On Thursday, 4 December 2025 21:21:08 Central European Standard Time Chia-I Wu wrote: > On Wed, Dec 3, 2025 at 6:04 AM Nicolas Frattaroli > <[email protected]> wrote: > > > > Mali GPUs have three registers that indicate which parts of the hardware > > are powered and active at any moment. These take the form of bitmaps. In > > the case of SHADER_PWRACTIVE for example, a high bit indicates that the > > shader core corresponding to that bit index is active. These bitmaps > > aren't solely contiguous bits, as it's common to have holes in the > > sequence of shader core indices, and the actual set of which cores are > > present is defined by the "shader present" register. > > > > When the GPU finishes a power state transition, it fires a > > GPU_IRQ_POWER_CHANGED_ALL interrupt. After such an interrupt is > > received, the PWRACTIVE registers will likely contain interesting new > > information. > I am seeing > > irq/342-panthor-412 [000] ..... 934.526754: gpu_power_active: > shader_bitmap=0x0 tiler_bitmap=0x0 l2_bitmap=0x0 > irq/342-panthor-412 [000] ..... 936.640356: gpu_power_active: > shader_bitmap=0x0 tiler_bitmap=0x0 l2_bitmap=0x0 > > on a gpu-bound test. It does not look like collecting samples on > GPU_IRQ_POWER_CHANGED_ALL gives too much info.
On what GPU and SoC is that? If it's MT8196 then I wouldn't be surprised if it just broke that hardware register, considering what it did to the SHADER_PRESENT register. On RK3588 (v10), GPU_IRQ_POWER_CHANGED_ALL reliably fires when there is new information available in those registers. I haven't tried on MT8196 (v13) yet because that still doesn't boot with mainline so testing anything is a pain. I don't have any v12 or v11 hardware to test with. From what I understand, there's no open enough platform to do v11 testing on, just the Pixel 8 and Pixel 9. I could look into the Cix SoC for v12 though some day, but I don't own one at the moment. > > I think they are more useful to be collected periodically, such that > we know that in the past X seconds, Y out of a total of Z samples > indicates activities. That's best done in userspace, and panthor's > role should be to provide an uapi such as > https://lore.kernel.org/all/[email protected]/. This wouldn't give you information on the time a power transition has completed, which is one of the motivations. A periodically collected PWRACTIVE would just be roughly correlated to how busy the GPU is, which isn't very useful additional information as the performance counters themselves are likely a better source of that kind of info. What I need to do is restrict this to <= v13 in the next revision however, because v14 reworks this stuff. Kind regards, Nicolas Frattaroli
