Messages in this thread | | | Date | Sat, 7 Jan 2023 01:29:05 +0200 | From | Vladimir Oltean <> | Subject | Re: [PATCH net-next v5 4/4] phy: aquantia: Determine rate adaptation support from registers |
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On Fri, Jan 06, 2023 at 06:21:26PM -0500, Sean Anderson wrote: > On 1/6/23 18:03, Vladimir Oltean wrote: > > On Thu, Jan 05, 2023 at 05:46:48PM +0000, Russell King (Oracle) wrote: > >> On Thu, Jan 05, 2023 at 07:34:45PM +0200, Vladimir Oltean wrote: > >> > So we lose the advertisement of 5G and 2.5G, even if the firmware is > >> > provisioned for them via 10GBASE-R rate adaptation, right? Because when > >> > asked "What kind of rate matching is supported for 10GBASE-R?", the > >> > Aquantia driver will respond "None". > >> > >> The code doesn't have the ability to do any better right now - since > >> we don't know what sets of interface modes _could_ be used by the PHY > >> and whether each interface mode may result in rate adaption. > >> > >> To achieve that would mean reworking yet again all the phylink > >> validation from scratch, and probably reworking phylib and most of > >> the PHY drivers too so that they provide a lot more information > >> about their host interface behaviour. > >> > >> I don't think there is an easy way to have a "perfect" solution > >> immediately - it's going to take a while to evolve - and probably > >> painfully evolve due to the slowness involved in updating all the > >> drivers that make use of phylink in some way. > > > > Serious question. What do we gain in practical terms with this patch set > > applied? With certain firmware provisioning, some unsupported link modes > > won't be advertised anymore. But also, with other firmware, some supported > > link modes won't be advertised anymore. > > Well, before the rate adaptation series, none of this would be > advertised. I would rather add advertisement only for what we can > actually support. We can always come back later and add additional > support.
Well, yes. But practically, does it matter that we are negotiating a link speed that we don't support, when the effect is the same (link doesn't come up)? The only practical case I see is where advertising e.g. an unsupported 2.5G would cause the link to not establish at a supported 1G. But as you say, I don't think this will be the case with the firmware provisioning that Tim gave as an example?
> > IIUC, Tim Harvey's firmware ultimately had incorrect provisioning, it's > > not like the existing code prevents his use case from working. > > The existing code isn't great as-is, since all the user sees is that we > e.g. negotiated for 1G, but the link never came up. > > --Sean
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