From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f66.google.com ([74.125.82.66]:33417 "EHLO mail-wm0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756464AbcBIN1s (ORCPT ); Tue, 9 Feb 2016 08:27:48 -0500 Received: by mail-wm0-f66.google.com with SMTP id c200so3434314wme.0 for ; Tue, 09 Feb 2016 05:27:48 -0800 (PST) Subject: Re: [PATCH 1/6] drm: No-Op redundant calls to drm_vblank_off() To: Daniel Vetter References: <1454894009-15466-1-git-send-email-mario.kleiner.de@gmail.com> <1454894009-15466-2-git-send-email-mario.kleiner.de@gmail.com> <20160209095455.GL11240@phenom.ffwll.local> Cc: dri-devel@lists.freedesktop.org, linux@bernd-steinhauser.de, stable@vger.kernel.org, michel@daenzer.net, vbabka@suse.cz, ville.syrjala@linux.intel.com, daniel.vetter@ffwll.ch, alexander.deucher@amd.com, christian.koenig@amd.com From: Mario Kleiner Message-ID: <56B9E950.9020004@gmail.com> Date: Tue, 9 Feb 2016 14:27:44 +0100 MIME-Version: 1.0 In-Reply-To: <20160209095455.GL11240@phenom.ffwll.local> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: stable-owner@vger.kernel.org List-ID: On 02/09/2016 10:54 AM, Daniel Vetter wrote: > On Mon, Feb 08, 2016 at 02:13:24AM +0100, Mario Kleiner wrote: >> Otherwise if a kms driver calls into drm_vblank_off() more than once >> before calling drm_vblank_on() again, the redundant calls to >> vblank_disable_and_save() will call drm_update_vblank_count() >> while hw vblank counters and vblank timestamping are in a undefined >> state during modesets, dpms off etc. >> >> At least with the legacy drm helpers it is not unusual to >> get multiple calls to drm_vblank_off and drm_vblank_on, e.g., >> half a dozen calls to drm_vblank_off and two calls to drm_vblank_on >> were observed on radeon-kms during dpms-off -> dpms-on transition. >> >> Fixes large jumps of the software maintained vblank counter due to >> the hardware vblank counter resetting to zero during dpms off or >> modeset, e.g., if radeon-kms is modified to use drm_vblank_off/on >> instead of drm_vblank_pre/post_modeset(). >> >> This fixes a regression caused by the changes made to >> drm_update_vblank_count() in Linux 4.4. >> >> Signed-off-by: Mario Kleiner >> Cc: # 4.4+ >> Cc: michel@daenzer.net >> Cc: vbabka@suse.cz >> Cc: ville.syrjala@linux.intel.com >> Cc: daniel.vetter@ffwll.ch >> Cc: dri-devel@lists.freedesktop.org >> Cc: alexander.deucher@amd.com >> Cc: christian.koenig@amd.com >> --- >> drivers/gpu/drm/drm_irq.c | 11 ++++++++++- >> 1 file changed, 10 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c >> index 607f493..bcb8528 100644 >> --- a/drivers/gpu/drm/drm_irq.c >> +++ b/drivers/gpu/drm/drm_irq.c >> @@ -1313,7 +1313,13 @@ void drm_vblank_off(struct drm_device *dev, unsigned int pipe) >> spin_lock_irqsave(&dev->event_lock, irqflags); >> >> spin_lock(&dev->vbl_lock); >> - vblank_disable_and_save(dev, pipe); >> + DRM_DEBUG_VBL("crtc %d, vblank enabled %d, inmodeset %d\n", >> + pipe, vblank->enabled, vblank->inmodeset); >> + >> + /* Avoid redundant vblank disables without previous drm_vblank_on(). */ >> + if (!vblank->inmodeset) > > Since atomic drivers shouldn't suck so badly at this, maybe > > if (DRIVER_ATOMIC || !vblank->inmodeset) > > instead? That way the flexibility would be constraint to old drivers that > need it because legacy crtc helpers suck. With that change: > > Reviewed-by: Daniel Vetter > Ok, thanks, will change that. -mario >> + vblank_disable_and_save(dev, pipe); >> + >> wake_up(&vblank->queue); >> >> /* >> @@ -1415,6 +1421,9 @@ void drm_vblank_on(struct drm_device *dev, unsigned int pipe) >> return; >> >> spin_lock_irqsave(&dev->vbl_lock, irqflags); >> + DRM_DEBUG_VBL("crtc %d, vblank enabled %d, inmodeset %d\n", >> + pipe, vblank->enabled, vblank->inmodeset); >> + >> /* Drop our private "prevent drm_vblank_get" refcount */ >> if (vblank->inmodeset) { >> atomic_dec(&vblank->refcount); >> -- >> 1.9.1 >> >