From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jani Nikula Subject: Re: [PATCH v4] drm/i915: use hrtimer in wait for vblank Date: Tue, 25 Mar 2014 11:32:23 +0200 Message-ID: <87eh1qvd20.fsf@intel.com> References: <1395737902-11984-1-git-send-email-arun.r.murthy@intel.com> <20140325090703.GY4366@nuc-i3427.alporthouse.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mga02.intel.com (mga02.intel.com [134.134.136.20]) by gabe.freedesktop.org (Postfix) with ESMTP id 05D2E6E0BA for ; Tue, 25 Mar 2014 02:32:27 -0700 (PDT) In-Reply-To: <20140325090703.GY4366@nuc-i3427.alporthouse.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" To: Chris Wilson , Arun R Murthy Cc: airlied@linux.ie, daniel.vetter@ffwll.ch, intel-gfx@lists.freedesktop.org List-Id: intel-gfx@lists.freedesktop.org On Tue, 25 Mar 2014, Chris Wilson wrote: > On Tue, Mar 25, 2014 at 02:28:22PM +0530, Arun R Murthy wrote: >> In wait for vblank use usleep_range, which will use hrtimers instead of >> msleep. Using msleep(1~20) there are more chances of sleeping for 20ms. >> Using usleep_range uses hrtimers and hence are precise, worst case will >> trigger an interrupt at the higher/max timeout. >> >> As per kernel document "Documentation/timers/timers-howto.txt" sleeping >> for 10us to 20ms its recomended to use usleep_range. >> >> Signed-off-by: Arun R Murthy > > Lgtm, I still feel that our use of W=1 is fairly arbitrary and worth > tweaking in future. With the current code, this is essentially the same as the original patch. We never have W > 20, and thus we always take the usleep_range() path. So W is definitely worth tweaking if we go with this now. Nitpick, the macro params should be parenthesized. This will now break for _wait_for(cond, 10, 2 + 1) and such. Arun, please don't immediately reply with updated patches if there's discussion still going on. See what the conclusion is first. Thanks. BR, Jani. > > Reviewed-by: Chris Wilson > -Chris > > -- > Chris Wilson, Intel Open Source Technology Centre -- Jani Nikula, Intel Open Source Technology Center