In my arm-trusted-firmware directory, I have a local branch named GRU_spectre that is based of the upstream branch cros/firmware-gru-8785.B with the five patches ending in https://chromium-review.googlesource.com/909913 on top of it. I then ran the following command:

$ cros tryjob -b firmware-gru-8785.B --notests -p chromiumos/third_party/arm-trusted-firmware:GRU_spectre gru-firmware-tryjob
Verifying patches...
Submitting tryjob...
Uploading patch chromiumos/third_party/arm-trusted-firmware:GRU_spectre:b5b7e13b "AArch32: Fix SCTLR context initialization"
Uploading patch chromiumos/third_party/arm-trusted-firmware:GRU_spectre:c467d412 "rockchip: fix the scu idle for rk3399"
Uploading patch chromiumos/third_party/arm-trusted-firmware:GRU_spectre:149016d1 "rockchip/rk3399: improve gpio driver and support get pull mode function"
Uploading patch chromiumos/third_party/arm-trusted-firmware:GRU_spectre:8d40c71a "rockchip: support disable/enable specific gpio when suspend/resume"
Uploading patch chromiumos/third_party/arm-trusted-firmware:GRU_spectre:fc23b1c9 "rockchip: set gpio2 ~ gpio4 to input and pull none mode"
Uploading patch chromiumos/third_party/arm-trusted-firmware:GRU_spectre:c7b221b7 "Revert "rockchip: fix the scu idle for rk3399""
Uploading patch chromiumos/third_party/arm-trusted-firmware:GRU_spectre:26d02464 "rockchip: fixes the gic panic for rk3399 resume"
Uploading patch chromiumos/third_party/arm-trusted-firmware:GRU_spectre:89048b85 "REDO: rockchip: fix the scu idle for rk3399"
Uploading patch chromiumos/third_party/arm-trusted-firmware:GRU_spectre:fe553bb1 "rockchip: rk3399: return error value for every RK_SIP_DRAM_CFG SMC call"
Uploading patch chromiumos/third_party/arm-trusted-firmware:GRU_spectre:88ff41c1 "Flush `psci_plat_pm_ops` after initialization"
Uploading patch chromiumos/third_party/arm-trusted-firmware:GRU_spectre:3a87f6a0 "rockchip: fixes the clock select and divide register for rk3399"
Uploading patch chromiumos/third_party/arm-trusted-firmware:GRU_spectre:b9004702 "rockchip: SIP call use 32 bit return value for rk3399"
Uploading patch chromiumos/third_party/arm-trusted-firmware:GRU_spectre:40a7edd9 "rockchip: optimize the link mechanism for SRAM code"
Uploading patch chromiumos/third_party/arm-trusted-firmware:GRU_spectre:9d7cef25 "rockchip: add M0 source code and build system for RK3399"
Uploading patch chromiumos/third_party/arm-trusted-firmware:GRU_spectre:26e84bdb "rockchip: clear the power mode status via M0"
Uploading patch chromiumos/third_party/arm-trusted-firmware:GRU_spectre:b3fcad04 "Merge "rockchip: SIP call use 32 bit return value for rk3399" into firmware-gru-8785.B"
16:55:33: ERROR: cros tryjob failed before completing.
16:55:33: ERROR: chromiumos/third_party/arm-trusted-firmware:GRU_spectre:b3fcad04 "Merge "rockchip: SIP call use 32 bit return value for rk3399" into firmware-gru-8785.B" failed: Branch chromiumos/third_party/arm-trusted-firmware:GRU_spectre contains merge result b3fcad046bb80be9a9e9be5ef033afe54a3cc3f9!

First of all, it's uploading lots of patches it really shouldn't. My guess is that these are the differences between m/master and cros/firmware-gru-8785.B, because it somehow doesn't realize that the non-master branch my local branch is based off is the same branch as I'm passing with -b. Second of all, it's failing for some reason.

I read the warning that -p is considered buggy, but I hope the plan is to transition it to non-buggy state some day so I'm filing this for posterity.