Le 03/01/2017 à 11:47, Rafal Ozieblo a écrit : >> From: Harini Katakam [mailto:harinikatakamli...@gmail.com] >> Sent: 3 stycznia 2017 06:06 >> Subject: Re: [RFC PATCH net-next v4 1/2] macb: Add 1588 support in Cadence >> GEM. >> >> Hi Richard, >> >> On Mon, Jan 2, 2017 at 9:43 PM, Richard Cochran <richardcoch...@gmail.com> >> wrote: >>> On Mon, Jan 02, 2017 at 03:47:07PM +0100, Nicolas Ferre wrote: >>>> Le 02/01/2017 à 12:31, Richard Cochran a écrit : >>>>> This Cadence IP core is a complete disaster. >>>> >>>> Well, it evolved and propose several options to different SoC >>>> integrators. This is not something unusual... >>>> I suspect as well that some other network adapters have the same >>>> weakness concerning PTP timestamp in single register as the early >>>> revisions of this IP. >>> >>> It appears that this core can neither latch the time on read or write, >>> or even latch time stamps. I have worked with many different PTP HW >>> implementations, even early ones like on the ixp4xx, and it is no >>> exaggeration to say that this one is uniquely broken. >>> >>>> I suspect that Rafal tend to jump too quickly to the latest IP >>>> revisions and add more options to this series: let's not try to pour >>>> too much things into this code right now. >>> >>> Why can't you check the IP version in the driver? >> >> There is an IP revision register but it would be probably be >> better to rely on "caps" from the compatibility strings - to cover SoC >> specific >> implementations. Also, when this extended BD is added (with timestamp), >> additional words will need to be added statically which will be >> consistent with Andrei's CONFIG_ checks. > We can distinguish IP cores with and without PTP support by reading > Design Configuration Register. But to distinguish IP cores with > timestamps in buffer descriptors and which support only event > registers, we can only check IP version by reading the revision ID > register and base on that. > I agree with Harini, compatibility strings could be better. But we > might end up with many different configuration in the future.
Compatibility strings and associated configurations are cheap. It's not a problem to have many different configurations and clearer for this particular "composite" feature. > We could use only descriptor approach but there are many Atmel's > cores on the market which support only event registers. Yes and once in silicon, it's hard to modify ;-) Regards, -- Nicolas Ferre
