Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759297AbcDEOIA (ORCPT ); Tue, 5 Apr 2016 10:08:00 -0400 Received: from mail-wm0-f51.google.com ([74.125.82.51]:32847 "EHLO mail-wm0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759282AbcDEOH5 (ORCPT ); Tue, 5 Apr 2016 10:07:57 -0400 MIME-Version: 1.0 In-Reply-To: References: <1459778134-30693-1-git-send-email-tomeu.vizoso@collabora.com> From: Tomeu Vizoso Date: Tue, 5 Apr 2016 16:07:36 +0200 X-Google-Sender-Auth: dhqzkR2oXGd2NpC51pcFWKkSbKI Message-ID: Subject: Re: [PATCH] drm/rockchip: Return -EBUSY if there's already a pending flip event v3 To: Daniel Stone Cc: "linux-arm-kernel@lists.infradead.org" , linux-rockchip , Linux Kernel Mailing List , dri-devel Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2312 Lines: 60 On 4 April 2016 at 17:44, Daniel Stone wrote: > Hi Tomeu, > > On 4 April 2016 at 14:55, Tomeu Vizoso wrote: >> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_fb.c b/drivers/gpu/drm/rockchip/rockchip_drm_fb.c >> index 3b8f652698f8..8305bbd2a4d7 100644 >> --- a/drivers/gpu/drm/rockchip/rockchip_drm_fb.c >> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_fb.c >> @@ -280,7 +280,18 @@ int rockchip_drm_atomic_commit(struct drm_device *dev, >> { >> struct rockchip_drm_private *private = dev->dev_private; >> struct rockchip_atomic_commit *commit = &private->commit; >> - int ret; >> + struct drm_crtc_state *crtc_state; >> + struct drm_crtc *crtc; >> + int i, ret; >> + >> + if (async) { >> + for_each_crtc_in_state(state, crtc, crtc_state, i) { >> + if (crtc->state->event || >> + rockchip_drm_crtc_has_pending_event(crtc)) { >> + return -EBUSY; >> + } >> + } >> + } > > Hmmm ... > > Doesn't this trigger before the VOP atomic_begin() helper, meaning > that anything with an event set will trigger the check? Seems like it > should be && rather than ||. So, these are the two cases that this code aims to handle: 1. A previous request with an event set hasn't progressed to atomic_begin yet, so the event field in drm_crtc_state (at this point, the old state) is still populated but vop->event still isn't. 2. A previous request has already progressed to atomic_begin but we haven't gotten yet the interrupt that signals its completion, so vop->event is populated but crtc->state->event isn't anymore. My understanding is that in both cases there's a pending flip event and we have to return -EBUSY if it's as async request. > Also, I know rockchip_drm_vop.c isn't holding dev->event_lock when it > checks vop->event, but it really should be ... and so should this > check. Otherwise you can race with the IRQ handler, which isn't > required to hold the CRTC lock. Cool, thanks. Tomeu > Cheers, > Daniel > _______________________________________________ > dri-devel mailing list > dri-devel@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/dri-devel