Dear Rob, Thanks for your comments. On Mon, 2018-11-26 at 15:46 -0600, Rob Herring wrote: > On Fri, Nov 23, 2018 at 09:31:16AM +0800, biao huang wrote: > > Dear Andrew, > > > > Thanks for you remind. > > > > Sincerely, I respect any comment from any reviewer. If I didn't reply > > for any comment, really sorry for that. > > > > As to this "tx-delay" issue, the following reply in v3 maybe ignored. > > https://lkml.org/lkml/2018/11/19/158 > > > > "the delay time in mediatek dwmac design is not so accurate, > > the current mt2712 and the following ICs will not use the > > same delay design, but will use stages to indicate different > > delay time. > > so maybe "mediatek.tx-delay" represent the delay stage is a > > good choice" > > > > And to make it clearer here. > > > > In mt2712, there are two delay macro circuit: named fine-tune and > > coarse-tune. > > a. fine-tune, 170+/-50ps per stage, total 32 stages > > b. coarse-tune, 0.55+/-0.2ns per stage, total 32 stages > > If we only consider mt2712, delay in fine-tune select a integer > > multiple of 170ps, delay in coarse-tune select a integer multiple of > > 550ps, for stage 0~31, the delay in fine-tune will not have the same > > value with that in coarse-tune. > > OK, It seems the property "fine-tune" can be eliminated . > > > > But the following ic will not have the same accuracy as mt2712, > > and maybe will not have two delay macro circuit to be selected. > > New IC will have new compatible string then. If it is different, then > likely these properties would have to change or have different meaning > unless you use time. > OK, I'll use tx-delay-ps instead of tx-delay. > > 1. assume two delay macro circuit in the following ic, > > fine-tune, 100ps per stage, coarse-tune, 0.55ns per stage, > > if we want delay 2.2ns, fine-tune will get a 22, and coarse-tune get a > > 4. We can't distinguish which delay macro we are choosing. > > Why wouldn't you just choose fine-tune for anything less than the max > range (3200ps in this example) and course for greater than 3100ps. > The fine-tune circuit and coarse-tune circuit are parallel, and fine-tuen is a select switch. It depends on users to choose which circuit is take effect. I shouldn't assume users would choose fine-tune when delay < 3200ps, and coarse for > 3100ps. so, tx-delay-ps will be chosen, and "fine-tune" boolean property should be remained as a indicator. > > 2. assume only one delay macro circuit is used, a similar case as 1 > > will also increase the complexity of driver. > > Then, we need define more flag property to know which delay macro we > > are handling. > > > > The common things for all delay macro circuit in MediaTek mac design is > > the stages, not the accuracy. so if we maintain stage info in "mediatek, > > tx-delay", we only need care which stage we should choose. > > And for each IC, we will recommend a best stage as a candidate. > > What if you had a 3rd delay circuit? > OK, tx-delay-ps will be a meaningful property. If more delay circuit is added, fine-tune property(boolean --> u32) can still be a indicator. > > Above is my personal opinion, may be my understanding is wrong, > > welcome for further discussion. > > > > Thanks a lot.
