On Thu, Jan 14, 2021 at 4:05 PM AngeloGioacchino Del Regno
[off-list ref] wrote:

Il 14/01/21 23:37, Jeffrey Hugo ha scritto:

quoted

On Thu, Jan 14, 2021 at 3:13 PM AngeloGioacchino Del Regno
[off-list ref] wrote:

quoted

The GPU IOMMU depends on this clock and the hypervisor will crash
the SoC if this clock gets disabled because the secure contexts
that have been set on this IOMMU by the bootloader will become
unaccessible (or they get reset).
Mark this clock as critical to avoid this issue when the Adreno
GPU is enabled.

You should go review the last attempt to do this -
https://lkml.org/lkml/2019/12/17/881

Thanks for the tip, but unfortunately this isn't possible on the
gpu_cfg_ahb_clk, as it is also needed for the Adreno IOMMU, which has
secure contexts that are set up from one of the bootloader stages and if
you reset/"mess up" one of them (by - in this case - un-clocking the
MMU), then the hypervisor will kick in and generate a fault, rebooting
the SoC.

Of course, this scenario is for the case in which you want to boot the
device without any gpucc nor any runtime pm user of that.. and the
aforementioned issue makes that solution not really usable.

Again, unfortunately.

Intresting, that's not true on all devices, but presumably you have
devices where it is.  Fun.