.cn>
Tested-by: Binbin Zhou <zhoubinbin@loongson.cn>
> ---
> v2:
>   - Add Assisted-by: Codex:GPT-5.5 trailer (no code change).
> 
>   drivers/i2c/busses/i2c-ls2x-v2.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/i2c/busses/i2c-ls2x-v2.c b/drivers/i2c/busses/i2c-ls2x-v2.c
> index 517760d70169..9df73557ecc4 100644
> --- a/drivers/i2c/busses/i2c-ls2x-v2.c
> +++ b/drivers/i2c/busses/i2c-ls2x-v2.c
> @@ -304,7 +304,7 @@ static irqreturn_t loongson2_i2c_isr_event(int irq, void *data)
>   	regmap_read(priv->regmap, LOONGSON2_I2C_SR1, &status);
>   	if (status & LOONGSON2_I2C_SR1_ITERREN_MASK) {
>   		loongson2_i2c_isr_error(status, data);
> -		return IRQ_NONE;
> +		return IRQ_HANDLED;
>   	}
>   
>   	regmap_read(priv->regmap, LOONGSON2_I2C_CR2, &cr2);

-- 
Thanks.
Binbin