Hi Sahil,
(and happy new year ;-)
On Thu, 6 Jan 2022 at 07:09, Sahil Malhotra (OSS) < sahil.malhotra@oss.nxp.com> wrote:
Hi Michael,
-----Original Message----- From: Michael Walle michael@walle.cc Sent: Thursday, December 23, 2021 3:05 PM To: Sahil Malhotra (OSS) sahil.malhotra@oss.nxp.com Cc: ZHIZHIKIN Andrey andrey.zhizhikin@leica-geosystems.com; Clément
Faure
clement.faure@nxp.com; Gaurav Jain gaurav.jain@nxp.com; Pankaj Gupta pankaj.gupta@nxp.com; Priyanka Jain priyanka.jain@nxp.com; u- boot@lists.denx.de; Varun Sethi V.Sethi@nxp.com; Ye Li ye.li@nxp.com Subject: Re: [EXT] Re: [PATCH 1/2] fsl-layerscape: add dtb overlay
feature
Hi Sahil,
Am 2021-12-23 09:46, schrieb Sahil Malhotra (OSS):
-----Original Message----- From: U-Boot u-boot-bounces@lists.denx.de On Behalf Of Michael Walle Sent: Monday, December 20, 2021 6:23 PM To: Sahil Malhotra (OSS) sahil.malhotra@oss.nxp.com Cc: ZHIZHIKIN Andrey andrey.zhizhikin@leica-geosystems.com; Clément Faure clement.faure@nxp.com; Gaurav Jain gaurav.jain@nxp.com; Pankaj Gupta pankaj.gupta@nxp.com; Priyanka Jain priyanka.jain@nxp.com; u-boot@lists.denx.de; Varun Sethi V.Sethi@nxp.com; Ye Li ye.li@nxp.com Subject: [EXT] Re: [PATCH 1/2] fsl-layerscape: add dtb overlay feature
Caution: EXT Email
Hi Sahil,
Am 2021-12-10 07:33, schrieb Sahil Malhotra (OSS):
DT nodes can be statically disabled if we know that they are held by HAB and are not released to NS World.
OP-TEE does set the status itself via dt_enable_secure_status(), which should present the properly configured FDT when U-Boot takes
over.
Yes, OP-TEE set the status by dt_enable_secure_status() in DTB overlay which gets merged with DTB provided for Linux bootup and then Linux boots with merged DTB. But u-boot uses the DTB embedded in its image. How can we modify that DTB or merge DTB overlay passed by OP-TEE with uboot DTB ?
But then u-boot has the "wrong" dtb. What is the reason, there is an overlay instead of a whole dtb? what if the overlay doesn't match the dtb?
"wrong" dtb means that uboot will not be aware of CAAM job ring which is taken by OP-TEE and uboot on LS platforms currently use JR0, which is not being used by any other entity in LS bootflow.
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. 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.
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. 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.
Elaborating on a broader context: who is the user in U-Boot? In
desktops/laptops context, I understand the user could be the desktop/laptop owner but based on my limited understanding of Chrome, users are quite constrained in what they can do (allowing the user to play with DT is a recipe for costly support). In the embedded case, is the user the one who makes a board based on the SoC ? the product maker that uses the board for a particular solution ? the integrator who places the board in a larger product ? the larger product maker ? the larger product owner ? the larger product maintenance guy? ultimately I think there is a need to empower a number of actors listed above who will take the responsibility based on consultation from the software value chain. All this to say I believe we lack vocabulary to identify actors in the firmware software value chain: has anyone already tried to formalize this?
Regards,
Sahil Malhotra