From patchwork Thu Apr 23 16:42:24 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Lyude Paul X-Patchwork-Id: 11506039 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 0801D14DD for ; Thu, 23 Apr 2020 16:42:59 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id D9EFA20728 for ; Thu, 23 Apr 2020 16:42:58 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Qc0rvV6p" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D9EFA20728 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=dri-devel-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 8586C6E8FA; Thu, 23 Apr 2020 16:42:56 +0000 (UTC) X-Original-To: dri-devel@lists.freedesktop.org Delivered-To: dri-devel@lists.freedesktop.org Received: from us-smtp-1.mimecast.com (us-smtp-delivery-1.mimecast.com [205.139.110.120]) by gabe.freedesktop.org (Postfix) with ESMTPS id 67FCF6E8FA for ; Thu, 23 Apr 2020 16:42:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1587660173; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=odJrFOK+7bivbDZ7ZKaNo+MENCGaQCojnN8HH0MbtLQ=; b=Qc0rvV6pj3O0qxkfNU5dT+4WejmMcUIFPYptm50q6/d9d/uKwZqgNLfvS74Bqe9G1WaLWQ CQTJRIXrxbNB8e+s2cSb76uWB7E+1Y4sm0D/RRYAPY9dRVZXGMI/IEUcfKQx+KBboCm8/j 0rFTviRP/tlRnWxm+HHegOcOmRSoLUI= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-394-uYnyQ5tLMYyrRTydAnFg0Q-1; Thu, 23 Apr 2020 12:42:49 -0400 X-MC-Unique: uYnyQ5tLMYyrRTydAnFg0Q-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id CB72F803786; Thu, 23 Apr 2020 16:42:30 +0000 (UTC) Received: from Ruby.redhat.com (ovpn-119-186.rdu2.redhat.com [10.10.119.186]) by smtp.corp.redhat.com (Postfix) with ESMTP id 7F7545D9CC; Thu, 23 Apr 2020 16:42:28 +0000 (UTC) From: Lyude Paul To: dri-devel@lists.freedesktop.org Subject: [PATCH] Revert "drm/dp_mst: Remove single tx msg restriction." Date: Thu, 23 Apr 2020 12:42:24 -0400 Message-Id: <20200423164225.680178-1-lyude@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: David Airlie , linux-kernel@vger.kernel.org, Sean Paul , Thomas Zimmermann , Wayne Lin , Wayne Lin Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" This reverts commit 6bb0942e8f46863a745489cce27efe5be2a3885e. Unfortunately it would appear that the rumors we've heard of sideband message interleaving not being very well supported are true. On the Lenovo ThinkPad Thunderbolt 3 dock that I have, interleaved messages appear to just get dropped: [drm:drm_dp_mst_wait_tx_reply [drm_kms_helper]] timedout msg send 00000000571ddfd0 2 1 [dp_mst] txmsg cur_offset=2 cur_len=2 seqno=1 state=SENT path_msg=1 dst=00 [dp_mst] type=ENUM_PATH_RESOURCES contents: [dp_mst] port=2 DP descriptor for this hub: OUI 90-cc-24 dev-ID SYNA3 HW-rev 1.0 SW-rev 3.12 quirks 0x0008 It would seem like as well that this is a somewhat well known issue in the field. From section 5.4.2 of the DisplayPort 2.0 specification: There are MST Sink/Branch devices in the field that do not handle interleaved message transactions. To facilitate message transaction handling by downstream devices, an MST Source device shall generate message transactions in an atomic manner (i.e., the MST Source device shall not concurrently interleave multiple message transactions). Therefore, an MST Source device shall clear the Message_Sequence_No value in the Sideband_MSG_Header to 0. MST Source devices that support field policy updates by way of software should update the policy to forego the generation of interleaved message transactions. This is a bit disappointing, as features like HDCP require that we send a sideband