Re: [Intel-wired-lan] [iwl-net v1 1/2] igc: Fix missing time sync events

[Kurt Kanzenbach <kurt@linutronix.de>]

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On Fri Feb 16 2024, Vinicius Costa Gomes wrote:
> Fix "double" clearing of interrupts, which can cause external events
> or timestamps to be missed.
>
> The IGC_TSIRC Time Sync Interrupt Cause register can be cleared in two
> ways, by either reading it or by writing '1' into the specific cause
> bit. This is documented in section 8.16.1.
>
> The following flow was used:
>  1. read IGC_TSIRC into 'tsicr';
>  2. handle the interrupts present in 'tsirc' and mark them in 'ack';
>  3. write 'ack' into IGC_TSICR;
>
> As both (1) and (3) will clear the interrupt cause, if an interrupt
> happens between (1) and (3) it will be ignored, causing events to be
> missed.
>
> Remove the extra clear in (3).
>
> Fixes: 2c344ae24501 ("igc: Add support for TX timestamping")
> Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>

No obvious issues found while testing.

Reviewed-by: Kurt Kanzenbach <kurt@linutronix.de>
Tested-by: Kurt Kanzenbach <kurt@linutronix.de> # Intel i225

Thanks!

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