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, 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 60259C32751 for ; Mon, 5 Aug 2019 15:11:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3CEBE21738 for ; Mon, 5 Aug 2019 15:11:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729770AbfHEPLy (ORCPT ); Mon, 5 Aug 2019 11:11:54 -0400 Received: from foss.arm.com ([217.140.110.172]:50566 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729133AbfHEPLy (ORCPT ); Mon, 5 Aug 2019 11:11:54 -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 AEE62337; Mon, 5 Aug 2019 08:11:53 -0700 (PDT) Received: from DESKTOP-E1NTVVP.cambridge.arm.com (ubuntu-vbox.cambridge.arm.com [10.1.36.122]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 86B793F694; Mon, 5 Aug 2019 08:11:52 -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] drm/crc-debugfs: Add notes about CRC<->commit interactions Date: Mon, 5 Aug 2019 16:11:43 +0100 Message-Id: <20190805151143.12317-1-brian.starkey@arm.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190802140910.GN7444@phenom.ffwll.local> References: <20190802140910.GN7444@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 --- I might have got the wrong end of the stick, but this is what I understood from what you said. Cheers, -Brian drivers/gpu/drm/drm_debugfs_crc.c | 15 +++++++++++---- include/drm/drm_crtc.h | 3 +++ 2 files changed, 14 insertions(+), 4 deletions(-) diff --git a/drivers/gpu/drm/drm_debugfs_crc.c b/drivers/gpu/drm/drm_debugfs_crc.c index 7ca486d750e9..1dff956bcc74 100644 --- a/drivers/gpu/drm/drm_debugfs_crc.c +++ b/drivers/gpu/drm/drm_debugfs_crc.c @@ -65,10 +65,17 @@ * 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). + * + * It's also possible that a "normal" commit via DRM_IOCTL_MODE_ATOMIC or the + * legacy paths may interfere with CRC generation. So, in the general case, + * userspace can't rely on the values in crtc-N/crc/data being valid + * across a commit. */ 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..0f7ea094a900 100644 --- a/include/drm/drm_crtc.h +++ b/include/drm/drm_crtc.h @@ -756,6 +756,8 @@ 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 a 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 +769,7 @@ 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