[EXT] Re: [PATCH v2 3/3] event/cnxk: use WFE in Tx fc wait
Pavan Nikhilesh Bhagavatula
pbhagavatula at marvell.com
Fri Jun 16 08:46:00 CEST 2023
=
> On Tue, 13 Jun 2023 14:55:48 +0530
> <pbhagavatula at marvell.com> wrote:
>
> > static __rte_always_inline void
> > cn10k_sso_txq_fc_wait(const struct cn10k_eth_txq *txq)
> > {
> > +#ifdef RTE_ARCH_ARM64
> > + uint64_t space;
> > +
> > + asm volatile(PLT_CPU_FEATURE_PREAMBLE
> > + " ldxr %[space], [%[addr]] \n"
> > + " cmp %[adj], %[space] \n"
> > + " b.hi .Ldne%= \n"
> > + " sevl \n"
> > + ".Lrty%=: wfe \n"
> > + " ldxr %[space], [%[addr]] \n"
> > + " cmp %[adj], %[space] \n"
> > + " b.ls .Lrty%= \n"
> > + ".Ldne%=: \n"
> > + : [space] "=&r"(space)
> > + : [adj] "r"(txq->nb_sqb_bufs_adj), [addr] "r"(txq-
> >fc_mem)
> > + : "memory");
> > +#else
> > while ((uint64_t)txq->nb_sqb_bufs_adj <=
> > __atomic_load_n(txq->fc_mem, __ATOMIC_RELAXED))
> > ;
> > +#endif
> > }
>
> Rather than introduce assembly here, please extend existing rte_pause
> functions and then other drivers could benefit and it would fit
> existing WFE usage.
>
Yes, a future patch is planned to replace this and other occurrences with
RTE_WAIT_UNTIL_MASKED
> Something like:
>
> static __rte_always_inline void
> rte_wait_until_le_32(volatile uint32_t *addr, uint32_t expected,
> int memorder);
>
> Direct assembly in drivers is hard to maintain and should be forbidden.
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