Hi Heinrich, I think I met some chicken and egg problem. Or I misunderstand something you mentioned.
So I tried board_fdt_blob_setup() and board_fix_fdt(). Both are too early. I need i2c to be drived first. And then I can use dm_i2c_probe() on different address to detect which extension board it is. However, in board_fdt_blob_setup() or board_fix_fdt(). i2c seems not working there. I can do the detection in board_late_init() but it is just too late for U-boot itself. Good for Linux kernel though. Sorry for my bad English. Measured boot is already working on my branch. But the way I implemented this is directly modify the dts of U-boot and assume the TPM extension board is always there. Thus this is not upstreamable. I think let me upstream some code by extension manager first (for linux kernel first). And then we can see how the detection is implemented and how to modify it for U-boot. Thanks, Paul Heinrich Schuchardt 於 2021/9/18 下午3:14 寫道: > > > On 9/18/21 8:54 AM, François Ozog wrote: >> Le sam. 18 sept. 2021 à 08:49, François Ozog >> <francois.o...@linaro.org> a >> écrit : >> >>> Hi Paul >>> >>> Too posting because I think we also need to address this at a higher >>> level. >>> >>> i think we discussed this topic quite a while back. I may be wrong >>> but it >>> may be Bill Mills who proposed to have an eeprom on the extensions >>> that the >>> carrier board can use to detect and fetch proper overlay. Another >>> way would >>> be that the contract between the extension board and the carrier board >>> includes an i2c accessible storage to fetch an overlay that would >>> identify >>> the board and give all details. >>> >> i just forgot to state that the mode is well known: SPD for DIMMs. >> >>> Bottom line, a software only solution seems not entirely satisfying. >>> In that suboptimal case, U-Boot shall be able to assemble a DT for >>> itself >>> and another for OS (may be same in some cases) through scripting. >>> And in >>> this case, come your questions below >>> >>> . >>> >>> Le sam. 18 sept. 2021 à 01:21, Ying-Chun Liu (PaulLiu) >>> <paul...@debian.org> >>> a écrit : >>> >>>> Hi all, >>>> >>>> >>>> I have some questions about how to implement extension board usage. >>>> My case is on imx8mm-cl-iot-gate. It can add three different types of >>>> extension boards. >>>> One of the extension boards is SPI extension which have 3 empty slots. >>>> And you can add >>>> some small boards onto it. One of them is a "TPM2" module. > > You could implement the weak function board_fdt_blob_setup() to detect > your addon boards and extend the devicetree. > > >>>> >>>> >>>> My first question is if I want to use tpm2 in U-boot for measured >>>> boot. >>>> How to implement this right? Currently I just modify the dts used by >>>> U-boot to let it drive > > Measured boot is provided in U-Boot v2021.10-rc4 based on TPMv2. Just > enable CONFIG_EFI_TCG2_PROTOCOL. > >>>> the extension board. And let it drive the TPM. But it is not good for >>>> upstreaming because >>>> when other types of extension boards installed then it is not working. >>>> Where to implement this? What is the best practice of this? >>> >>> >>>> The second question is about extension manager. >>>> I have read the extension.rst. I think I'll implement this anyway >>>> because then >>>> I can have a command to query what type of extension boards I have. >>>> And if the extension board is the 3 slots one. I can then detect which >>>> slot is the TPM. >>>> I'll implement this anyway because the "extension" command is >>>> convenient >>>> for users. >>>> But it seems to me that it only solves the problem for Linux kernel. >>>> It can apply a DTB Overlay to Linux DTB to let Linux knows we have >>>> that >>>> extension board. >>>> But it is too late for U-boot itself, right? >>>> >>>> >>>> The third question is I'm also dong SystemReady IR certificate. >>>> That means >>>> the dtb for Linux is directly provided by U-boot. We use U-boot dtb >>>> directly to Linux >>>> kernel. In this case, how to modify that dts dynamically to feed to >>>> the >>>> Linux kernel by >>>> the extension manager? > > U-Boot has a fdt command which you could use to apply overlays. Or > implement function board_fdt_blob_setup(). > > Best regards > > Heinrich > >>>> What is the best practice if I want to use U-boot dts for Linux in >>>> implementation? >>>> >>>> >>>> Thanks a lot. >>>> >>>> >>>> Yours, >>>> Paul >>>> >>>> >>>> -- >>> François-Frédéric Ozog | *Director Business Development* >>> T: +33.67221.6485 >>> francois.o...@linaro.org | Skype: ffozog >>> >>> -- >> François-Frédéric Ozog | *Director Business Development* >> T: +33.67221.6485 >> francois.o...@linaro.org | Skype: ffozog >> _______________________________________________ >> boot-architecture mailing list >> boot-architect...@lists.linaro.org >> https://lists.linaro.org/mailman/listinfo/boot-architecture >>
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