On Wed, 22 Dec 2010 05:36:13 +0100 Mario Kleiner mario.kleiner@tuebingen.mpg.de wrote:
Message: 1 Date: Mon, 20 Dec 2010 19:23:40 -0800 From: Keith Packard keithp@keithp.com Subject: Re: [Intel-gfx] [PATCH] drm: Aggressively disable vblanks To: Andy Lutomirski luto@MIT.EDU, Jesse Barnes jbarnes@virtuousgeek.org, Chris Wilson chris@chris-wilson.co.uk, David Airlie airlied@linux.ie Cc: intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org Message-ID: yunfwtrrepv.fsf@aiko.keithp.com Content-Type: text/plain; charset="us-ascii"
On Mon, 20 Dec 2010 14:00:54 -0500, Andy Lutomirski luto@MIT.EDU wrote:
Enabling and disabling the vblank interrupt (on devices that support it) is cheap. So disable it quickly after each interrupt.
So, the concern (and reason for the original design) was that you might lose count of vblank interrupts as vblanks are counted differently while off than while on. If vblank interrupts get enabled near the interrupt time, is it possible that you'll end up off by one somehow?
Leaving them enabled for 'a while' was supposed to reduce the impact of this potential error.
-- keith.packard@intel.com