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=-9.8 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 32044C433DF for ; Tue, 4 Aug 2020 16:39:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 17AF3204EA for ; Tue, 4 Aug 2020 16:39:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=ffwll.ch header.i=@ffwll.ch header.b="IN6t6bbE" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729781AbgHDQjs (ORCPT ); Tue, 4 Aug 2020 12:39:48 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49214 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728678AbgHDQjq (ORCPT ); Tue, 4 Aug 2020 12:39:46 -0400 Received: from mail-wr1-x443.google.com (mail-wr1-x443.google.com [IPv6:2a00:1450:4864:20::443]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1B676C06174A for ; Tue, 4 Aug 2020 09:39:43 -0700 (PDT) Received: by mail-wr1-x443.google.com with SMTP id 88so38001020wrh.3 for ; Tue, 04 Aug 2020 09:39:43 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ffwll.ch; s=google; h=date:from:to:cc:subject:message-id:mail-followup-to:references :mime-version:content-disposition:in-reply-to; bh=JuoBRwybPo1fWFUEbP61Iiw0shO0ZWJeZNUhHhFFSik=; b=IN6t6bbEriwy5B0+cBII5zTqrUsLuw6IiJLJi2iTwX+xkmzib/8A99wXPIkBQz4/XZ 2tqqV+1l9ZxR1VkXrgfcVD8Og8PouW4mMGocWHGph7kYSh15Aw4CGCkO08b3P+pMmqi6 Z/so2jerKEmn7prTPEkGDVeJraZlFBOTNAYJo= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id :mail-followup-to:references:mime-version:content-disposition :in-reply-to; bh=JuoBRwybPo1fWFUEbP61Iiw0shO0ZWJeZNUhHhFFSik=; b=byBOkEM13Ycjrdhx1rCqbhucEq4pfnQZTexjka3q/zx8CFIsFyTxLEObPVzKlEwkA3 g1BSRLi3xPuvgePSLuWmmyVbD09W1SCCecfl9zURVsNhHTbGLCxuL82dBIQO+cehBygw V6sBIh2an7EMYeY6sYGV47SKnFd0KXBtc0irWLQpz/NwAwOhEuIszqC/sHYqRp0NjhgX OUzWCbPC2gn/Pto1pzhH/CczDepMm6i3UTL1O98iKGOaupEfPnvuocLSmv4BN/EtPVYp 9NKXmoFu+5gQt/LD1gHIAh+dkPUcO8JGTHIEOe8jiaD4MHEDynCFm5KgfChMg3HKF5OW Ws5w== X-Gm-Message-State: AOAM533+CCHCHldcqbJMlocJYMdyOaaHPoQJzoP9fpiD7K+BcYMT16Dp 3BldYpkMhadojZbT5H1R8HzXxQ== X-Google-Smtp-Source: ABdhPJyndQxukD3h1NEdBq4GcWX84ZlX51VAfBQMBVVX9HzgwhENu/HdYjrzvFisAeSIPiJXaAhr/Q== X-Received: by 2002:a5d:6a4a:: with SMTP id t10mr21416131wrw.360.1596559181804; Tue, 04 Aug 2020 09:39:41 -0700 (PDT) Received: from phenom.ffwll.local ([2a02:168:57f4:0:efd0:b9e5:5ae6:c2fa]) by smtp.gmail.com with ESMTPSA id v12sm31197854wrs.2.2020.08.04.09.39.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 04 Aug 2020 09:39:41 -0700 (PDT) Date: Tue, 4 Aug 2020 18:39:39 +0200 From: daniel@ffwll.ch Cc: Rodrigo Siqueira , Haneen Mohammed , Daniel Vetter , David Airlie , Rodrigo Siqueira , Sidong Yang , twoerner@gmail.com, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, kernel-usp@googlegroups.com Subject: Re: [PATCH] drm/vkms: guarantee vblank when capturing crc Message-ID: <20200804163939.GK6419@phenom.ffwll.local> Mail-Followup-To: Melissa Wen , Rodrigo Siqueira , Haneen Mohammed , David Airlie , Rodrigo Siqueira , Sidong Yang , twoerner@gmail.com, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, kernel-usp@googlegroups.com References: <20200801184929.2eaxyoq6fm3nk4ey@smtp.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200801184929.2eaxyoq6fm3nk4ey@smtp.gmail.com> X-Operating-System: Linux phenom 5.7.0-1-amd64 To: unlisted-recipients:; (no To-header on input) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Aug 01, 2020 at 03:49:29PM -0300, Melissa Wen wrote: > VKMS needs vblank interrupts enabled to capture CRC. When vblank is > disabled, tests like kms_cursor_crc and kms_pipe_crc_basic getting stuck > waiting for a capture that will not occur until vkms wakes up. This > patch ensures that vblank remains enabled as long as the CRC capture is > needed. > > It clears the execution of the following kms_cursor_crc