From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jesse Barnes Subject: Re: [PATCH 4/6] drm/i915: Disable FBC across page-flipping Date: Thu, 7 Jul 2011 09:15:58 -0700 Message-ID: <20110707091558.0b1963cd@jbarnes-desktop> References: <1310039291-22554-1-git-send-email-chris@chris-wilson.co.uk> <1310039291-22554-5-git-send-email-chris@chris-wilson.co.uk> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from oproxy3-pub.bluehost.com (oproxy3-pub.bluehost.com [69.89.21.8]) by gabe.freedesktop.org (Postfix) with SMTP id 5585E9E709 for ; Thu, 7 Jul 2011 09:16:12 -0700 (PDT) In-Reply-To: <1310039291-22554-5-git-send-email-chris@chris-wilson.co.uk> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: intel-gfx-bounces+gcfxdi-intel-gfx=m.gmane.org@lists.freedesktop.org Errors-To: intel-gfx-bounces+gcfxdi-intel-gfx=m.gmane.org@lists.freedesktop.org To: Chris Wilson Cc: intel-gfx@lists.freedesktop.org List-Id: intel-gfx@lists.freedesktop.org On Thu, 7 Jul 2011 12:48:09 +0100 Chris Wilson wrote: > Page-flipping updates the scanout address, nukes the FBC compressed > image and so forces an FBC update so that the displayed image remains > consistent. However, page-flipping does not update the FBC registers > themselves, which remain pointing to both the old address and the old > CPU fence. Future updates to the new front-buffer (scanout) are then > undetected! > > This first approach to demonstrate the issue and highlight the fix, > simply disables FBC upon page-flip (a recompression will be forced on > every flip so FBC becomes immaterial) and then re-enables FBC in the > page-flip finish work function, so that the FBC registers are now > pointing to the new framebuffer and front-buffer rendering works once > more. > > Ideally, we want to only re-enable FBC after page-flipping is complete, > as otherwise we are just wasting cycles (along with an undesirable > wait-for-vblank which will halve the frame-rate of vsync'ed games) and > power (with needless recompression) whilst the page-flipping application > is still running. > > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=33487 > Signed-off-by: Chris Wilson > --- Yeah just disabling it is probably better than trying to let the hw figure out what to recompress since it likely won't be worthwhile. Reviewed-by: Jesse Barnes -- Jesse Barnes, Intel Open Source Technology Center