When the fence list is empty, host1x_intr_update_hw_state() falls through to host1x_intr_disable_syncpt_intr() which does two MMIO writes to disable the syncpoint interrupt and clear its status.
The ISR has already disabled and acked the interrupt before calling host1x_intr_handle_interrupt(), making these two writes redundant. Skip the update_hw_state() call if no fences remain. Measured Syncpoint wait latency (50000 samples): Average latency: 10.6 us -> 9.4 us 99.99 pct latency: 51.90 us -> 36.58 us Signed-off-by: Tanmay Patil <[email protected]> --- drivers/gpu/host1x/intr.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/host1x/intr.c b/drivers/gpu/host1x/intr.c index f77a678949e9..723297250768 100644 --- a/drivers/gpu/host1x/intr.c +++ b/drivers/gpu/host1x/intr.c @@ -92,8 +92,12 @@ void host1x_intr_handle_interrupt(struct host1x *host, unsigned int id) host1x_fence_signal(fence); } - /* Re-enable interrupt if necessary */ - host1x_intr_update_hw_state(host, sp); + /* + * Re-enable interrupt if necessary. The ISR already disabled the interrupt, + * so if no fences remain, no update is needed. + */ + if (!list_empty(&sp->fences.list)) + host1x_intr_update_hw_state(host, sp); spin_unlock(&sp->fences.lock); } -- 2.54.0
