I am trying to add support in mainline for a tablet based on Exynos
5420 (Samsung Galaxy Tab S). For this tablet, CCI has to be disabled,
and with that the device then hangs during
exynos_smc(SMC_CMD_CPU1BOOT, cpu, 0, 0),
which is run in the cpu_boot secure-firmware function. If the call is
skipped, then four out of eight CPUs are brought up, which is the same
as on exynos5420-arndale-octa [1] which also has disabled CCI.
Based on Samsung's kernel sources, it seems like the SMC_CMD_CPU1BOOT
call is only needed on Exynos4 and Exynos5250 devices [2], on other
SoC models the call is skipped. To test if the call seem to do
anything, I booted exynos5422-odroid-xu4 with disabled CCI and with or
without the SMC_CMD_CPU1BOOT call. The result in both cases were the
same: the first four CPUs were brought up.
To further investigate if the SMC_CMD_CPU1BOOT call is handled we need
to dig into the trustzone firmware. The trustzone firmware used in
exynos5410-odroid-xu has been to a large part reverse engineered [3],
and by comparing with sboot/tzsw in mainline devices it can be seen
that similar trustzone firmware is used in several. Out of those, the
SMC_CMD_CPU1BOOT call seem to be only handled in Exynos4 devices.
Here's a table summarising the findings for the mainline devices that
have a secure-firmware node (Exynos3 devices omitted). An extra 4212
device has been included to get a datapoint for that SoC as well.
.----------------------.--------------.--------------.--------------.
| Device (exynos-) | Similar tzsw | CPU1BOOT SMC | sboot/tzsw |
| | to 5410? | handled? | source |
.----------------------.--------------.--------------.--------------.
4212 galaxy tab 3 | yes | yes | T310XXSBQB2
4412-i9300 | yes | yes | I9300XXUGPE1
4412-i9305 | yes | yes | I9305XXUFPB1
4412-itop-elite | not checked | |
4412-n710x | not checked | |
4412-odroid{x,x2,u3} | yes | yes | wiki.odroid.com/_media/en/boot.tar.gz
4412-origen | no | don't know | Linaro's origen hwpack 20130130
4412-p4note-n8010 | not checked | |
4412-trats2 | not checked | |
5410-odroidxu | yes | no | github.com/hsnaves/exynos5410-firmware
5410-smdk5410 | not checked | |
5420-arndale-octa | yes | no | Linaro's arndale-octa hwpack 20140323
5422-odroid-xu{3,4} | yes | no | Hardkernel's u-boot 2020.01 branch
"Similar tzsw" above means that the secure monitor calls seem to be
handled in the same way as for exynos5410-odroid-xu, in a quite
easy-to-spot function (see patch for what it looks like).
For the tablet I am actually interested in, the trustzone firmware
looks very different, and I have not been able to locate where/how the
secure monitor calls are handled.
Nevertheless, since the call seem to only be handled in trustzone
firmware for Exynos4, and since exynos5422-odroid-xu4 behaves the same
with or without this secure monitor call, I *think* it should be safe
to only run it on the devices where we know that it is handled.
[1] https://krzk.eu/#/builders/32
[2] https://github.com/LineageOS/android_kernel_samsung_exynos5420/blob/cm-14.1/arch/arm/mach-exynos/platsmp.c#L225-L229
[3] https://github.com/hsnaves/exynos5410-firmware
Henrik Grimler (1):
ARM: exynos: only do SMC_CMD_CPU1BOOT call on Exynos4
arch/arm/mach-exynos/firmware.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
base-commit: 3e4d9032d1a223488456f82d05cfe5519962f344
prerequisite-patch-id: f0f30752eb24b3515eee0a8d7bcf043e2cb084ad
--
2.34.1