subtests: > 1. pipe-A-cursor-[size,alpha-opaque, NxN-(on-screen, off-screen, sliding, > random, fast-moving])] - successful when running individually. > 2. pipe-A-cursor-dpms passes again > 3. pipe-A-cursor-suspend also passes > > The issue was initially tracked in the sequential execution of IGT > kms_cursor_crc subtest: when running the test sequence or one of its > subtests twice, the odd execs complete and the pairs get stuck in an > endless wait. In the IGT code, calling a wait_for_vblank on preparing > for CRC capture prevented the busy-wait. But the problem persisted in > the pipe-A-cursor-dpms and -suspend subtests. > > Checking the history, the pipe-A-cursor-dpms subtest was successful > when, in vkms_atomic_commit_tail, instead of using the flip_done op, it > used wait_for_vblanks. Another way to prevent blocking was > wait_one_vblank when enabling crtc. However, in both cases, > pipe-A-cursor-suspend persisted blocking in the 2nd start of CRC > capture, which may indicate that something got stuck in the step of CRC > setup. Indeed, wait_one_vblank in the crc setup was able to sync things > and free all kms_cursor_crc subtests. > > Besides, other alternatives to force enabling vblanks or prevent > disabling them such as calling drm_crtc_put_vblank or modeset_enables > before commit_planes + offdelay = 0, also unlock all subtests > executions. These facts together converge on the lack of vblank to > unblock the crc capture. > > Finally, considering the vkms's dependence on vblank interruptions to > perform tasks, this patch acquires a vblank ref when setup CRC source > and releases ref when disabling crc capture, ensuring vblanks happen to > compute CRC. > > Cc: Rodrigo Siqueira > Cc: Haneen Mohammed > Co-developed-by: Sidong Yang > Signed-off-by: Sidong Yang > Co-developed-by: Daniel Vetter > Signed-off-by: Daniel Vetter > Signed-off-by: Melissa Wen Excellent summary of the debug story. > --- > drivers/gpu/drm/vkms/vkms_composer.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/drivers/gpu/drm/vkms/vkms_composer.c b/drivers/gpu/drm/vkms/vkms_composer.c > index 4af2f19480f4..1161eaa383f1 100644 > --- a/drivers/gpu/drm/vkms/vkms_composer.c > +++ b/drivers/gpu/drm/vkms/vkms_composer.c > @@ -241,6 +241,14 @@ int vkms_set_crc_source(struct drm_crtc *crtc, const char *src_name) > > ret = vkms_crc_parse_source(src_name, &enabled); > > + /* Ensure that vblank interruptions are enabled for crc capture */ > + /* Enabling CRC: acquire vblank ref */ This comment just explains what the code does, that's not needed. The first comment I think can be replaced if we create a little helper function like void vkms_set_composer(struct vkms_output, bool enable) { bool old_state; if (enabled) drm_crtc_vblank_get(crtc); spin_lock_irq(&out->lock); old_enable = out->composer_enabled; out->composer_enabled = enabled; spin_unlock_irq(&out->lock); if (old_enabled) drm_crtc_vblank_put(crtc); } This should also help as prep for the writeback work, where we have a 2nd user that might need to enable the composer (maybe even need to switch to refcounting the composer state then). > + if (enabled) > + drm_crtc_vblank_get(crtc); > + /* Disabling CRC: release vblank ref */ > + if (!src_name) > + drm_crtc_vblank_put(crtc); I'm not sure this correctly releases the vblank reference in all cases, I think the suggestion in the helper function pseudo code should work better. It does mean we temporarily elevate the vblank refcount if we go enabled -> enabled, but that's not a problem since it's refcounted. Cheers, Daniel > + > spin_lock_irq(&out->lock); > out->composer_enabled = enabled; > spin_unlock_irq(&out->lock); > -- > 2.27.0 > -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch