Open-Source Adreno Driver Gets A6xx "Zap" Shader - Lets GPU Leave Secure Mode

Written by Michael Larabel in Hardware on 12 March 2019 at 02:49 PM EDT. Add A Comment
Thanks to the Qualcomm / Linux Foundation Code Aurora, patches are pending for the Freedreno MSM DRM kernel driver to allow the latest-generation Adreno 600 series hardware to leave its "secure" mode.

While the Adreno A6xx series support has come together nicely in recent months for the DRM kernel driver and Freedreno Gallium3D driver, currently it's stuck in the "secure" mode at boot that restricts memory access and other safeguards... Part of the overall industry trend of tightening up access to the graphics processors in the name of better security.

With the latest patches, there is a "zap" shader to allow for Adreno 600 series hardware to leave this secure mode. The implementation is similar to the existing Adreno 500 series support and allows a way out for the GPU from its secure mode via a series of commands, since some bootloaders restrict access otherwise to the register needed to let the GPU leave the secure mode.

The zap shader clears out the internal GPU settings as it transitions to the "in-secure" mode. The patches restructure about one hundred lines of code in order to get the zap shader support extended from A5xx to A6xx graphics hardware found in the latest Snapdragon SoCs. Given the current timing, we'll likely see this work merged for Linux 5.2.
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