[dpdk-dev] [PATCH v4] ixgbe_pmd: enforce RS bit on every EOP descriptor for devices newer than 82598

[Thomas Monjalon]

Any Follow-up to this discussion?
Should we mark this patch as rejected?

2015-08-24 11:11, Vlad Zolotarov:
> On 08/20/15 18:37, Vlad Zolotarov wrote:
> > According to 82599 and x540 HW specifications RS bit *must* be
> > set in the last descriptor of *every* packet.
> >
> > Before this patch there were 3 types of Tx callbacks that were setting
> > RS bit every tx_rs_thresh descriptors. This patch introduces a set of
> > new callbacks, one for each type mentioned above, that will set the RS
> > bit in every EOP descriptor.
> >
> > ixgbe_set_tx_function() will set the appropriate Tx callback according
> > to the device family.
> 
> [+Jesse and Jeff]
> 
> I've started to look at the i40e PMD and it has the same RS bit 
> deferring logic
> as ixgbe PMD has (surprise, surprise!.. ;)). To recall, i40e PMD uses a 
> descriptor write-back
> completion mode.
> 
>  From the HW Spec it's unclear if RS bit should be set on *every* descriptor
> with EOP bit. However I noticed that Linux driver, before it moved to 
> HEAD write-back mode, was setting RS
> bit on every EOP descriptor.
> 
> So, here is a question to Intel guys: could u, pls., clarify this point?
> 
> Thanks in advance,
> vlad