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

[Mario Kleiner <mario.kleiner.de@gmail.com>]

On 05/29/2015 07:19 PM, Daniel Vetter wrote:
> 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
>

I think the nv_crtc_prepare() path modified in your first hunk is only 
for the original nv04 display engine for very old cards. nv50+ 
(GeForce-8 and later) take different paths.

-mario
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