Hi Michael, Gentle reminder on this patch set.
Regards, Sahil Malhotra > -----Original Message----- > From: Sahil Malhotra (OSS) > Sent: Friday, February 4, 2022 4:58 PM > To: Michael Walle <[email protected]>; Sahil Malhotra (OSS) > <[email protected]> > Cc: ZHIZHIKIN Andrey <[email protected]>; Clément > Faure <[email protected]>; Gaurav Jain <[email protected]>; > Pankaj Gupta <[email protected]>; Priyanka Jain > <[email protected]>; [email protected]; Varun Sethi > <[email protected]>; Ye Li <[email protected]> > Subject: RE: [PATCH 1/2] fsl-layerscape: add dtb overlay feature > > Hi Michael, > > Sorry for delayed response. > Please find my response inline. > > > -----Original Message----- > > From: Michael Walle <[email protected]> > > Sent: Thursday, January 6, 2022 1:10 PM > > To: Sahil Malhotra (OSS) <[email protected]> > > Cc: ZHIZHIKIN Andrey <[email protected]>; Clément > > Faure <[email protected]>; Gaurav Jain <[email protected]>; > > Pankaj Gupta <[email protected]>; Priyanka Jain > > <[email protected]>; [email protected]; Varun Sethi > > <[email protected]>; Ye Li <[email protected]> > > Subject: Re: [PATCH 1/2] fsl-layerscape: add dtb overlay feature > > > > Hi Sahil, > > > > Am 2022-01-06 07:09, schrieb Sahil Malhotra (OSS): > > > > >> I don't know I follow. u-boot and linux should have the same device > > >> tree; regardless if that device is used or not. So applying the > > >> overlay just for linux isn't enough here. > > > Ok, I don't think that as of now, in all platforms uboot and linux > > > have same devie tree. > > > > That doesn't mean it is ok to diverge again. I put a lot of effort in > > syncing uboot's LS1028A device tree with linux. > Yes, that’s true we should not diverge again if they are already synced. > > > > > But I will try to address your concern, but I don’t know how to > > > apply overlay to dtb which is embedded in u-boot binary, Can you > > > please point me to one reference which is doing this thing, I will > > > take reference from there. > > > > Sorry I can't advise you with that. There is board_fix_fdt() maybe > > that will help. But I'm not conviced this is the correct approach, see > > below. > Ok, I looked at the board_fix_fdt() and in that we can put the code for > modifying the uboot DTB. > But the same overlay which we are going to apply on linux DTB should get > applied On uboot DTB, and that can happen only when we have same DTBs > both in Linux and u-boot. > > I checked the uboot and Linux DTBs for LS platforms, except LS1028, all other > platforms have a lot of difference in them. > > So we will not be able to apply the same DTB overaly which we get from OP- > TEE on both Linux and uboot. > > For now this can only happen for LS1028 platform, if you want we can do this, > But it will be incomplete in my opinion as it will not enable all the boards. > We need to work on them again. > > > > > >> > We don't use DTB in OP-TEE, but when we use CAAM in OP-TEE, > > >> > OP-TEE reserves One Job Ring for its use and that is communicated > > >> > to Kernel using DTB overlay. > > >> > > > >> >> what if the overlay doesn't match the dtb? > > >> > I didn't get this point, can you please elaborate a little. > > >> > > >> You are merging a dtb fragment with an unknown dtb, right? Who says > > >> they match? you might have an old dtb where the supplied dtb > > >> fragment doesn't make any sense. > > >> > > >> I might be missing something here. Eg. where is the linux dtb > > >> supposed to come from? This patchset is really missing an example > > >> and a description how things should work. > > > If supplied DTB does not match with DTB overlay fragment. then > > > overlay will not get applied. > > > > I don't think this is what happens here. fdt_overlay_apply() will mark > > the fdt as damaged and there will be no fdt at all. > Ok, got your point, If we have fragment in DTB overlay to modify let's say > `status` of CAAM job ring, and CAAM job ring node does not exist in the DTB > on which overlay is going to be applied, In that case the DTB will be marked > as > damaged and it will stop booting of the board, right ? > But how can we make sure that DTB overlay and DTB on which DTB overlay is > applied are compatible ? > Maybe some DTB version check or something like that, when OP-TEE creates > a DTB overlay, It indicates in the overlay that this can be applied on only > DTBs > with version more than `X` > > > > > We don't have any control on where user picks the DTB, but we can only > > > make sure DTB overlay feature must work with DTBs which are > upstreamed > > > If user makes its own customized DTB, we cannot make sure that things > > > will work. > > > > Again. Is there any documentation on how this should all work together? > > Where does optee get its device tree from? Shouldn't it be the same > device > > tree as u-boot and linux? Shouldn't optee modify the device tree in place > > before jumping back to u-boot? > Here on LS platforms: Boot Flow is like ATF-> OP-TEE-> ATF->Uboot-> Linux > > Currently for LS platforms, OP-TEE don't use DTBs except for LX2160A. > And I am talking about the other platforms except LX2160 for now. > So all peripherals base addresses are currently hardcoded. > > But OP-TEE uses some of the peripherals, and this information needs to > be passed to following components uboot and linux so that they don't use > the same peripherals. > > One of the case is CAAM Job Ring. OP-TEE always use CAAM Job Ring 3, and it > needs to communicate this thing to following components uboot so that they > don’t > try to use the same peripherals as used by OP-TEE, > So, we enabled DTB_OVERLAY option in OP-TEE and will write CAAM Job Ring > 3 to be > disabled in that DTB overlay. > > The address where this DTB overlay will be created is passed by ATF which > ATF will > pass on to uboot also. > > When control reaches uboot, It will use that DTB overlay and apply it on > Linux DTB > which we passed via tftp on board. > > Currently there is no common DTB which is being used by all the components, > OP-TEE, Uboot, Linux all are using their own copies of DTB. > > Hope I answered your queries, Please let me know if you need more > information. > > > Andrey, do you know how this works on imx? > Actually, I took reference from imx only, They are also just applying DTB > overlay on linux DTB as of now. > They are not modifying the uboot DTB according to the DTB overlay. > > > Regards, > Sahil Malhotra
