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=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,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 1F1D6C433FF for ; Tue, 6 Aug 2019 10:48:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F0C2A20818 for ; Tue, 6 Aug 2019 10:48:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732670AbfHFKso (ORCPT ); Tue, 6 Aug 2019 06:48:44 -0400 Received: from foss.arm.com ([217.140.110.172]:60124 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728845AbfHFKso (ORCPT ); Tue, 6 Aug 2019 06:48:44 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 6C036337; Tue, 6 Aug 2019 03:48:43 -0700 (PDT) Received: from DESKTOP-E1NTVVP.cambridge.arm.com (unknown [10.1.25.192]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 427DB3F694; Tue, 6 Aug 2019 03:48:42 -0700 (PDT) From: Brian Starkey To: Liviu Dudau , "james qian wang (Arm Technology China)" , "Lowry Li (Arm Technology China)" , nd@arm.com, Daniel Vetter Cc: dri-devel@lists.freedesktop.org, LKML Subject: [PATCH v2] drm/crc-debugfs: Add notes about CRC<->commit interactions Date: Tue, 6 Aug 2019 11:48:35 +0100 Message-Id: <20190806104835.26075-1-brian.starkey@arm.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190806091233.GX7444@phenom.ffwll.local> References: <20190806091233.GX7444@phenom.ffwll.local> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org CRC generation can be impacted by commits coming from userspace, and enabling CRC generation may itself trigger a commit. Add notes about this to the kerneldoc. Signed-off-by: Brian Starkey --- drivers/gpu/drm/drm_debugfs_crc.c | 17 +++++++++++++---- include/drm/drm_crtc.h | 4 ++++ 2 files changed, 17 insertions(+), 4 deletions(-) diff --git a/drivers/gpu/drm/drm_debugfs_crc.c b/drivers/gpu/drm/drm_debugfs_crc.c index 7ca486d750e9..77159b6e77c3 100644 --- a/drivers/gpu/drm/drm_debugfs_crc.c +++ b/drivers/gpu/drm/drm_debugfs_crc.c @@ -65,10 +65,19 @@ * it submits. In this general case, the maximum userspace can do is to compare * the reported CRCs of frames that should have the same contents. * - * On the driver side the implementation effort is minimal, drivers only need to - * implement &drm_crtc_funcs.set_crc_source. The debugfs files are automatically - * set up if that vfunc is set. CRC samples need to be captured in the driver by - * calling drm_crtc_add_crc_entry(). + * On the driver side the implementation effort is minimal, drivers only need + * to implement &drm_crtc_funcs.set_crc_source. The debugfs files are + * automatically set up if that vfunc is set. CRC samples need to be captured + * in the driver by calling drm_crtc_add_crc_entry(). Depending on the driver + * and HW requirements, &drm_crtc_funcs.set_crc_source may result in a commit + * (even a full modeset). + * + * CRC results must be reliable across non-full-modeset atomic commits, so if a + * commit via DRM_IOCTL_MODE_ATOMIC would disable or otherwise interfere with + * CRC generation, then the driver must mark that commit as a full modeset + * (drm_atomic_crtc_needs_modeset() should return true). As a result, to ensure + * consistent results, generic userspace must re-setup CRC generation after a + * legacy SETCRTC or an atomic commit with DRM_MODE_ATOMIC_ALLOW_MODESET. */ static int crc_control_show(struct seq_file *m, void *data) diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h index 128d8b210621..7d14c11bdc0a 100644 --- a/include/drm/drm_crtc.h +++ b/include/drm/drm_crtc.h @@ -756,6 +756,9 @@ struct drm_crtc_funcs { * provided from the configured source. Drivers must accept an "auto" * source name that will select a default source for this CRTC. * + * This may trigger an atomic modeset commit if necessary, to enable CRC + * generation. + * * Note that "auto" can depend upon the current modeset configuration, * e.g. it could pick an encoder or output specific CRC sampling point. * @@ -767,6 +770,7 @@ struct drm_crtc_funcs { * 0 on success or a negative error code on failure. */ int (*set_crc_source)(struct drm_crtc *crtc, const char *source); + /** * @verify_crc_source: * -- 2.17.1