Hi Jerin,
> > > > > > >
> > > > > > > i40e_asq_send_command: rd32 & wr32 under ThunderX gives
> > > > > > > unpredictable
> > > > > > > results. To solve this include rte memory
> > > > > > > barriers
> > > > > > >
> > > > > > > Signed-off-by: Satha Rao <skoteshwar at caviumnetworks.com>
> > > > > > > ---
> > > > > > > drivers/net/i40e/base/i40e_osdep.h | 14 ++++++++++++++
> > > > > > > 1 file changed, 14 insertions(+)
> > > > > > >
> > > > > > > diff --git a/drivers/net/i40e/base/i40e_osdep.h
> > > > > > > b/drivers/net/i40e/base/i40e_osdep.h
> > > > > > > index 38e7ba5..ffa3160 100644
> > > > > > > --- a/drivers/net/i40e/base/i40e_osdep.h
> > > > > > > +++ b/drivers/net/i40e/base/i40e_osdep.h
> > > > > > > @@ -158,7 +158,13 @@ do {
> > > > > > > \
> > > > > > > ((volatile uint32_t *)((char *)(a)->hw_addr + (reg)))
> > > > > > > static inline uint32_t i40e_read_addr(volatile void *addr)
> > > > > > > {
> > > > > > > +#if defined(RTE_ARCH_ARM64)
> > > > > > > + uint32_t val = rte_le_to_cpu_32(I40E_PCI_REG(addr));
> > > > > > > + rte_rmb();
> > > > > > > + return val;
> > > > > >
> > > > > > If you really need an rmb/wmb with MMIO read/writes on ARM,
> > > > > > I think you can avoid #ifdefs here and use rte_smp_rmb/rte_smp_wmb.
> > > > > > BTW, I suppose if you need it for i40e, you would need it for other
> > > > > > devices too.
> > > > >
> > > > > Yes. ARM would need for all devices(typically, the devices on
> > > > > external PCI bus).
> > > > > I guess rte_smp_rmb may not be the correct abstraction. So we need
> > > > > more of
> > > > > rte_rmb() as we need only non smp variant on IO side. I guess then it
> > > > > make sense to
> > > > > create new abstraction in eal with following variants so that each
> > > > > arch
> > > > > gets opportunity to make what it makes sense that specific platform
> > > > >
> > > > > rte_readb_relaxed
> > > > > rte_readw_relaxed
> > > > > rte_readl_relaxed
> > > > > rte_readq_relaxed
> > > > > rte_writeb_relaxed
> > > > > rte_writew_relaxed
> > > > > rte_writel_relaxed
> > > > > rte_writeq_relaxed
> > > > > rte_readb
> > > > > rte_readw
> > > > > rte_readl
> > > > > rte_readq
> > > > > rte_writeb
> > > > > rte_writew
> > > > > rte_writel
> > > > > rte_writeq
> > > > >
> > > > > Thoughts ?
> > > > >
> > > >
> > > > That seems like a lot of API calls!
> > > > Perhaps you can clarify - why would the rte_smp_rmb() not work for you?
> > >
> > > Currently arm64 mapped DMB as rte_smp_rmb() for smp case.
> > >
> > > Ideally for io barrier and non smp case, we need to map it as DSB and it
> > > is
> > > bit heavier than DMB
> >
> > Ok, so you need some new macro, like rte_io_(r|w)mb or so, that would
> > expand into dmb
> > for ARM, correct?
>
> The io barrier expands to dsb.
> http://lxr.free-electrons.com/source/arch/arm64/include/asm/io.h#L110
Sorry, yes I meant DSB here.
>
> >
> > >
> > > The linux kernel arm64 mappings
> > > http://lxr.free-electrons.com/source/arch/arm64/include/asm/io.h#L142
> > >
> > > DMB vs DSB
> > > https://community.arm.com/thread/3833
> > >
> > > The relaxed one are without any barriers.(the use case like accessing on
> > > chip peripherals may need only relaxed versions)
> > >
> > > Thoughts on new rte EAL abstraction?
> >
> > Looks like a lot of macros but if you guys think that would help - NP with
> > that :)
>
> I don't have strong opinion here. If there is concern on a lot of macros
> then, I can introduce only "rte_io_(r|w)mb" instead of
> read[b|w|l|q]/write[b|w|l|q]/relaxed.
> let me know?
I think we can have both.
The question is in the amount of work need to be done.
>
> > Again, in that case we probably can get rid of driver specific pci reg
> > read/write defines.
> Yes. But, That's going to have a lot of change :-(
Yes I agree, the changes would be quite significant.
>
> If there is no objection then I will introduce
> "read[b|w|l|q]/write[b|w|l|q]/relaxed" and then change all external pcie
> drivers
> with new macros.
That seems like a good idea to me.
Though as you said that seems quite a significant change.
Probably make sense to do it in 2 stages (just a suggestion):
First introduce rte_io_(r|w)mb and fix with it existing issues in the
particular drivers.
Second replace existing PMD specific xxx_read/write_addr() with your new
generic
Konstantin
