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net: stmmac: dwxgmac2: configure INTM for per-channel interrupt routing

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The XGMAC DMA_MODE register has an INTM field (bits 13:12) that
controls interrupt routing behavior for DMA transfer completion
events:

  00 (default): sbd_perch_* are pulse signals, sbd_intr_o is also
                asserted for each completion event.
  01:          sbd_perch_* are level signals, sbd_intr_o is NOT
                asserted for packet transfer completion events.

When multi-MSI is enabled, per-channel TX/RX interrupts are expected
to arrive on their dedicated lines.  In the default INTM=00 mode,
sbd_intr_o also fires for DMA completion events, but the multi-MSI
handler stmmac_mac_interrupt() only processes MAC-layer events (LPI,
PMT, timestamps) and returns IRQ_NONE for every DMA completion
interrupt, resulting in a continuous stream of unhandled interrupts
on the common IRQ.

Hardware verification with XGMAC and multi-MSI enabled:

  INTM=00: 5.4 million common IRQ interrupts in 3 seconds, ~1.8
           million IRQ_NONE returns per second.
  INTM=01: 0 common IRQ interrupts, per-channel IRQs work normally,
           10G line rate works correctly.

Set INTM to mode 1 when multi-MSI is enabled.  This matches the
existing GMAC4 implementation.

XGMAC multi-MSI has never worked correctly since it was introduced.

Signed-off-by: Zxyan Zhu <zxyan0222@gmail.com>
Reviewed-by: Qingfang Deng <qingfang.deng@linux.dev>
Reviewed-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Link: https://patch.msgid.link/20260729023653.1162763-1-zxyan0222@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Zxyan Zhu 2026-07-29 10:36:53 +08:00 • committed by Jakub Kicinski
commit 4d3839943b
2 changed files with 12 additions and 0 deletions
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