On AM65x silicon revision 1.0, 2.0, and 2.1, programming the MUXCNTL_n registers to configure input-output mapping of interrupt signals may result in a short glitch on the intended output signal, causing a spurious interrupt. Additionally, reprogramming the register to the same value may also cause a glitch.

The Interrupt Routers section in the device TRM also describes this behavior, which is applicable to multiple Interrupt Routers (INTRTR) instantiated in the device, including:

• WKUP_GPIOMUX_INTRTR0
• GPIO_INTRTR0
• MAIN2MCU_LVL_INTRTR0
• MAIN2MCU_PLS_INTRTR0
• TIMESYNC_INTRTR0
• CMPEVT_INTRTR0

To prevent system from servicing these spurious interrupts unintentionally, following programming sequence are recommended when configuring INTR interrupt mapping.

In systems where interrupt mapping is static, typically with RTOS or bare-metal programming, the following interrupt configuration sequence shall be followed:

1. Disable interrupt at GIC and VIM for the interrupt sourced from the INTRTR output;
2. Re-configure MUXCNTL_n on the specific INTRTR;
3. Clear spurious interrupt if any by clearing raw status;
4. Enable the interrupt at GIC and/or VIM.

In systems where static interrupt configurations not possible, such as Linux systems with standard GIC drivers, interrupt drivers must detect false interrupt caused by the glitch, and clear the false interrupt. This method can be performed by the following programming sequence:

• If possible to customize interrupt handler, the handler shall first clear any interrupts before the handler being initialized, otherwise,
• The handler must check the interrupt source (such as GPIO status) to check valid event exists, then service the interrupt.

In systems with shared IRQs where multiple INTRTRs map to the same GIC IRQ, the following pseudo code may be used for the global interrupt handler:

isr(irq)
{     if (!read_status_reg())        return IRQ_NONE; }

In this case, each ISR can check and report to global IRQ handler that it wasn't the cause of IRQ, allowing the global IRQ handler to call the next handler in the list for that IRQ. In case of spurious IRQ, all the handlers (if there are no events) will return IRQ_NONE, which means Linux kernel will report a spurious IRQ on that line as the global handler will report EOI.