| Message ID | 20170621014457.26587-3-mario.kleiner.de@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 21/06/17 10:44 AM, Mario Kleiner wrote: > With instantaneous high precision vblank timestamping > that updates at leading edge of vblank, a cooked hw > vblank counter 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. > > Testing on Linux-4.12-rc5 + drm-next on a Radeon HD 5770 > (DCE 4) 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@gmail.com> > Cc: Alex Deucher <alexander.deucher@amd.com> > Cc: Michel Dänzer <michel.daenzer@amd.com> My only doubt is whether this is also reliable on older (e.g. pre-R600) GPUs. For newer GPUs (tested on Kaveri): Reviewed-and-Tested-by: Michel Dänzer <michel.daenzer@amd.com>
diff --git a/drivers/gpu/drm/radeon/radeon_irq_kms.c b/drivers/gpu/drm/radeon/radeon_irq_kms.c index 7aacb44..1860764 100644 --- a/drivers/gpu/drm/radeon/radeon_irq_kms.c +++ b/drivers/gpu/drm/radeon/radeon_irq_kms.c @@ -283,6 +283,10 @@ int radeon_irq_kms_init(struct radeon_device *rdev) int r = 0; spin_lock_init(&rdev->irq.lock); + + /* Disable vblank irqs aggressively for power-saving */ + rdev->ddev->vblank_disable_immediate = true; + r = drm_vblank_init(rdev->ddev, rdev->num_crtc); if (r) { return r;
With instantaneous high precision vblank timestamping that updates at leading edge of vblank, a cooked hw vblank counter 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. Testing on Linux-4.12-rc5 + drm-next on a Radeon HD 5770 (DCE 4) 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@gmail.com> Cc: Alex Deucher <alexander.deucher@amd.com> Cc: Michel Dänzer <michel.daenzer@amd.com> --- drivers/gpu/drm/radeon/radeon_irq_kms.c | 4 ++++ 1 file changed, 4 insertions(+)