From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.2 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DB8D2C04EBF for ; Tue, 16 Oct 2018 04:13:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 990AE20869 for ; Tue, 16 Oct 2018 04:13:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="vi3S7QeY" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 990AE20869 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728763AbeJPMCE (ORCPT ); Tue, 16 Oct 2018 08:02:04 -0400 Received: from mail.kernel.org ([198.145.29.99]:49616 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727259AbeJPMCD (ORCPT ); Tue, 16 Oct 2018 08:02:03 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id C8EA321480; Tue, 16 Oct 2018 04:13:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1539663220; bh=EgCur0T0J64rPQbrh2bomyCzMR+FQDkd7VEIWEwCvts=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=vi3S7QeYdmbvCVwOTboz45M2R4hZjk9qyEvVHd9TS7qmc44ISpOPG2CZxLVPSuCNU /q7eGMvAmrpLB/u/2cye11iQVhr74tomlXRrtuqZLXGxG69cjAXGQIWFhufAwqOryq uXyyHTs3fYU8y5u+YnCPwiswTYj9gZoN0VMefQmU= From: Sasha Levin To: stable@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Shirish S , Leo Li , Alex Deucher , Sasha Levin Subject: [PATCH AUTOSEL 4.18 082/100] drm/amd/display: Signal hw_done() after waiting for flip_done() Date: Tue, 16 Oct 2018 00:12:03 -0400 Message-Id: <20181016041221.135528-82-sashal@kernel.org> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20181016041221.135528-1-sashal@kernel.org> References: <20181016041221.135528-1-sashal@kernel.org> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Shirish S [ Upstream commit 987bf116445db5d63a5c2ed94c4479687d9c9973 ] In amdgpu_dm_commit_tail(), wait until flip_done() is signaled before we signal hw_done(). [Why] This is to temporarily address a paging error that occurs when a nonblocking commit contends with another commit, particularly in a mirrored display configuration where at least 2 CRTCs are updated. The error occurs in drm_atomic_helper_wait_for_flip_done(), when we attempt to access the contents of new_crtc_state->commit. Here's the sequence for a mirrored 2 display setup (irrelevant steps left out for clarity): **THREAD 1** | **THREAD 2** | Initialize atomic state for flip | | Queue worker | ... | Do work for flip | | Signal hw_done() on CRTC 1 | Signal hw_done() on CRTC 2 | | Wait for flip_done() on CRTC 1 <---- **PREEMPTED BY THREAD 1** Initialize atomic state for cursor | update (1) | | Do cursor update work on both CRTCs | | Clear atomic state (2) | **DONE** | ... | | Wait for flip_done() on CRTC 2 | *ERROR* | The issue starts with (1). When the atomic state is initialized, the current CRTC states are duplicated to be the new_crtc_states, and referenced to be the old_crtc_states. (The new_crtc_states are to be filled with update data.) Some things to note: * Due to the mirrored configuration, the cursor updates on both CRTCs. * At this point, the pflip IRQ has already been handled, and flip_done signaled on all CRTCs. The cursor commit can therefore continue. * The old_crtc_states used by the cursor update are the **same states** as the new_crtc_states used by the flip worker. At (2), the old_crtc_state is freed (*), and the cursor commit completes. We then context switch back to the flip worker, where we attempt to access the new_crtc_state->commit object. This is problematic, as this state has already been freed. (*) Technically, 'state->crtcs[i].state' is freed, which was made to reference old_crtc_state in drm_atomic_helper_swap_state() [How] By moving hw_done() after wait_for_flip_done(), we're guaranteed that the new_crtc_state (from the flip worker's perspective) still exists. This is because any other commit will be blocked, waiting for the hw_done() signal. Note that both the i915 and imx drivers have this sequence flipped already, masking this problem. Signed-off-by: Shirish S Signed-off-by: Leo Li Reviewed-by: Harry Wentland Signed-off-by: Alex Deucher Signed-off-by: Sasha Levin --- drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c index e484d0a94bdc..5b9cc3aeaa55 100644 --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c @@ -4494,12 +4494,18 @@ static void amdgpu_dm_atomic_commit_tail(struct drm_atomic_state *state) } spin_unlock_irqrestore(&adev->ddev->event_lock, flags); - /* Signal HW programming completion */ - drm_atomic_helper_commit_hw_done(state); if (wait_for_vblank) drm_atomic_helper_wait_for_flip_done(dev, state); + /* + * FIXME: + * Delay hw_done() until flip_done() is signaled. This is to block + * another commit from freeing the CRTC state while we're still + * waiting on flip_done. + */ + drm_atomic_helper_commit_hw_done(state); + drm_atomic_helper_cleanup_planes(dev, state); /* Finally, drop a runtime PM reference for each newly disabled CRTC, -- 2.17.1