From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chris Wilson Subject: Re: [PATCH 02/15] drm/i915: Don't emit mbox updates without semaphores Date: Tue, 17 Dec 2013 19:24:41 +0000 Message-ID: <20131217192441.GU22448@nuc-i3427.alporthouse.com> References: <1387255851-24824-1-git-send-email-benjamin.widawsky@intel.com> <1387255851-24824-3-git-send-email-benjamin.widawsky@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from fireflyinternet.com (mail.fireflyinternet.com [87.106.93.118]) by gabe.freedesktop.org (Postfix) with ESMTP id BC112FCF1A for ; Tue, 17 Dec 2013 11:24:47 -0800 (PST) Content-Disposition: inline In-Reply-To: <1387255851-24824-3-git-send-email-benjamin.widawsky@intel.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: intel-gfx-bounces@lists.freedesktop.org Errors-To: intel-gfx-bounces@lists.freedesktop.org To: Ben Widawsky Cc: Intel GFX , Ben Widawsky List-Id: intel-gfx@lists.freedesktop.org On Mon, Dec 16, 2013 at 08:50:38PM -0800, Ben Widawsky wrote: > Aside from the fact that it leaves confusing dumps on error capture, it > is entirely unnecessary, and potentially harmful in cases like BDW, > where the instruction has changed. > > In reality (seemingly), this will have no behavioral impact. > > Signed-off-by: Ben Widawsky The reason why we currently do is because i915.semaphores can change at runtime. So we emit the instructions whilst i915.semaphores=0 just in case, it is enabled later. This restriction can be lifted with a little more work in handling the missed semaphores, I think, or it may just require a proof that everything is safe as is. -Chris -- Chris Wilson, Intel Open Source Technology Centre