Re: [PATCH 1/3] drm/nouveau: Use drm_vblank_on/off consistently

Daniel Vetter
2015-05-29T17:16:54Z

On Fri, May 29, 2015 at 06:50:06PM +0200, Mario Kleiner wrote:
> On 05/27/2015 11:04 AM, Daniel Vetter wrote:
> >In
> >
> >commit 9cba5efab5a8145ae6c52ea273553f069c294482
> >Author: Mario Kleiner <mario.kleiner.de@gmail.com>
> >Date: Tue Jul 29 02:36:44 2014 +0200
> >
> > drm/nouveau: Dis/Enable vblank irqs during suspend/resume
> >
> >drm_vblank_on/off calls where added around suspend/resume to make sure
> >vblank stay doesn't go boom over that transition. But nouveau already
> >used drm_vblank_pre/post_modeset over modesets. Instead use
> >drm_vblank_on/off everyhwere. The slight change here is that after
> >_off drm_vblank_get will refuse to work right away, but nouveau
> >doesn't seem to depend upon that anywhere outside of the pageflip
> >paths.
> >
> >The longer-term plan here is to switch all kms drivers to
> >drm_vblank_on/off so that common code like pending event cleanup can
> >be done there, while drm_vblank_pre/post_modeset will be purely
> >drm internal for the old UMS ioctl.
> >
> >Note that the drm_vblank_off still seems required in the suspend path
> >since nouveau doesn't explicitly disable crtcs. But on the resume side
> >drm_helper_resume_force_mode should end up calling drm_vblank_on
> >through the nouveau crtc hooks already. Hence remove the call in the
> >resume code.
> >
> >Cc: Mario Kleiner <mario.kleiner.de@gmail.com>
> >Cc: Ben Skeggs <bskeggs@redhat.com>
> >Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> >---
> > drivers/gpu/drm/nouveau/dispnv04/crtc.c | 4 ++--
> > drivers/gpu/drm/nouveau/nouveau_display.c | 4 ----
> > 2 files changed, 2 insertions(+), 6 deletions(-)
> >
> >diff --git a/drivers/gpu/drm/nouveau/dispnv04/crtc.c b/drivers/gpu/drm/nouveau/dispnv04/crtc.c
> >index 3d96b49fe662..dab24066fa21 100644
> >--- a/drivers/gpu/drm/nouveau/dispnv04/crtc.c
> >+++ b/drivers/gpu/drm/nouveau/dispnv04/crtc.c
> >@@ -708,7 +708,7 @@ static void nv_crtc_prepare(struct drm_crtc *crtc)
> > if (nv_two_heads(dev))
> > NVSetOwner(dev, nv_crtc->index);
> >
> >- drm_vblank_pre_modeset(dev, nv_crtc->index);
> >+ drm_vblank_off(dev, nv_crtc->index);
> > funcs->dpms(crtc, DRM_MODE_DPMS_OFF);
> >
> > NVBlankScreen(dev, nv_crtc->index, true);
> >@@ -740,7 +740,7 @@ static void nv_crtc_commit(struct drm_crtc *crtc)
> > #endif
> >
> > funcs->dpms(crtc, DRM_MODE_DPMS_ON);
> >- drm_vblank_post_modeset(dev, nv_crtc->index);
> >+ drm_vblank_on(dev, nv_crtc->index);
> > }
>
> The above hunk is probably correct, but i couldn't test it without
> sufficiently old pre-nv 50 hardware.
>
> >
> > static void nv_crtc_destroy(struct drm_crtc *crtc)
> >diff --git a/drivers/gpu/drm/nouveau/nouveau_display.c b/drivers/gpu/drm/nouveau/nouveau_display.c
> >index 8670d90cdc11..d824023f9fc6 100644
> >--- a/drivers/gpu/drm/nouveau/nouveau_display.c
> >+++ b/drivers/gpu/drm/nouveau/nouveau_display.c
> >@@ -620,10 +620,6 @@ nouveau_display_resume(struct drm_device *dev, bool runtime)
> > nv_crtc->lut.depth = 0;
> > }
> >
> >- /* Make sure that drm and hw vblank irqs get resumed if needed. */
> >- for (head = 0; head < dev->mode_config.num_crtc; head++)
> >- drm_vblank_on(dev, head);
> >-
> > /* This should ensure we don't hit a locking problem when someone
> > * wakes us up via a connector. We should never go into suspend
> > * while the display is on anyways.
> >
>
> Tested this one and this hunk breaks suspend/resume. After a suspend/resume
> cycle, all OpenGL apps and composited desktop are dead, as the core can't
> get any vblank irq's enabled anymore.
>
> So the drm_vblank_on() is still needed here.

Hm that's very surprising. As mentioned above the force_mode_restore
should be calling nv_crtc_prepare already and fix this all up for us. I
guess I need to dig out my nv card and trace what's really going on here.

Enabling interrupts when the crtc is off isn't a good idea.
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation