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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id DEA0FC433EF for ; Mon, 24 Jan 2022 21:47:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1573492AbiAXVo7 (ORCPT ); Mon, 24 Jan 2022 16:44:59 -0500 Received: from ams.source.kernel.org ([145.40.68.75]:47052 "EHLO ams.source.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1455850AbiAXVgT (ORCPT ); Mon, 24 Jan 2022 16:36:19 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 272A9B811FB; Mon, 24 Jan 2022 21:36:17 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 53EECC340E4; Mon, 24 Jan 2022 21:36:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1643060175; bh=bhbsw2fwuvSCgvtAyFmTD1Pr4flVhlB9Zn5rPk5BPmc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Jp7eubMoQOT0/kyQ7kOxJDT7JC2bTLXGHB7R/ZbdEsfSmTbUu9BODJUQggobB+oUZ 9DigAtqDdNsJjXtp77Qr1CXJvnivkeiyLBjgcrDf3ZFLAzNIEcqvQh0NAmZnEk2fmG Xm2yMxjdW4VX3uBfX+6TeWUFb03XHID1rMtK+pyw= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Zain Wang , Tomasz Figa , Heiko Stuebner , Sean Paul , Brian Norris , Robert Foss Subject: [PATCH 5.16 0863/1039] drm/bridge: analogix_dp: Make PSR-exit block less Date: Mon, 24 Jan 2022 19:44:12 +0100 Message-Id: <20220124184154.306579488@linuxfoundation.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220124184125.121143506@linuxfoundation.org> References: <20220124184125.121143506@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Brian Norris commit c4c6ef229593366ab593d4d424addc7025b54a76 upstream. Prior to commit 6c836d965bad ("drm/rockchip: Use the helpers for PSR"), "PSR exit" used non-blocking analogix_dp_send_psr_spd(). The refactor started using the blocking variant, for a variety of reasons -- quoting Sean Paul's potentially-faulty memory: """ - To avoid racing a subsequent PSR entry (if exit takes a long time) - To avoid racing disable/modeset - We're not displaying new content while exiting PSR anyways, so there is minimal utility in allowing frames to be submitted - We're lying to userspace telling them frames are on the screen when we're just dropping them on the floor """ However, I'm finding that this blocking transition is causing upwards of 60+ ms of unneeded latency on PSR-exit, to the point that initial cursor movements when leaving PSR are unbearably jumpy. It turns out that we need to meet in the middle somewhere: Sean is right that we were "lying to userspace" with a non-blocking PSR-exit, but the new blocking behavior is also waiting too long: According to the eDP specification, the sink device must support PSR entry transitions from both state 4 (ACTIVE_RESYNC) and state 0 (INACTIVE). It also states that in ACTIVE_RESYNC, "the Sink device must display the incoming active frames from the Source device with no visible glitches and/or artifacts." Thus, for our purposes, we only need to wait for ACTIVE_RESYNC before moving on; we are ready to display video, and subsequent PSR-entry is safe. Tested on a Samsung Chromebook Plus (i.e., Rockchip RK3399 Gru Kevin), where this saves about 60ms of latency, for PSR-exit that used to take about 80ms. Fixes: 6c836d965bad ("drm/rockchip: Use the helpers for PSR") Cc: Cc: Zain Wang Cc: Tomasz Figa Cc: Heiko Stuebner Cc: Sean Paul Signed-off-by: Brian Norris Reviewed-by: Sean Paul Signed-off-by: Robert Foss Link: https://patchwork.freedesktop.org/patch/msgid/20211103135112.v3.1.I67612ea073c3306c71b46a87be894f79707082df@changeid Signed-off-by: Greg Kroah-Hartman --- drivers/gpu/drm/bridge/analogix/analogix_dp_reg.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) --- a/drivers/gpu/drm/bridge/analogix/analogix_dp_reg.c +++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_reg.c @@ -998,11 +998,21 @@ int analogix_dp_send_psr_spd(struct anal if (!blocking) return 0; + /* + * db[1]!=0: entering PSR, wait for fully active remote frame buffer. + * db[1]==0: exiting PSR, wait for either + * (a) ACTIVE_RESYNC - the sink "must display the + * incoming active frames from the Source device with no visible + * glitches and/or artifacts", even though timings may still be + * re-synchronizing; or + * (b) INACTIVE - the transition is fully complete. + */ ret = readx_poll_timeout(analogix_dp_get_psr_status, dp, psr_status, psr_status >= 0 && ((vsc->db[1] && psr_status == DP_PSR_SINK_ACTIVE_RFB) || - (!vsc->db[1] && psr_status == DP_PSR_SINK_INACTIVE)), 1500, - DP_TIMEOUT_PSR_LOOP_MS * 1000); + (!vsc->db[1] && (psr_status == DP_PSR_SINK_ACTIVE_RESYNC || + psr_status == DP_PSR_SINK_INACTIVE))), + 1500, DP_TIMEOUT_PSR_LOOP_MS * 1000); if (ret) { dev_warn(dp->dev, "Failed to apply PSR %d\n", ret); return ret;