From: Mario Kleiner <mario.kleiner.de@gmail.com>
Date: Thu, 22 Jun 2017 03:28:11 +0200
Subject: drm/vc4: Allow vblank_disable_immediate on non-fw-kms. (v2)
Git-commit: 7d2818f54e38e40232c65866b58c8b627dbf5711
Patch-mainline: v4.14-rc1
References: FATE#326289 FATE#326079 FATE#326049 FATE#322398 FATE#326166

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
vblank irq disable/enable.

Testing against rpi-4.12-rc5 Linux kernel 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
would keep vblank irqs on to approximate old behavior.

v2: Respin onto drm-misc-next, per Eric's suggestion.
    Drop !vc4->firmware_kms check, as the firmware_kms
    implementation does not exist in upstream.

Signed-off-by: Mario Kleiner <mario.kleiner.de@gmail.com>
Cc: Eric Anholt <eric@anholt.net>
Reviewed-by: Eric Anholt <eric@anholt.net>
Link: http://patchwork.freedesktop.org/patch/msgid/20170622012811.2139-1-mario.kleiner.de@gmail.com

Acked-by: Petr Tesarik <ptesarik@suse.com>
---
 drivers/gpu/drm/vc4/vc4_kms.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/gpu/drm/vc4/vc4_kms.c
+++ b/drivers/gpu/drm/vc4/vc4_kms.c
@@ -241,6 +241,9 @@ int vc4_kms_load(struct drm_device *dev)
 
 	sema_init(&vc4->async_modeset, 1);
 
+	/* Set support for vblank irq fast disable, before drm_vblank_init() */
+	dev->vblank_disable_immediate = true;
+
 	ret = drm_vblank_init(dev, dev->mode_config.num_crtc);
 	if (ret < 0) {
 		dev_err(dev->dev, "failed to initialize vblank\n");