Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider: - [High] drm/panfrost: inverted hardware disable sequence risks spurious dump --
commit 3efe7a19ba3bb185c762f241fc91b732bd783ed3 Author: Adrián Larumbe <[email protected]> drm/panfrost: Move perfcnt GPU disable sequence into a helper This commit introduces a helper function to avoid repetition of the hardware performance counter disable sequence. > diff --git a/drivers/gpu/drm/panfrost/panfrost_perfcnt.c > b/drivers/gpu/drm/panfrost/panfrost_perfcnt.c > index 7020c0192e189..f71534e741b65 100644 > --- a/drivers/gpu/drm/panfrost/panfrost_perfcnt.c > +++ b/drivers/gpu/drm/panfrost/panfrost_perfcnt.c > @@ -35,6 +35,16 @@ struct panfrost_perfcnt { > struct completion dump_comp; > }; > > +static void panfrost_perfcnt_hw_disable(struct panfrost_device *pfdev) > +{ > + gpu_write(pfdev, GPU_PERFCNT_CFG, > + GPU_PERFCNT_CFG_MODE(GPU_PERFCNT_CFG_MODE_OFF)); > + gpu_write(pfdev, GPU_PRFCNT_JM_EN, 0x0); > + gpu_write(pfdev, GPU_PRFCNT_SHADER_EN, 0x0); > + gpu_write(pfdev, GPU_PRFCNT_MMU_L2_EN, 0x0); > + gpu_write(pfdev, GPU_PRFCNT_TILER_EN, 0); > +} [Severity: High] Does this sequence introduce a risk of a spurious hardware dump? The new helper turns off the GPU_PERFCNT_CFG register before disabling the individual block counters, which reverses the previous safe sequence in panfrost_perfcnt_disable_locked() where the EN registers were cleared first. Modifying the CFG register while TILER_EN is still active might trigger a spurious dump. This seems similar to hardware erratum PRLAM-8186, which requires TILER_EN to be off before modifying the CFG register to enable counters. [ ... ] > @@ -193,12 +203,7 @@ static int panfrost_perfcnt_disable_locked(struct > panfrost_device *pfdev, > if (user != perfcnt->user) > return -EINVAL; > > - gpu_write(pfdev, GPU_PRFCNT_JM_EN, 0x0); > - gpu_write(pfdev, GPU_PRFCNT_SHADER_EN, 0x0); > - gpu_write(pfdev, GPU_PRFCNT_MMU_L2_EN, 0x0); > - gpu_write(pfdev, GPU_PRFCNT_TILER_EN, 0); > - gpu_write(pfdev, GPU_PERFCNT_CFG, > - GPU_PERFCNT_CFG_MODE(GPU_PERFCNT_CFG_MODE_OFF)); > + panfrost_perfcnt_hw_disable(pfdev); > > perfcnt->user = NULL; > drm_gem_vunmap(&perfcnt->mapping->obj->base.base, &map); [Severity: High] Could a spurious hardware dump here result in memory corruption? Because the inverted hardware disable sequence is invoked while TILER_EN is active, a spurious hardware dump would cause the GPU to write to the performance counter buffer asynchronously. Since panfrost_perfcnt_disable_locked() immediately tears down and unmaps this memory via drm_gem_vunmap(), could the GPU perform a DMA write-after-free, leading to an IOMMU fault or memory corruption? -- Sashiko AI review · https://sashiko.dev/#/patchset/[email protected]?part=11
