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=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED, USER_AGENT_MUTT autolearn=unavailable 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 6416EC282C8 for ; Mon, 28 Jan 2019 12:44:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3FBBF21773 for ; Mon, 28 Jan 2019 12:44:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726744AbfA1Mot (ORCPT ); Mon, 28 Jan 2019 07:44:49 -0500 Received: from mga07.intel.com ([134.134.136.100]:36642 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726647AbfA1Mot (ORCPT ); Mon, 28 Jan 2019 07:44:49 -0500 X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by orsmga105.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 28 Jan 2019 04:44:48 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.56,534,1539673200"; d="scan'208";a="138469864" Received: from ideak-desk.fi.intel.com ([10.237.72.62]) by fmsmga002.fm.intel.com with ESMTP; 28 Jan 2019 04:44:45 -0800 Date: Mon, 28 Jan 2019 14:44:45 +0200 From: Imre Deak To: Lyude Paul Cc: intel-gfx@lists.freedesktop.org, Todd Previte , David Airlie , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Dave Airlie Subject: Re: [Intel-gfx] [PATCH] drm/i915: Don't send MST hotplugs until after resume Message-ID: <20190128124445.GG12107@ideak-desk.fi.intel.com> Reply-To: imre.deak@intel.com References: <20190126012436.31382-1-lyude@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190126012436.31382-1-lyude@redhat.com> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jan 25, 2019 at 08:24:35PM -0500, Lyude Paul wrote: > Turns out we are sending a lot more hotplug events then we need, and > this is causing some pretty serious issues. Currently, we call > intel_dp_mst_resume() in i915_drm_resume() well before we have any sort > of hotplugging setup. We call hpd_irq_setup() before calling intel_dp_mst_resume(). The only purpose of that part (lifted out from intel_hpd_init()) is to provide the short HPD interrupt functionality MST AUX transfers need. But you are right in that - as a side-effect - we'll also enable generic hotplug functionality that is independent of the above MST requirement. Doing that kind of generic hotplug processing before intel_display_resume() is probably not a good idea, it can interfere at least with the mode restore in __intel_display_resume(). > This is a pretty big problem, because in practice it will generally > result in throwing the power domain refcounts out of wack. > > For instance: On my T480s, removing a previously connected topology > before the system finishes resuming causes > drm_kms_helper_hotplug_event() to be called before HPD is setup again, > which causes us to do a connector reprobe, which then causes > intel_dp_detect() to be called on all DP devices -including- the eDP > display. From there, intel_dp_detect() is run on the eDP display which > triggers DPCD transactions. Those DPCD transactions then cause us to > call edp_panel_vdd_on(), which then causes us to grab an additional > wakeref to the relevant power wells (PORT_DDI_A_IO on this machine). > From there, this wakeref is never released which then causes the next > suspend/resume cycle to entirely fail due to the hardware not being > powered off correctly. > > This sucks really badly, and I don't see any decent way to actually fix > this in intel_dp_detect() easily. Additionally, I don't even think it'd > be worth the time now since we're not expecting to handle any kind of > connector reprobing at the point in which we call intel_dp_mst_resume(), > but we also can't move intel_dp_mst_resume() any higher in the resume > process since MST topologies need to be resumed before > intel_display_resume() is called. > > However, there's a light at the end of the tunnel! After reading through > a lot of code dozens of times, it occurred to me that we -never- > actually need to send hotplug events when calling > drm_dp_mst_topology_mgr_set_mst() since we send hotplug events in > drm_dp_destroy_connector_work(). Imagine that! > > So, since we only seem to call intel_dp_mst_check_status() to disable > MST on the encoder in question and then send a hotplug, get rid of this > and instead just disable MST mode when a hub fails in > intel_dp_mst_resume(). From there, drm_dp_destroy_connector_work() will > eventually send the hotplug event. > > Signed-off-by: Lyude Paul > Fixes: 0e32b39ceed6 ("drm/i915: add DP 1.2 MST support (v0.7)") > Cc: Todd Previte > Cc: Dave Airlie > Cc: Jani Nikula > Cc: Joonas Lahtinen > Cc: Rodrigo Vivi > Cc: intel-gfx@lists.freedesktop.org > Cc: # v3.17+ Not knowing enough about the MST code, but we do need to prevent generic hotplug processing at this point: Acked-by: Imre Deak > --- > drivers/gpu/drm/i915/intel_dp.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c > index 681e88405ada..c2399acf177b 100644 > --- a/drivers/gpu/drm/i915/intel_dp.c > +++ b/drivers/gpu/drm/i915/intel_dp.c > @@ -7096,7 +7096,10 @@ void intel_dp_mst_resume(struct drm_i915_private *dev_priv) > continue; > > ret = drm_dp_mst_topology_mgr_resume(&intel_dp->mst_mgr); > - if (ret) > - intel_dp_check_mst_status(intel_dp); > + if (ret) { > + intel_dp->is_mst = false; > + drm_dp_mst_topology_mgr_set_mst(&intel_dp->mst_mgr, > + false); > + } > } > } > -- > 2.20.1 > > _______________________________________________ > Intel-gfx mailing list > Intel-gfx@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/intel-gfx