With instantaneous high precision vblank timestamping that updates at leading edge of vblank, the emulated "hw vblank counter" from vblank timestamping, which increments at leading edge of vblank, and reliable page flip execution and completion at leading edge of vblank, we should meet the requirements for fast/ immediate vblank irq disable/enable. This is only allowed on nv50+ gpu's, ie. the ones with atomic modesetting. One requirement for immediate vblank disable is that high precision vblank timestamping works reliably all the time on all connectors. This is not the case on all pre-nv50 parts for analog VGA outputs, where we currently don't always have support for scanout position queries and therefore fall back to vblank interrupt timestamping. The implementation in nv04_head_state() does not return valid values for vblanks, vtotal, hblanks, htotal for VGA outputs on all cards, but those are needed for scanout position queries. Testing on Linux-4.12-rc5 + drm-next on a GeForce 9500 GT (NV G96) with timing measurement equipment indicates this works fine, so allow immediate vblank disable for power saving. For debugging in case of unexpected trouble, booting with kernel cmdline option drm.vblankoffdelay=0 (or echo 0 > /sys/module/drm/parameters/vblankoffdelay) would keep vblank irqs permanently on to approximate old behavior. Signed-off-by: Mario Kleiner <mario.kleiner.de at gmail.com> Cc: Ben Skeggs <bskeggs at redhat.com> --- drivers/gpu/drm/nouveau/nv50_display.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/gpu/drm/nouveau/nv50_display.c b/drivers/gpu/drm/nouveau/nv50_display.c index e3132a2..f2f2a7c 100644 --- a/drivers/gpu/drm/nouveau/nv50_display.c +++ b/drivers/gpu/drm/nouveau/nv50_display.c @@ -4495,6 +4495,9 @@ nv50_display_create(struct drm_device *dev) connector->funcs->destroy(connector); } + /* Disable vblank irqs aggressively for power-saving, safe on nv50+ */ + dev->vblank_disable_immediate = true; + out: if (ret) nv50_display_destroy(dev); -- 2.7.4
