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

[Binbin Zhou <zhoubinbin@loongson.cn>]

Hi all:

On 2026/5/6 17:11, Andy Shevchenko wrote:
> On Wed, May 06, 2026 at 05:48:18AM +0100, 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.
> Have you exhibited this on a real HW?
>
>> Return IRQ_HANDLED on this path. The other IRQ_NONE site, taken when
>> neither an event nor an error bit is set, remains correct.
> Hmm... This sounds logical, but we need the Loongson folks to confirm as this
> is sensitive code and changes like this may affect existing work flows.

I will try to test this boundary case in the next couple of days.

>
>>   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);
> P.S.
> Is the analysis and/or commit message AI assisted?
Thanks.
Binbin
>