[PATCH net v3 1/2] net: airoha: handle RX_NO_CPU_DSCP interrupt, not just RX_DONE

[Vitaliy Sochnev]

> Since you're not sure you should probably add a timer to retry
> later? Maybe the IRQ is not needed at all, you could just check 
> on allocation failure if the right is completely drained or have 
> a periodic task a'la fbnic_napi_depletion_check()

No timer either: the depletion path is not the one being hit. Please drop
this patch.

Instrumented builds logged zero NO_CPU_DSCP events across every run, with
REG_INT_ENABLE(bank0, 1) reading 0x839F839F, so the bit was unmasked for
ring 4. page_pool_dev_alloc_frag() never failed and q->queued never
reached zero, so the ring never enters the state this patch handles.
Images with and without it stalled identically.

The stall was RX rings smaller than 32 descriptors, fixed by 2/2 of this
series, e84b89f17a12 ("net: airoha: grow the small RX rings"). Details in
my report on the cover thread.

airoha_irq_handler() does discard the NO_CPU_DSCP bits, so handling them
may still be right, but I have no measurement showing it matters and will
not claim one.