request every ~2 seconds for each active stream. However, there isn't really anything in the specification that allows us to accurately probe for interleaved messages. If it ends up being that we -really- need this in the future, we might be able to whitelist hubs where interleaving is known to work-or maybe try some sort of heuristics. But for now, let's just play it safe and not use it. Signed-off-by: Lyude Paul Fixes: 6bb0942e8f46 ("drm/dp_mst: Remove single tx msg restriction.") Cc: Wayne Lin Cc: Sean Paul Reviewed-by: Sean Paul Acked-by: Harry Wentland Acked-by: Wayne Lin --- drivers/gpu/drm/drm_dp_mst_topology.c | 14 ++++++++++++-- include/drm/drm_dp_mst_helper.h | 5 +++++ 2 files changed, 17 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c index 21f10ceb3d6c..03a1496f6120 100644 --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -1205,6 +1205,8 @@ static int drm_dp_mst_wait_tx_reply(struct drm_dp_mst_branch *mstb, txmsg->state == DRM_DP_SIDEBAND_TX_SENT) { mstb->tx_slots[txmsg->seqno] = NULL; } + mgr->is_waiting_for_dwn_reply = false; + } out: if (unlikely(ret == -EIO) && drm_debug_enabled(DRM_UT_DP)) { @@ -1214,6 +1216,7 @@ static int drm_dp_mst_wait_tx_reply(struct drm_dp_mst_branch *mstb, } mutex_unlock(&mgr->qlock); + drm_dp_mst_kick_tx(mgr); return ret; } @@ -2789,9 +2792,11 @@ static void process_single_down_tx_qlock(struct drm_dp_mst_topology_mgr *mgr) ret = process_single_tx_qlock(mgr, txmsg, false); if (ret == 1) { /* txmsg is sent it should be in the slots now */ + mgr->is_waiting_for_dwn_reply = true; list_del(&txmsg->next); } else if (ret) { DRM_DEBUG_KMS("failed to send msg in q %d\n", ret); + mgr->is_waiting_for_dwn_reply = false; list_del(&txmsg->next); if (txmsg->seqno != -1) txmsg->dst->tx_slots[txmsg->seqno] = NULL; @@ -2831,7 +2836,8 @@ static void drm_dp_queue_down_tx(struct drm_dp_mst_topology_mgr *mgr, drm_dp_mst_dump_sideband_msg_tx(&p, txmsg); } - if (list_is_singular(&mgr->tx_msg_downq)) + if (list_is_singular(&mgr->tx_msg_downq) && + !mgr->is_waiting_for_dwn_reply) process_single_down_tx_qlock(mgr); mutex_unlock(&mgr->qlock); } @@ -3823,6 +3829,7 @@ static int drm_dp_mst_handle_down_rep(struct drm_dp_mst_topology_mgr *mgr) mutex_lock(&mgr->qlock); txmsg->state = DRM_DP_SIDEBAND_TX_RX; mstb->tx_slots[seqno] = NULL; + mgr->is_waiting_for_dwn_reply = false; mutex_unlock(&mgr->qlock); wake_up_all(&mgr->tx_waitq); @@ -3830,6 +3837,9 @@ static int drm_dp_mst_handle_down_rep(struct drm_dp_mst_topology_mgr *mgr) return 0; out_clear_reply: + mutex_lock(&mgr->qlock); + mgr->is_waiting_for_dwn_reply = false; + mutex_unlock(&mgr->qlock); if (msg) memset(msg, 0, sizeof(struct drm_dp_sideband_msg_rx)); out: @@ -4683,7 +4693,7 @@ static void drm_dp_tx_work(struct work_struct *work) struct drm_dp_mst_topology_mgr *mgr = container_of(work, struct drm_dp_mst_topology_mgr, tx_work); mutex_lock(&mgr->qlock); - if (!list_empty(&mgr->tx_msg_downq)) + if (!list_empty(&mgr->tx_msg_downq) && !mgr->is_waiting_for_dwn_reply) process_single_down_tx_qlock(mgr); mutex_unlock(&mgr->qlock); } diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h index 2d7c26592c05..96bcf33c03d3 100644 --- a/include/drm/drm_dp_mst_helper.h +++ b/include/drm/drm_dp_mst_helper.h @@ -592,6 +592,11 @@ struct drm_dp_mst_topology_mgr { */ bool payload_id_table_cleared : 1; + /** + * @is_waiting_for_dwn_reply: whether we're waiting for a down reply. + */ + bool is_waiting_for_dwn_reply : 1; + /** * @mst_primary: Pointer to the primary/first branch device. */