From patchwork Mon Feb 11 03:22:24 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mario Kleiner X-Patchwork-Id: 10805075 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 5FA171399 for ; Mon, 11 Feb 2019 03:22:51 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 4EA4229AF5 for ; Mon, 11 Feb 2019 03:22:51 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 431CC29AF7; Mon, 11 Feb 2019 03:22:51 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=2.0 tests=BAYES_00,DKIM_ADSP_CUSTOM_MED, FREEMAIL_FROM,MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id B967629AF5 for ; Mon, 11 Feb 2019 03:22:50 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 3EEF86E13D; Mon, 11 Feb 2019 03:22:43 +0000 (UTC) X-Original-To: dri-devel@lists.freedesktop.org Delivered-To: dri-devel@lists.freedesktop.org Received: from mail-wm1-x341.google.com (mail-wm1-x341.google.com [IPv6:2a00:1450:4864:20::341]) by gabe.freedesktop.org (Postfix) with ESMTPS id D9CF16E0EE; Mon, 11 Feb 2019 03:22:40 +0000 (UTC) Received: by mail-wm1-x341.google.com with SMTP id d15so14627503wmb.3; Sun, 10 Feb 2019 19:22:40 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=aUgaiamsxd0F5YBMAsN3rEhaeOiEltCMxggsxzGz9GY=; b=q/2Znu4A2pf/++g5imcjsvhK67O5+EhNaSVRm4iE/tg9LjbhOUb/UGrI2pSAWgVQRu PxYS0uYf4D7OxhUMS//5YjlFgnRK63XyvVlSknhChchbBiJKc4xouM7wZM3jxrmlS878 GUG0IZ/6d9beOoWlDKvz43hSjtNTC+b9O3jIwKoTzAIiv31tNgfBrtg7DVdZh314MGEc j0JkUu6NHUwKJo4I3Xs7wl1i7r72X9ze8FMSc34nQzR3FbkbvSESS2XFX+kEGANSosUf VGfFbmHnCViBwaW4IYgP3CCI9Jrwbya8zk6EQdVxaG1m3htnFkIPCxO3kfI/BEnbkFdy hoQQ== X-Gm-Message-State: AHQUAuZkR+8j/GJvxv56W8Oz8PyW+m38xCsZppqUOctgVrxO97+3nxuI 6GKsvb1aCF/vjCoQaGEykNvU85RF X-Google-Smtp-Source: AHgI3IZHBObIURpWZ6/FhWBugR8ZBsx8odN6Lo9GZOVbrwizh2PnyzsXX4V6E3e/LFhg0ZYsQM3q1Q== X-Received: by 2002:a5d:6b8b:: with SMTP id n11mr24759174wrx.216.1549855359243; Sun, 10 Feb 2019 19:22:39 -0800 (PST) Received: from twisty.cin.medizin.uni-tuebingen.de ([2a01:c23:8429:3400:e9fd:d3f1:412c:598a]) by smtp.gmail.com with ESMTPSA id m21sm19379971wmi.43.2019.02.10.19.22.38 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 10 Feb 2019 19:22:38 -0800 (PST) From: Mario Kleiner To: amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org Subject: [PATCH 2/3] drm: Add basic helper to allow precise pageflip timestamps in vrr. Date: Mon, 11 Feb 2019 04:22:24 +0100 Message-Id: <20190211032225.9488-3-mario.kleiner.de@gmail.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190211032225.9488-1-mario.kleiner.de@gmail.com> References: <20190211032225.9488-1-mario.kleiner.de@gmail.com> X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Alex Deucher , michel@daenzer.net, Nicholas Kazlauskas MIME-Version: 1.0 Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" X-Virus-Scanned: ClamAV using ClamSMTP The pageflip completion timestamps transmitted to userspace via pageflip completion events are supposed to describe the time at which the first pixel of the new post-pageflip scanout buffer leaves the video output of the gpu. This time is identical to end of vblank, when active scanout starts. For a crtc in standard fixed refresh rate, the end of vblank is identical to the vblank timestamps calculated by drm_update_vblank_count() at each vblank interrupt, or each vblank dis-/enable. Therefore pageflip events just carry that vblank timestamp as their pageflip timestamp. For a crtc switched to variable refresh rate mode (vrr), the pageflip completion timestamps are identical to the vblank timestamps iff the pageflip was executed early in vblank, before the minimum vblank duration elapsed. In this case the time of display onset is identical to when the crtc is running in fixed refresh rate. However, if a pageflip completes later in the vblank, inside the "extended front porch" in vrr mode, then the vblank will terminate at a fixed (back porch) duration after flip, so the display onset time is delayed correspondingly. In this case the vblank timestamp computed at vblank irq time would be too early, and we need a way to calculate an estimated pageflip timestamp that will be later than the vblank timestamp. How a driver determines such a "late flip" timestamp is hw and driver specific, but this patch adds a new helper function that allows the driver to propose such an alternate "late flip" timestamp for use in pageflip events: drm_crtc_set_vrr_pageflip_timestamp(crtc, flip_timestamp); When sending out pageflip events, we now compare that proposed flip_timestamp against the vblank timestamp of the current vblank of flip completion and choose to send out the greater/ later timestamp as flip completion timestamp. The most simple way for a kms driver to supply a suitable flip_timestamp in vrr mode would be to simply take a timestamp