On Wed, Sep 9, 2026 at 5:32 AM Neil Armstrong <[email protected]> wrote: > > On 9/9/26 11:06, Konrad Dybcio wrote: > > On 9/8/26 3:24 PM, Neil Armstrong wrote: > >> The a750 uses the CX AO Counters instead of the GMU_ALWAYS_ON_COUNTER > >> register on A6xx and other A7xx GPUs, use it when running a A750 GPU. > >> > >> Signed-off-by: Neil Armstrong <[email protected]> > >> --- > >> drivers/gpu/drm/msm/adreno/a6xx_gpu.c | 12 +++++++++--- > >> 1 file changed, 9 insertions(+), 3 deletions(-) > >> > >> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c > >> b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c > >> index f9de9329dee3..081e79ea4652 100644 > >> --- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c > >> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c > >> @@ -23,9 +23,15 @@ static u64 a6xx_gmu_get_timestamp(struct msm_gpu *gpu) > >> u64 count_hi, count_lo, temp; > >> > >> do { > >> - count_hi = gmu_read(&a6xx_gpu->gmu, > >> REG_A6XX_GMU_ALWAYS_ON_COUNTER_H); > >> - count_lo = gmu_read(&a6xx_gpu->gmu, > >> REG_A6XX_GMU_ALWAYS_ON_COUNTER_L); > >> - temp = gmu_read(&a6xx_gpu->gmu, > >> REG_A6XX_GMU_ALWAYS_ON_COUNTER_H); > >> + if (adreno_is_a750_family(adreno_gpu)) { > >> + count_hi = gmu_read(&a6xx_gpu->gmu, > >> REG_A7XX_GMU_CX_AO_COUNTER_H); > >> + count_lo = gmu_read(&a6xx_gpu->gmu, > >> REG_A7XX_GMU_CX_AO_COUNTER_L); > >> + temp = gmu_read(&a6xx_gpu->gmu, > >> REG_A7XX_GMU_CX_AO_COUNTER_H); > > > > KGSL apparently *writes* the system time to these registers, is that > > an idiosyncrasy regarding how the vendor userland drivers then use > > this counter? > > This is a GMU counter, no sure why & how KGSL or freedreno would write > anything to it...
It is writeable. This is part of implementing VK_KHR_calibrated_timestamps. The idea is that when the GPU suspends and resumes, we keep track of how many ticks it would've taken and then pretend to advance the counter by writing the CX counter (after powering on CX but before powering on GX which initializes the normal GMU counter). Note that VK_KHR_calibrated_timestamps worked initially on turnip but the tests started failing with v6.19. I haven't bisected yet but my guess is CX was never actually collapsing for whatever reason and we made it collapse hence breaking the tests. So we probably do need this. Connor > > > > > Konrad > > > > P.S. looks like a8xx also has this counter > > >
