topic Re: i.MXRT1176 ENET_QOS strange ISR triggering behaviour in i.MX RT Crossover MCUs

i.MXRT1176 ENET_QOS strange ISR triggering behaviour

Andre_M — Mon, 29 Apr 2024 19:09:44 GMT

I'm working with ENET_QOS on a custom board, following the 'evkmimxrt1170_lwip_ping_enet_qos_freertos_cm7' example.

The strange behaviour is this: sometimes, when I simply remove the ethernet cable, the processor keeps triggering the ENET_QOS_IRQHandler non-stop (with DMA_INTERRUPT_STATUS == 0) until the watchdog reboots the uC.

Since DMA_INTERRUPT_STATUS register value is 0, the function ENET_QOS_CommonIRQHandler (assigned as the ISR handler on s_enetqosIsr) just goes straight through, without going into any of the 'if' statements.

This is the state of the registers when the ISR triggers:

DMA_INTERRUPT_STATUS 0x0

MAC_INTERRUPT_ENABLE 0x0
MAC_INTERRUPT_STATUS 0x21
MTL_INTERRUPT_STATUS 0x0
DMA_CH0_INTERRUPT_ENABLE 0x8041
DMA_CH0_STATUS 0x404

I tried clearing the DMA_CH0_STATUS register inside the ISR, but it remained 0 afterwards and ISRs kept triggering:

// Clear STATUS for channel 0 base->DMA_CH[0].DMA_CHX_STAT |= base->DMA_CH[0].DMA_CHX_STAT;

Then I tried clearing the bits on MAC_INTERRUPT_STATUS. It seems that clearing bit 5 (LPIIS) solves the ISR spam:

volatile uint32_t discard; // read MAC_LPI_CONTROL_STATUS to clear MAC_INTERRUPT_STATUS bit 5 (0x20) discard = base->MAC_LPI_CONTROL_STATUS; (void)discard;

But it doesn't make sense, as this interrupt is not even enabled in MAC_INTERRUPT_ENABLE. What could explain this behaviour?

Re: i.MXRT1176 ENET_QOS strange ISR triggering behaviour

Kan_Li — Sat, 11 May 2024 06:33:29 GMT

Hi @Andre_M ,

Would you please tell me in which case removing the ethernet cable would 100% reproduce this issue? I will try to reproduce it here.

Best Regards,

Kan

Re: i.MXRT1176 ENET_QOS strange ISR triggering behaviour

mttjcksn — Wed, 24 Jul 2024 20:01:47 GMT

I have the exact same issue using this board: https://www.tq-group.com/en/products/tq-embedded/arm-architecture/mba117xl/
running a basic application reusing much of the qos multi-ring example.

I am not using Energy Efficient Ethernet.

I can also resolve the issue by clearing the LPI Interrupt Status bit.

Re: i.MXRT1176 ENET_QOS strange ISR triggering behaviour

jeffG1 — Fri, 22 Nov 2024 09:58:37 GMT

Hello.
I have a similar issue using a rt1176AVM8A. I have no interruption enabled :

MAC_INTERRUPT_ENABLE 00000000 : No interrupt mac interrupt enabled
DMA_CH0_INTERRUPT_ENABLE : 0x8000 : NIE

But I'm anyway spammed by interruption and the only way to get rid on it, is to clear the LPI Interrupt Status:

MAC_INTERRUPT_STATUS 00000021 : LPI Interrupt Status + RGMII Interrupt Status
MAC_LPI_CONTROL_STATUS 0000020C : RLPIST + RLPIEX + RLPIEN
DMA_INTERRUPT_STATUS 00000000
DMA_CH0_STATUS 00000445 :ET + RI + TBU + TI

In my case, I don't need to remove the cable, it happens right after the end of the autonegociation procedure.

Like the others, disabling Energy Efficient Ethernet seems to fix my problem, but can you ensure me that an another disabled interruption won't trig the ENET_QOS_IRQHandler ?

Regards