Re: [dpdk-dev] [PATCH 23/28] net/ixgbe: use eal I/O device memory read/write API

[Santosh Shukla <santosh.shukla@caviumnetworks.com>]

Hi Jiangbo,

On Thu, Dec 15, 2016 at 08:40:19PM -0800, Santosh Shukla wrote:
> On Thu, Dec 15, 2016 at 04:37:12PM +0800, Jianbo Liu wrote:
> > On 14 December 2016 at 09:55, Jerin Jacob
> > <jerin.jacob@caviumnetworks.com> wrote:
> > > From: Santosh Shukla <santosh.shukla@caviumnetworks.com>
> > >
> > 
> > memory barrier operation is put inside IXGBE_PCI_REG_READ/WRITE in
> > your change, but I found rte_*mb is called before these macros in some
> > places.
> > Can you remove all these redundant calls? And please do the same
> > checking for other drivers.
> >
> 
> Ok.
> 
> Thinking of adding _relaxed_rd/wr style macro agnostic to arch for ixgbe case 
> in particular. Such that for those code incident:
> x86 case> first default barrier + relaxed call.
> arm case> first default barrier + relaxed call.
> 
> Does that make sense to you? If so then will take care in v2.
> 
> Santosh.

We spend time looking at drivers code where double barrier
may happen. Most of them are in driver init path,
configuration/control path code. So keeping double
barrier won't impact performance. 

We plan to replace only fast path code with _relaxed
style API's. That way we won't impact each driver
performance and we'll have the clean port. 

Does it make sense? Thought?

> 
> > >  #define IXGBE_PCI_REG_ADDR(hw, reg) \
> > >         ((volatile uint32_t *)((char *)(hw)->hw_addr + (reg)))
> > > --
> > > 2.5.5
> > >