Hello Geert, Thomas On Tue, 19 Oct 2021 22:05:41 +0200 Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote: > Hi Thomas, > > On Tue, Oct 19, 2021 at 5:57 PM Thomas Petazzoni > <thomas.petazzoni@xxxxxxxxxxx> wrote: > > On Tue, 19 Oct 2021 17:41:49 +0200 > > Andrew Lunn <andrew@xxxxxxx> wrote: > > > > When people update the kernel version don't they update also the > > > > devicetree? > > > > > > DT is ABI. Driver writers should not break old blobs running on new > > > kernels. Often the DT blob is updated with the kernel, but it is not > > > required. It could be stored in a hard to reach place, shared with > > > u-boot etc. > > > > Right, but conversely if someone reads the DT bindings that exists > > today, specifies phy-mode = "rgmii-rxid" or phy-mmode = "rmgii-txid", > > Today == v5.10-rc1 and later? > > > this person will get incorrect behavior. Sure a behavior that is > > backward compatible with older DTs, but a terribly wrong one when you > > write a new DT and read the DT binding documentation. This is exactly > > the problem that happened to us. > > If you write a new DT, you read the DT binding documentation, and > "make dtbs_check" will inform you politely if you use the legacy/wrong > DT (i.e. lacking "[rt]x-internal-delay-ps")? Indeed this command will inform the missing required "[rt]x-internal-delay-ps". I am not use to that command, as it seems to check all the devicetree each time where I want only to check one. > > The current driver is backwards-compatible with the legacy/wrong DTB. > The current DT bindings (as of v5.10-rc1), using "[rt]x-internal-delay-ps" > are correct. > Or am I missing something here? You are correct. > > BTW, it's still not clear to me why the inversion would be needed. > Cfr. Andrew's comment: > > | So with rgmii-rxid, what is actually passed to the PHY? Is your > | problem you get twice the delay in one direction, and no delay in the > | other? Yes, it was the problem I got. The PHY I use have RX delay enabled by default, currently the PHY driver does not support delay configuration, therefore I let the MAC handle TX delay. I have stumbling over that legacy/wrong DTS on the old Kernel. Regards, Köry
