On Thu, Jan 14, 2021 at 4:05 PM AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxxx> wrote: > > 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. Intresting, that's not true on all devices, but presumably you have devices where it is. Fun.
