Hi Andrzej

I think recent patch: https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/3493 which is currently in review may be solution for your issue where SCU presence is being checked before accessing CLUSTERCFR_EL1 register.

Thanks Manish Badarkhe From: TF-A tf-a-bounces@lists.trustedfirmware.org on behalf of "Witkowski, Andrzej via TF-A" tf-a@lists.trustedfirmware.org Reply to: "Witkowski, Andrzej" andrzej.witkowski@intel.com Date: Monday, 1 June 2020 at 19:38 To: "tf-a@lists.trustedfirmware.org" tf-a@lists.trustedfirmware.org Cc: "Witkowski, Andrzej" andrzej.witkowski@intel.com, "Lessnau, Adam" adam.lessnau@intel.com Subject: [TF-A] Unhandled Exception at EL3 in BL31 for Neoverse N1 with direct connect of DSU

Hi,

I work on project which uses ARM CPU Neoverse N1 with direct connect of DSU. I noticed the following error “Unhandled Exception at EL3” in BL31 bootloader after switching from ATF 2.1 to 2.2. The root cause is that after invoking neoverse_n1_errata-report function in lib/cpus/aarch64/neoverse_n1.S file and reaching the line 525, the function check_errata_dsu_934 in lib/cpus/aarch64/dsu_helpers.S file is always invoked regardless of whether ERRATA_DSU_936184 is set to 0 or to 1. In our case, ERRATA_DSU_936184 := 0.

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[cid:image002.png@01D6384E.C183C050]

Neoverse N1 with direct connect version of DSU doesn’t contain SCU/L3 cache and CLUSTERCFR_EL1 register. The error “Unhandled Exception at EL3” appears in BL31 bootloader during attempt to read the CLUSTERCFR_EL1 register which doesn’t exist in our RTL HW.

Andrzej Witkowskie Intel Technology Poland

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