[PATCH] i2c: aspeed: change debug level in irq handler

[Paul Menzel]

Dear Jian,


Thank you for the patch.

Am 18.06.25 um 12:21 schrieb Jian Zhang:
> In interrupt context, using dev_err() can potentially cause latency
> or affect system responsiveness due to printing to console.
> 
> In our scenario, under certain conditions, i2c1 repeatedly printed
> "irq handled != irq. expected ..." around 20 times within 1 second.

Any idea, why you hit this error at all?

> Each dev_err() log introduced approximately 10ms of blocking time,
> which delayed the handling of other interrupts — for example, i2c2.
> 
> At the time, i2c2 was performing a PMBus firmware upgrade. The
> target device on i2c2 was time-sensitive, and the upgrade protocol
> was non-retryable. As a result, the delay caused by frequent error
> logging led to a timeout and ultimately a failed firmware upgrade.
> 
> Frequent error printing in interrupt context can be dangerous,
> as it introduces latency and interferes with time-critical tasks.
> This patch changes the log level from dev_err() to dev_dbg() to
> reduce potential impact.

Thank you for the patch and the problem description. Hiding an error 
condition behind debug level is also not good, as administrators might 
miss hardware issues. I do not have a solution. Is there something 
similar to WARN_ONCE? Maybe the level should be a warning instead of 
error, because the system is often able to cope with this?

The code is from 2017, so should be well tested actually, shouldn’t it?

> Signed-off-by: Jian Zhang <zhangjian.3032 at bytedance.com>
> ---
>   drivers/i2c/busses/i2c-aspeed.c | 18 +++++++++---------
>   1 file changed, 9 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-aspeed.c b/drivers/i2c/busses/i2c-aspeed.c
> index 1550d3d552ae..38e23c826f39 100644
> --- a/drivers/i2c/busses/i2c-aspeed.c
> +++ b/drivers/i2c/busses/i2c-aspeed.c
> @@ -317,7 +317,7 @@ static u32 aspeed_i2c_slave_irq(struct aspeed_i2c_bus *bus, u32 irq_status)
>   	switch (bus->slave_state) {
>   	case ASPEED_I2C_SLAVE_READ_REQUESTED:
>   		if (unlikely(irq_status & ASPEED_I2CD_INTR_TX_ACK))
> -			dev_err(bus->dev, "Unexpected ACK on read request.\n");
> +			dev_dbg(bus->dev, "Unexpected ACK on read request.\n");
>   		bus->slave_state = ASPEED_I2C_SLAVE_READ_PROCESSED;
>   		i2c_slave_event(slave, I2C_SLAVE_READ_REQUESTED, &value);
>   		writel(value, bus->base + ASPEED_I2C_BYTE_BUF_REG);
> @@ -325,7 +325,7 @@ static u32 aspeed_i2c_slave_irq(struct aspeed_i2c_bus *bus, u32 irq_status)
>   		break;
>   	case ASPEED_I2C_SLAVE_READ_PROCESSED:
>   		if (unlikely(!(irq_status & ASPEED_I2CD_INTR_TX_ACK))) {
> -			dev_err(bus->dev,
> +			dev_dbg(bus->dev,
>   				"Expected ACK after processed read.\n");
>   			break;
>   		}
> @@ -354,7 +354,7 @@ static u32 aspeed_i2c_slave_irq(struct aspeed_i2c_bus *bus, u32 irq_status)
>   		/* Slave was just started. Waiting for the next event. */;
>   		break;
>   	default:
> -		dev_err(bus->dev, "unknown slave_state: %d\n",
> +		dev_dbg(bus->dev, "unknown slave_state: %d\n",
>   			bus->slave_state);
>   		bus->slave_state = ASPEED_I2C_SLAVE_INACTIVE;
>   		break;
> @@ -459,7 +459,7 @@ static u32 aspeed_i2c_master_irq(struct aspeed_i2c_bus *bus, u32 irq_status)
>   
>   	/* We are in an invalid state; reset bus to a known state. */
>   	if (!bus->msgs) {
> -		dev_err(bus->dev, "bus in unknown state. irq_status: 0x%x\n",
> +		dev_dbg(bus->dev, "bus in unknown state. irq_status: 0x%x\n",
>   			irq_status);
>   		bus->cmd_err = -EIO;
>   		if (bus->master_state != ASPEED_I2C_MASTER_STOP &&
> @@ -523,7 +523,7 @@ static u32 aspeed_i2c_master_irq(struct aspeed_i2c_bus *bus, u32 irq_status)
>   			irq_handled |= ASPEED_I2CD_INTR_TX_NAK;
>   			goto error_and_stop;
>   		} else if (unlikely(!(irq_status & ASPEED_I2CD_INTR_TX_ACK))) {
> -			dev_err(bus->dev, "slave failed to ACK TX\n");
> +			dev_dbg(bus->dev, "slave failed to ACK TX\n");
>   			goto error_and_stop;
>   		}
>   		irq_handled |= ASPEED_I2CD_INTR_TX_ACK;
> @@ -546,7 +546,7 @@ static u32 aspeed_i2c_master_irq(struct aspeed_i2c_bus *bus, u32 irq_status)
>   		fallthrough;
>   	case ASPEED_I2C_MASTER_RX:
>   		if (unlikely(!(irq_status & ASPEED_I2CD_INTR_RX_DONE))) {
> -			dev_err(bus->dev, "master failed to RX\n");
> +			dev_dbg(bus->dev, "master failed to RX\n");
>   			goto error_and_stop;
>   		}
>   		irq_handled |= ASPEED_I2CD_INTR_RX_DONE;
> @@ -577,7 +577,7 @@ static u32 aspeed_i2c_master_irq(struct aspeed_i2c_bus *bus, u32 irq_status)
>   		goto out_no_complete;
>   	case ASPEED_I2C_MASTER_STOP:
>   		if (unlikely(!(irq_status & ASPEED_I2CD_INTR_NORMAL_STOP))) {
> -			dev_err(bus->dev,
> +			dev_dbg(bus->dev,
>   				"master failed to STOP. irq_status:0x%x\n",
>   				irq_status);
>   			bus->cmd_err = -EIO;
> @@ -589,7 +589,7 @@ static u32 aspeed_i2c_master_irq(struct aspeed_i2c_bus *bus, u32 irq_status)
>   		bus->master_state = ASPEED_I2C_MASTER_INACTIVE;
>   		goto out_complete;
>   	case ASPEED_I2C_MASTER_INACTIVE:
> -		dev_err(bus->dev,
> +		dev_dbg(bus->dev,
>   			"master received interrupt 0x%08x, but is inactive\n",
>   			irq_status);
>   		bus->cmd_err = -EIO;
> @@ -665,7 +665,7 @@ static irqreturn_t aspeed_i2c_bus_irq(int irq, void *dev_id)
>   
>   	irq_remaining &= ~irq_handled;
>   	if (irq_remaining)
> -		dev_err(bus->dev,
> +		dev_dbg(bus->dev,
>   			"irq handled != irq. expected 0x%08x, but was 0x%08x\n",
>   			irq_received, irq_handled);
>   


Kind regards,

Paul