Re: [PATCH v2] net: stmmac: enable MAC rx/tx after DMA start

Hi,

On 7/27/26 08:14, Abid Ali wrote:

When the MAC receiver is enabled before the DMA channels are started,
incoming frames fill the MTL FIFO with no DMA engine to drain it.
If the PHY/Switch is already up at this point, and there is inflow
of packets towards EMAC, the per-queue FIFO overflows within this window.

Once the FIFO is full, the MTL read controller goes idle and never
retries delivery even if the DMA comes alive later on.
This behaviour happens due to enabling the MAC RX path before
the DMA setup is ready, and any delay between these events increases
the chances of blocking the rx path permanently.

The EMAC should only accept packets after the DMAs are enabled.
Similarly, the teardown should ensure the MAC rx/tx is stopped before
DMA engine is stopped.

Signed-off-by: Abid Ali <redacted>

Ah great ! This matches the programming model for the few ref manuals I
have, e.g. cycloneV manual does state that the MAC must be enabled after the
DMA has been configured.

Reviewed-by: Maxime Chevallier <maxime.chevallier@bootlin.com>

Maxime