at start of the pageflip completion handler, e.g., pageflip irq handler: flip_timestamp = ktime_get(); and then set that as proposed "late" alternative timestamp via ... drm_crtc_set_vrr_pageflip_timestamp(crtc, flip_timestamp); More clever approaches could try to add some corrective offset for fixed back porch duration, or ideally use hardware features like hw timestamps to calculate the exact end time of vblank. Signed-off-by: Mario Kleiner Cc: Nicholas Kazlauskas Cc: Harry Wentland Cc: Alex Deucher --- drivers/gpu/drm/drm_vblank.c | 49 +++++++++++++++++++++++++++++++++++- include/drm/drm_vblank.h | 8 ++++++ 2 files changed, 56 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c index 98e091175921..4b3a4c38fabe 100644 --- a/drivers/gpu/drm/drm_vblank.c +++ b/drivers/gpu/drm/drm_vblank.c @@ -814,10 +814,21 @@ static void send_vblank_event(struct drm_device *dev, u64 seq, ktime_t now) { struct timespec64 tv; + ktime_t alt_flip_time; switch (e->event.base.type) { - case DRM_EVENT_VBLANK: case DRM_EVENT_FLIP_COMPLETE: + /* + * For flip completion events, override "now" time + * with alt_flip_time provided by the driver via + * drm_crtc_set_vrr_pageflip_timestamp() in VRR mode + * if that time is later than given "now" vblank time. + */ + alt_flip_time = dev->vblank[e->pipe].alt_flip_time; + if (alt_flip_time > now) + now = alt_flip_time; + /* Fallthrough */ + case DRM_EVENT_VBLANK: tv = ktime_to_timespec64(now); e->event.vbl.sequence = seq; /* @@ -916,11 +927,47 @@ void drm_crtc_send_vblank_event(struct drm_crtc *crtc, now = ktime_get(); } + e->pipe = pipe; send_vblank_event(dev, e, seq, now); } EXPORT_SYMBOL(drm_crtc_send_vblank_event); +/** + * drm_crtc_set_vrr_pageflip_timestamp - helper to set alternate pageflip time + * @crtc: the source CRTC of the pageflip completion event + * @flip_time: The alternate pageflip completion timestamp in VRR mode + * + * In variable refresh rate mode (VRR), a pageflip completion timestamp carried + * by the pageflip event can never be earlier than the vblank timestamp of the + * vblank of flip completion, as that vblank timestamp defines the end of the + * shortest possible vblank duration. In case of a delayed flip completion + * inside the extended VRR front porch however, the end of vblank can be much + * later, so the driver must assign an estimated timestamp of that later end of + * vblank. For a CRTC in VRR mode, the driver should use this helper function to + * set an alternate flip completion timestamp in case of late flip completions + * in extended vblank. In the most simple case, this @flip_time timestamp could + * simply be a ktime_get() timestamp taken at the start of the pageflip + * completion routine, with some constant duration of the back porch interval + * added, although more precise estimates may be possible on some hardware if + * the hardware provides some means of timestamping the true end of vblank. + * + * When sending out pageflip events, e.g., via drm_crtc_send_vblank_event(), it + * will use either the standard vblank timestamp, calculated for a minimum + * duration vblank, or the provided @flip_time if that time is later than the + * vblank timestamp, to get the best possible estimate of start of display of + * the new post-pageflip scanout buffer. + */ +void drm_crtc_set_vrr_pageflip_timestamp(struct drm_crtc *crtc, + ktime_t flip_time) +{ + struct drm_device *dev = crtc->dev; + struct drm_vblank_crtc *vblank = &dev->vblank[drm_crtc_index(crtc)]; + + vblank->alt_flip_time = flip_time; +} +EXPORT_SYMBOL(drm_crtc_set_vrr_pageflip_timestamp); + static int __enable_vblank(struct drm_device *dev, unsigned int pipe) { if (drm_core_check_feature(dev, DRIVER_MODESET)) { diff --git a/include/drm/drm_vblank.h b/include/drm/drm_vblank.h index 6ad9630d4f48..aacf44694ab6 100644 --- a/include/drm/drm_vblank.h +++ b/include/drm/drm_vblank.h @@ -117,6 +117,12 @@ struct drm_vblank_crtc { * @time: Vblank timestamp corresponding to @count. */ ktime_t time; + /** + * @alt_flip_time: Vblank timestamp for end of extended vblank due to + * a late pageflip completion in variable refresh rate mode. Pageflip + * events will carry the later one of @time and @alt_flip_time. + */ + ktime_t alt_flip_time; /** * @refcount: Number of users/waiters of the vblank interrupt. Only when @@ -179,6 +185,8 @@ int drm_vblank_init(struct drm_device *dev, unsigned int num_crtcs); u64 drm_crtc_vblank_count(struct drm_crtc *crtc); u64 drm_crtc_vblank_count_and_time(struct drm_crtc *crtc, ktime_t *vblanktime); +void drm_crtc_set_vrr_pageflip_timestamp(struct drm_crtc *crtc, + ktime_t flip_time); void drm_crtc_send_vblank_event(struct drm_crtc *crtc, struct drm_pending_vblank_event *e); void drm_crtc_arm_vblank_event(struct drm_crtc *crtc,