On Fri, Aug 11, 2023 at 11:43:01AM -0400, Sean Anderson wrote: > >> > > Here is an illustrative example (sorry, I don't have a board with the > >> > > right refclk on that PLL, to verify all the way): > >> > > > >> > > ... snip ... > >> > > >> > (which of course complicates the process of building the PBIs...) > >> > >> Maybe this is the language barrier, but what are you trying to say here? > > > > I said that I don't understand. Can you please clarify what you were > > trying to transmit with this comment? > > Well, right now I produce my RCWs by generating a second RCW with e.g. > 1133 replaced by 3333. But doing this is a more involved change. Just a > minor issue, really. Ok, so a comment related to your private build environment, and not a counter-argument to the solution. It wasn't clear. > That said, I don't think this is the best approach moving forward. > Much like many other platforms, users should be able to plug in an SFP > module and Linux should configure things appropriately. An RCW > approach requires some kind of configuration tool to swap out the > bootloaders, which isn't as good of a user experience. I am quite familiar with the SFP use case you are talking about. SolidRun requested that on LX2160 with the Lynx 28G driver, and that works fine there. What I am proposing is for the exact same approach to be used with Lynx 10G as well. Let me explain that approach, because your mention of "swapping out the bootloaders" makes it appear as if you are not visualising what I am proposing. The Lynx SerDes family has 2 PLLs, and more lanes (4 or 8). Each lane uses one PLL or the other, to derive its protocol frequency. Through the RCW, you provision the 2 PLL frequencies that may be used by the lanes at runtime. The Lynx 28G SerDes driver reads the PLL frequencies in lynx_28g_pll_read_configuration(), and determines the interface modes supportable by each PLL (this is used by phylink). But it never changes those PLL frequencies, since that operation is practically impossible in the general sense (PLLs are shared by multiple lanes, so changing a PLL frequency disrupts all lanes that use it). So, you see, the RCW approach that I am proposing is not the RCW approach that you are thinking about. I was never suggesting to swap the bootloader when the user plugs in a different SFP. I am just suggesting that the RCW is provisioned for 2 different PLL frequencies, and those PLL frequencies give you 2 networking protocol speed options. Depending on what each lane needs (the information comes from phylink), you can move each lane to one PLL or the other, at runtime, in the Linux SerDes driver, to support the speeds of 1G and 10G, or 10G and 25G. You can't get more than 2 speeds at the same time with just 2 PLLs, and this is an intrinsic limitation of the fact that there are just 2 PLLs. If the RCW and board do not provision the PLL frequencies for more than 1 lane speed, then no dynamic protocol switching is possible, and the supported_interfaces of each lane contains a single bit: the reset-time protocol.
