Re: [dpdk-dev] [PATCH v3] raw/ntb: add Icelake support for Intel NTB

["Li, Xiaoyun" <xiaoyun.li@intel.com>]

Hi

> -----Original Message-----
> From: Wu, Jingjing <jingjing.wu@intel.com>
> Sent: Tuesday, September 8, 2020 00:16
> To: Li, Xiaoyun <xiaoyun.li@intel.com>
> Cc: dev@dpdk.org; Maslekar, Omkar <omkar.maslekar@intel.com>
> Subject: RE: [PATCH v3] raw/ntb: add Icelake support for Intel NTB
> 
> > > > -	rte_write64(limit, limit_addr);
> > > > +	if (is_gen3_ntb(hw)) {
> > > > +		/* Setup the external point so that remote can access. */
> > > > +		xlat_off = XEON_EMBAR1_OFFSET + 8 * mw_idx;
> > > > +		xlat_addr = hw->hw_addr + xlat_off;
> > > > +		limit_off = XEON_EMBAR1XLMT_OFFSET +
> > > > +			    mw_idx * XEON_BAR_INTERVAL_OFFSET;
> > > > +		limit_addr = hw->hw_addr + limit_off;
> > > > +		base = rte_read64(xlat_addr);
> > > > +		base &= ~0xf;
> > > > +		limit = base + size;
> > > > +		rte_write64(limit, limit_addr);
> > > > +	} else if (is_gen4_ntb(hw)) {
> > > Can we use a variable in struct to indicate it's gen4 or gen3 after
> > > init instead of check it every time?
> >
> > What's the difference? It comes from the value in hw->pci_dev->id.device_id.
> > Checking it in this way is trying to make it easier to extend it for gen2 ntb in the
> future.
> > It's not either gen3 or gen4.
> > I don't think it makes sense to have a bool value to indicate it's gen3 or gen4.
> 
> Understand, as the inline function is very simple, it looks OK.
> >
> > >
> > > > +		/* Set translate base address index register */
> > > > +		xlat_off = XEON_GEN4_IM1XBASEIDX_OFFSET +
> > > > +			   mw_idx * XEON_GEN4_XBASEIDX_INTERVAL;
> > > > +		xlat_addr = hw->hw_addr + xlat_off;
> > > > +		rte_write16(rte_log2_u64(size), xlat_addr);
> > > > +	} else {
> > > > +		rte_write64(base, limit_addr);
> > > > +		rte_write64(0, xlat_addr);
> > > > +		return -ENOTSUP;
> > > > +	}
> > > Is the else branch necessary? As if neither gen3 or gen4, the init would fail.
> > > Would be better to print an ERR instead of just return NO support.
> >
> > I don't think so.
> > Yes. It will fail in init. Returning err is to stop other following
> > actions like in
> > intel_ntb_vector_bind() since it should be stopped.
> > And I'd like to keep them in one coding style. As to the print, I
> > think that can be upper layer's job to check the value and print err.
> > Choosing ENOTSUP is because that in init, if it's not supported hw, it
> > will return - ENOTSUP err.
> >
> I cannot say what you did is incorrect. But try to think it like this way:  according
> current API design, ntb raw device is allocated when driver probe, if init fails,
> raw device would be free. How the ops be called?

I'll add a err print later.
> 
> > > >
> > > >  	return 0;
> > > >  }
> > >