From patchwork Fri Mar 7 18:31:52 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Imre Deak X-Patchwork-Id: 14006951 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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 3FA94C28B23 for ; Fri, 7 Mar 2025 18:31:58 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 4605310E6B0; Fri, 7 Mar 2025 18:31:57 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=intel.com header.i=@intel.com header.b="jp3H5PjS"; dkim-atps=neutral Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.9]) by gabe.freedesktop.org (Postfix) with ESMTPS id 2626A10E69D; Fri, 7 Mar 2025 18:31:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1741372316; x=1772908316; h=from:to:cc:subject:date:message-id:mime-version: content-transfer-encoding; bh=xAPoOl5E6d6FFqkDAmVH1nYHQECWj7e0x4LjKlRP2os=; b=jp3H5PjSpbzu6XetAUezK6UHEtNbuwX98Ss+LY+BMxxzcFTrk2rHs6sV TNb4OvoF6AYeULG/D3e4vTA/wOtiTaralXKYFk8WbwamC51Iwli5cq2Yg vnAI61hGcJo6AEodGbY4TamPw5leEYhPbqtWJTYZxE7GlCY1VAoxsB3jJ 0L0gsBDBsORWCb6hB6OSaMj0YyrGQrUFdzFDOySzMTxpc++fD/oj+9D0F t9h3UHcfGj/S1qRagOi82j+0U5cgOdyy7sKE+Z5Bo/YSOburMG9t0gRqG HjAajm14ffoc6LusgwLoyBF55FmDERGZxLJhanU3k+kczNbqUB2X3junx w==; X-CSE-ConnectionGUID: wehW+klIQ82r0/xQPXheHQ== X-CSE-MsgGUID: OkJakdSdSp2UD3nk2sl75A== X-IronPort-AV: E=McAfee;i="6700,10204,11365"; a="53068599" X-IronPort-AV: E=Sophos;i="6.14,229,1736841600"; d="scan'208";a="53068599" Received: from orviesa010.jf.intel.com ([10.64.159.150]) by fmvoesa103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 Mar 2025 10:31:55 -0800 X-CSE-ConnectionGUID: CSVWqhpaSY+g8/AVtpBBYw== X-CSE-MsgGUID: IerteWPUQVm6CrmeYL8Tow== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.12,224,1728975600"; d="scan'208";a="119336588" Received: from ideak-desk.fi.intel.com ([10.237.72.78]) by orviesa010-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 Mar 2025 10:31:54 -0800 From: Imre Deak To: intel-gfx@lists.freedesktop.org, intel-xe@lists.freedesktop.org, dri-devel@lists.freedesktop.org Cc: Wayne Lin , Lyude Paul , stable@vger.kernel.org Subject: [PATCH] drm/dp_mst: Fix locking when skipping CSN before topology probing Date: Fri, 7 Mar 2025 20:31:52 +0200 Message-ID: <20250307183152.3822170-1-imre.deak@intel.com> X-Mailer: git-send-email 2.44.2 MIME-Version: 1.0 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: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" The handling of the MST Connection Status Notify message is skipped if the probing of the topology is still pending. Acquiring the drm_dp_mst_topology_mgr::probe_lock for this in drm_dp_mst_handle_up_req() is problematic: the task/work this function is called from is also responsible for handling MST down-request replies (in drm_dp_mst_handle_down_rep()). Thus drm_dp_mst_link_probe_work() - holding already probe_lock - could be blocked waiting for an MST down-request reply while drm_dp_mst_handle_up_req() is waiting for probe_lock while processing a CSN message. This leads to the probe work's down-request message timing out. A scenario similar to the above leading to a down-request timeout is handling a CSN message in drm_dp_mst_handle_conn_stat(), holding the probe_lock and sending down-request messages while a second CSN message sent by the sink subsequently is handled by drm_dp_mst_handle_up_req(). Fix the above by moving the logic to skip the CSN handling to