Re: [PATCH v2 05/11] clk: qcom: gcc-msm8998: Mark gpu_cfg_ahb_clk as critical

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Il 14/01/21 23:37, Jeffrey Hugo ha scritto:
On Thu, Jan 14, 2021 at 3:13 PM AngeloGioacchino Del Regno
<angelogioacchino.delregno@xxxxxxxxxxxxxx> wrote:

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.



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