On 11/4/20 1:07 AM, Etienne Carriere wrote:
On Tue, 3 Nov 2020 at 16:53, Alex G. <mr.nuke...@gmail.com> wrote:
On 10/30/20 3:28 AM, Etienne Carriere wrote:
On Thu, 29 Oct 2020 at 15:33, Alex G. <mr.nuke...@gmail.com> wrote:
On 9/30/20 6:03 PM, Alex G. wrote:
Hi
I'm trying to wrap my head around the purpose of the following lines in
ft_system_setup():
if (!CONFIG_IS_ENABLED(OPTEE) ||
!tee_find_device(NULL, NULL, NULL, NULL))
stm32_fdt_disable_optee(blob);
Hi! Me again! Do we have a (good) reason for this, or should I submit a
patch to remove this problematic code?
Alex
My interpretation is "if optee is not running, delete the FDT node".
The problem is that tee_find_device() invokes device_probe(). This in
turn does an SMC call. This call results in an abort and reboot if optee
is not running in the first place.
So I don't think that tee_find_device() can be used as a check for "Is
optee running?". Exhibit B: Outside of mach-stm32mp, tee_find_device()
is used to obtain of a _working_ TEE node, not to ask if "is optee
running?".
My problem is that trying to start linux with CONFIG_OPTEE=y will cause
the bootm command to crash (log in appendix A):
load mmc 0:7 $fdt_addr_r boot/stm32mp157c-dk2.dtb
load mmc 0:7 0xc8000000 boot/utee
setenv bootm_boot_mode sec
bootm 0xc8000000 - $fdt_addr_r
What is the intent of calling tee_find_device() in an FDT fixup
function?
The scheme is the generic U-Boot implementation do copy OP-TEE
related nodes when found in its FDT to the FDT provided to Linux.
(called from common/image-fdt.c)
However stm32mp1 can be used with or without OP-TEE installed. To
get a generic stm32mp1/U-Boot image that support both configurations
(with and w/o OP-TEE installed), U-Boot FDT and config for this plaform
do enable OP-TEE but, at u-boot runtime, if we find OP-TEE's not present,
we remove the FTD node so that Linux does get it and expect OP-TEE
is present.
Do you have any ideas how to make it not crash (short of
commenting out the problem lines) ?
The crash seems due to that there is no secure monitor by the time
you have this sequence called. Secure monitor is the code that
handles the SMC. If none installed, SMCs ends nowhere and
likely badly crash the systel. If OP-TEE is not running but there
is a secure monitor loaded, it should not crash.
It seems to me that U-Boot does set up a secure monitor for
PSCI minimal support, so the U-Boot PSCI stack should
nicely handle the SMC to report that there is no OP-TEE installed.
Enabling CONFIG_ARMV7_PSCI should fix the issue I think.
Hi Etienne. I understand the reasoning behind this, and I agree that
things shouldn't break in theory. However,I just double-checked this
with master (7a8ac9df5d). I think we have a bug on our hands:
stm32mp15_basic_defconfig, with the following changes:
CONFIG_TEE=y
CONFIG_OPTEE=y
CONFIG_OPTEE_TZDRAM_SIZE=0x01000000
My apologies, I did'nt notice you use the _basic_defconfig.
With this defconfig, U-Boot cannot invoke OP-TEE services since OP-TEE
is booted only once U-Boot execution is completed (once bootm
command jumps to OP-TEE boot entry). So in this config U-Boot cannot
find the OP-TEE node.
Maybe ft_system_setup() (mach-stm32mp/fdt.c) should bypass OP-TEE
auto probing when CONFIG_BOOTM_OPTEE is enabled.
I'm seeing the following premise:
(a) Start out with a "clean" devicetree
(b) Add the 'optee' node (generic code)
(c) Remove the 'optee' node (stm32mp1 specific)
This seems odd to me for two reasons:
1. The code does more work than it needs to
2. stm32mp behaves differently than other platforms
The way I would approach this is to adjust the heuristic in step (b).
This can be found in include/tee/optee.h:
if CONFIG_OPTEE and CONFIG_OF_LIBFDT
add optee node
else
do nothing
If there's no need to do step (b), why do both steps (b) and (c) instead
of doing nothing?
Given that there isn't a situation where step (c) makes sense, I propose
that we remove stm32_fdt_disable_optee() entirely. The worst case is
that the 'optee' node stays up, linux is booted in non-secure mode, and
throws an -ENODEV in optee_probe() -- but otherwise the system boots.
I can prepare a patch, pending Patrick's analysis.
That would probably require to change stm32mp15_trusted_defconfig
to explicitly disable CONFIG_BOOTM_OPTEE, since this config
does not allow booting OP-TEE from U-Boot.
Patrick, your opinion?
FYI Alex, stm32mp15_basic_defconfig is not well suited to boot OP-TEE.
Consider using stm32mp15_trusted_defconfig instead. The "Trusted"
means U-Boot is booted after secure world. SPL could still be used
to load/boot OP-TEE but stm32mp15_trusted_defconfig does not
provide such support in current U-Boot. TF-A is an alternative to SPL
in this case.
I have boot timing constraint of one to a graphical userspace
application. The TF-A boot flow blows my boot time budget. I think
trusted_defconfig assumes TF-A instead of SPL, so I didn't dig into it.
The fast graphical boot is a use case that I don't think has been
addressed for STM32MP. I'm currently implementing:
SPL -> OPTEE -> Linux -> Userspace graphics app
This flow doesn't really require CONFIG_BOOTM_OPTEE. However, I'm still
interested in a proper for the sake of consistency across platforms.
Alex
br,
etienne
# CONFIG_SYSRESET_CMD_POWEROFF is not set
I double-checked that CONFIG_ARMV7_PSCI is indeed set. The following
sequence will cause a bad mode abort:
> load mmc 0:7 $loadaddr boot/uImage
> load mmc 0:7 $fdt_addr_r boot/stm32mp157c-dk2.dtb
> setenv bootargs console=ttySTM0 root=/dev/mmcblk0p7
> bootm $loadaddr - $fdt_addr_r
Alex
Regards,
Etienne
Alex
Appendix A: u-boot log after bootm command
## Booting kernel from Legacy Image at c8000000 ...
Image Name:
Created: 2020-09-28 20:58:56 UTC
Image Type: ARM Trusted Execution Environment Kernel Image
(uncompressed)
Data Size: 349276 Bytes = 341.1 KiB
Load Address: fdffffe4
Entry Point: fe000000
Verifying Checksum ... OK
Loading Kernel Image
## Flattened Device Tree blob at c4000000
Booting using the fdt blob at 0xc4000000
Loading Device Tree to cffef000, end cffff5e2 ... OK
<BOARD RESETS WITHOUT USER INPUT>
U-Boot SPL 2020.10-rc4 (Sep 20 2020 - 23:46:47 +0000)
Model: STMicroelectronics STM32MP157C-DK2 Discovery Board
