Some users have reported hard system hangs on the Raspberry Pi 4 (V3D 4.2)
under GPU load [1][2][3]. Investigation had traced these to V3D caches and
MMU being left in an inconsistent state across PM transitions. This series
addresses three distinct issues in the cache and MMU maintenance:
1. PATCH 1: Addresses an issue on pre-V3D 7.1 hardware, in which
starting a clean while an L2T flush is still pending can clobber bits
in L2TCACTL and leave the caches inconsistent. This issue existed
before the runtime PM series.
2. PATCH 2: Fixes the MMU TLB/cache flush in v3d_mmu_set_page_table()
being silently skipped during runtime resume. Directly addresses
the system hangs reported by the users.
3. PATCH 3: Cleans the V3D caches on runtime suspend, so all dirty lines
are written back to memory before the power domain is shut down.
Directly addresses the error `v3d fec00000.v3d: MMU error from
client L2T (7) at 0xff877600, pte invalid` reported during the
hangs.
Together these restore correct cache/MMU coherency around runtime PM,
addressing the reported hangs. Moreover, with this fixes, it was possible
to reduce the autosuspend delay, which was increased as the shorter delays
used to cause more frequent runtime suspend/resume cycles, which exposed
the cache and MMU coherency bugs as random GPU hangs. With those fixed,
we can reduce the autosuspend delay to a more reasonable value.
[1] https://github.com/raspberrypi/linux/issues/7381
[2] https://github.com/raspberrypi/linux/issues/7396
[3] https://github.com/raspberrypi/linux/issues/7397
Best regards,
- Maíra
---
Maíra Canal (4):
drm/v3d: Wait for pending L2T flush before cleaning caches
drm/v3d: Flush MMU TLB and cache during runtime resume
drm/v3d: Clean caches before runtime suspend
drm/v3d: Reduce PM runtime autosuspend delay
drivers/gpu/drm/v3d/v3d_drv.c | 2 +-
drivers/gpu/drm/v3d/v3d_gem.c | 8 ++++++++
drivers/gpu/drm/v3d/v3d_mmu.c | 31 ++++++++++++++++++++++---------
drivers/gpu/drm/v3d/v3d_power.c | 2 ++
4 files changed, 33 insertions(+), 10 deletions(-)
---
base-commit: 61de054a772a1feda6364931ab1baf9038abf1c8
change-id: 20260528-v3d-fix-rpi4-freezes-8bae519d04ce
