What causes "DMA: user settings error on DMA@{:08x} channel {}" in embassy-rs/embassy?

Ensure the DMA channel's security/privilege attributes match the executing context

DMA: user settings error on DMA@

Error message

DMA: user settings error on DMA@{:08x} channel {}

What it means

The GPDMA channel IRQ handler found the user settings error flag (USEF) set: the channel's programmed user settings (e.g. secure/privileged attribute or other policy bits) conflict with the actual access performed. The driver panics because the configured settings are invalid for the transaction.

Solutions

Ensure the DMA channel's security/privilege attributes match the executing context
Initialize channels from the same security world that runs the transfer
Reset/claim the channel before configuring and check no prior settings linger
Consult the reference manual's GPDMA security/privilege chapter for your chip

Defensive patterns

Strategy: validation

Validate before calling

// Before starting transfers, ensure the channel is configured in the same security world:
// read GPDMA SEC/PRIV channel attributes and compare with current execution mode (NS/CPUID checks).

Prevention

Configure and run DMA channels from the same TrustZone world that owns them
Avoid reusing channels left configured by the bootloader
Reset the channel before reconfiguring
Review the chip's GPDMA security/privilege documentation

When it happens

Trigger: Transfer configured with settings not permitted in the current security/privilege context (e.g. secure channel access from non-secure code, or TrustZone policy mismatch); channel settings registers modified inconsistently.

Common situations: Mixed secure/non-secure (TrustZone) STM32 configurations where the DMA channel is owned by the other world; enabling GPDMA channels with security attributes set by bootloader code.

Related errors

AI-assisted analysis of embassy-rs/embassy@463a07b963 (2026-09-10). Data as JSON: /api/errors/0db3713623c01a95. Report an issue: GitHub.

Appendix: source

Thrown at embassy-stm32/src/dma/gpdma/mod.rs:569

    {
        use embassy_hal_internal::interrupt::InterruptExt as _;
        info.irq.enable();
    }

    let state = &STATE[channel as usize];

    let ch = info.dma.ch(info.num);
    let sr = ch.sr().read();

    if sr.dtef() {
        panic!(
            "DMA: data transfer error on DMA@{:08x} channel {}",
            info.dma.cast().as_ptr() as u32,
            info.num
        );
    }
    if sr.usef() {
        panic!(
            "DMA: user settings error on DMA@{:08x} channel {}",
            info.dma.cast().as_ptr() as u32,
            info.num
        );
    }
    if sr.ulef() {
        panic!(
            "DMA: link transfer error on DMA@{:08x} channel {}",
            info.dma.cast().as_ptr() as u32,
            info.num
        );
    }

    if sr.htf() {
        ch.fcr().write(|w| w.set_htf(true));
    }

    if sr.tcf() {

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