Re: [net PATCH 13/13] fbnic: Disable PTP completions during the Tx force-flush

[netdev-bot+sashiko@kernel.org]

Thank you for your contribution! Sashiko AI review found more severe
issue(s) in other patches of this series. This mail is only an FYI, in case
you want to address the nit picks below when you respin.

Low priority / nit picks for your consideration:

- [Low] The Fixes: tag names the wrong commit.

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fbnic: Disable PTP completions during the Tx force-flush

When the Tx queues fail to go idle, fbnic_tx_flush() sets only
FBNIC_TMI_DROP_CTRL_EN. Timestamped frames are then dropped while their
PTP completions are still forwarded to the host. This patch also sets
FBNIC_TMI_DROP_CTRL_CMPL_DIS during the flush so those completions are
drained, and clears both bits in fbnic_tx_flush_off().

> Fixes: 40bf06a160a1 ("eth: fbnic: Implement Tx queue alloc/start/stop/free")

[Severity: Low]
Is this the right commit for the Fixes tag?

40bf06a160a1 added fbnic_tx_flush(), fbnic_tx_flush_off() and
fbnic_wait_all_queues_idle(). Its commit message says it has "No actual
datapath / packet handling here, yet". At that point the driver never
asked the hardware for Tx timestamp completions.

The symptom in the commit message comes from fbnic_clean_tsq() in
fbnic_txrx.c:

	if (head == ring->tail) {
		if (unlikely(net_ratelimit()))
			netdev_err(nv->napi.dev,
				   "Tx timestamp without matching packet\n");
		return;
	}

git blame shows that this code was added later by:

  ad3d9f8bc66c ("eth: fbnic: add TX packets timestamping support")

That commit also added the request for Tx timestamp completions.

So the leaked completion can't happen on a tree that has 40bf06a160a1 but
not ad3d9f8bc66c. ad3d9f8bc66c is not in v6.12, but v6.12.y already has
the flush code.

Stable tooling that relies on the current tag could pick this patch for
6.12.y, where the problem can't occur.

Should the tag name ad3d9f8bc66c instead, or include it as a second
Fixes tag?

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Sashiko AI review · https://netdev-ai.bots.linux.dev/sashiko/#/patchset/179322311834.40667.5383039334126572422.stgit%40ahduyck-xeon-server.home.arpa