From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933097AbbLCKAu (ORCPT ); Thu, 3 Dec 2015 05:00:50 -0500 Received: from foss.arm.com ([217.140.101.70]:47765 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932799AbbLCKAY (ORCPT ); Thu, 3 Dec 2015 05:00:24 -0500 Date: Thu, 3 Dec 2015 10:00:21 +0000 From: Liviu Dudau To: Daniel Stone Cc: David Airlie , Catalin Marinas , Will Deacon , Rob Herring , Sudeep Holla , Jon Medhurst , Mark Rutland , Ian Campbell , Kumar Gala , Rob Herring , Russell King , devicetree , Pawel Moll , Arnd Bergmann , Greg Kroah-Hartman , Punit Agrawal , LKML , DRI devel , Andrew Morton , Robin Murphy , LAKML Subject: Re: [PATCH v3 2/4] drm: Add support for ARM's HDLCD controller. Message-ID: <20151203100021.GD972@e106497-lin.cambridge.arm.com> References: <1449058982-18595-1-git-send-email-Liviu.Dudau@arm.com> <1449058982-18595-3-git-send-email-Liviu.Dudau@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Dec 02, 2015 at 05:21:44PM +0000, Daniel Stone wrote: > Hi Liviu, Hi Daniel, > > On 2 December 2015 at 12:23, Liviu Dudau wrote: > > + if (irq_status & HDLCD_INTERRUPT_VSYNC) { > > + unsigned long flags; > > + > > + drm_handle_vblank(drm, 0); > > + > > + spin_lock_irqsave(&drm->event_lock, flags); > > + if (hdlcd->event) { > > + drm_send_vblank_event(drm, hdlcd->event->pipe, hdlcd->event); > > + drm_crtc_vblank_put(&hdlcd->crtc); > > + hdlcd->event = NULL; > > + } > > + spin_unlock_irqrestore(&drm->event_lock, flags); > > + } > > As with VC4 and Rockchip, you're missing a ->preclose handler in your > drm_drv, to make sure that you don't try to send events to a dead > client (which causes an OOPS): > https://git.collabora.com/cgit/user/daniels/linux.git/commit/?h=wip/4.4.x/rockchip-drm-fixes&id=d14f21bcd7 > (and its parent) Thanks for reviewing this! I do acknowledge your concerns and you might correct my understanding on how atomic DRM works, but I believe in this case we should be safe. The event stored in hdlcd->event is taken out of the crtc->state->event during the crtc->atomic_begin() callback. If the client is dead the callback should not be called, so that's how we avoid the OOPS. > Also, is there anything preventing clients from submitting multiple > pageflips before the event is sent? I couldn't see anything from a > quick look, so you could have the situation of: > - client submits pageflip, event 1 stored to hdlcd->event > - client submits pageflip, event 2 stored to hdlcd->event > - vblank arrives, event 2 is sent > - event 1 has disappeared and been leaked As for multiple events being submitted before vsync interrupt happening: given that the event is plucked out of the crtc->state, is that possible? And if so, is there a case where having the later event overwrite the earlier one a desired outcome? > > Cheers, > Daniel > Best regards, Liviu -- ==================== | I would like to | | fix the world, | | but they're not | | giving me the | \ source code! / --------------- ¯\_(ツ)_/¯