drm_dp_mst_process_up_req(). This function is called from a work (separate from the task/work handling new up/down messages), already holding probe_lock. This solves the above timeout issue, since handling of down-request replies won't be blocked by probe_lock. Fixes: ddf983488c3e ("drm/dp_mst: Skip CSN if topology probing is not done yet") Cc: Wayne Lin Cc: Lyude Paul Cc: stable@vger.kernel.org # v6.6+ Signed-off-by: Imre Deak --- drivers/gpu/drm/display/drm_dp_mst_topology.c | 40 +++++++++++-------- 1 file changed, 24 insertions(+), 16 deletions(-) diff --git a/drivers/gpu/drm/display/drm_dp_mst_topology.c b/drivers/gpu/drm/display/drm_dp_mst_topology.c index 8b68bb3fbffb0..3a1f1ffc7b552 100644 --- a/drivers/gpu/drm/display/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c @@ -4036,6 +4036,22 @@ static int drm_dp_mst_handle_down_rep(struct drm_dp_mst_topology_mgr *mgr) return 0; } +static bool primary_mstb_probing_is_done(struct drm_dp_mst_topology_mgr *mgr) +{ + bool probing_done = false; + + mutex_lock(&mgr->lock); + + if (mgr->mst_primary && drm_dp_mst_topology_try_get_mstb(mgr->mst_primary)) { + probing_done = mgr->mst_primary->link_address_sent; + drm_dp_mst_topology_put_mstb(mgr->mst_primary); + } + + mutex_unlock(&mgr->lock); + + return probing_done; +} + static inline bool drm_dp_mst_process_up_req(struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_pending_up_req *up_req) @@ -4066,8 +4082,12 @@ drm_dp_mst_process_up_req(struct drm_dp_mst_topology_mgr *mgr, /* TODO: Add missing handler for DP_RESOURCE_STATUS_NOTIFY events */ if (msg->req_type == DP_CONNECTION_STATUS_NOTIFY) { - dowork = drm_dp_mst_handle_conn_stat(mstb, &msg->u.conn_stat); - hotplug = true; + if (!primary_mstb_probing_is_done(mgr)) { + drm_dbg_kms(mgr->dev, "Got CSN before finish topology probing. Skip it.\n"); + } else { + dowork = drm_dp_mst_handle_conn_stat(mstb, &msg->u.conn_stat); + hotplug = true; + } } drm_dp_mst_topology_put_mstb(mstb); @@ -4149,10 +4169,11 @@ static int drm_dp_mst_handle_up_req(struct drm_dp_mst_topology_mgr *mgr) drm_dp_send_up_ack_reply(mgr, mst_primary, up_req->msg.req_type, false); + drm_dp_mst_topology_put_mstb(mst_primary); + if (up_req->msg.req_type == DP_CONNECTION_STATUS_NOTIFY) { const struct drm_dp_connection_status_notify *conn_stat = &up_req->msg.u.conn_stat; - bool handle_csn; drm_dbg_kms(mgr->dev, "Got CSN: pn: %d ldps:%d ddps: %d mcs: %d ip: %d pdt: %d\n", conn_stat->port_number, @@ -4161,16 +4182,6 @@ static int drm_dp_mst_handle_up_req(struct drm_dp_mst_topology_mgr *mgr) conn_stat->message_capability_status, conn_stat->input_port, conn_stat->peer_device_type); - - mutex_lock(&mgr->probe_lock); - handle_csn = mst_primary->link_address_sent; - mutex_unlock(&mgr->probe_lock); - - if (!handle_csn) { - drm_dbg_kms(mgr->dev, "Got CSN before finish topology probing. Skip it."); - kfree(up_req); - goto out_put_primary; - } } else if (up_req->msg.req_type == DP_RESOURCE_STATUS_NOTIFY) { const struct drm_dp_resource_status_notify *res_stat = &up_req->msg.u.resource_stat; @@ -4185,9 +4196,6 @@ static int drm_dp_mst_handle_up_req(struct drm_dp_mst_topology_mgr *mgr) list_add_tail(&up_req->next, &mgr->up_req_list); mutex_unlock(&mgr->up_req_lock); queue_work(system_long_wq, &mgr->up_req_work); - -out_put_primary: - drm_dp_mst_topology_put_mstb(mst_primary); out_clear_reply: reset_msg_rx_state(&mgr->up_req_recv); return ret;