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=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 49CD1C432C0 for ; Tue, 3 Dec 2019 12:41:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 275E720684 for ; Tue, 3 Dec 2019 12:41:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726224AbfLCMlH (ORCPT ); Tue, 3 Dec 2019 07:41:07 -0500 Received: from mga03.intel.com ([134.134.136.65]:17530 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725997AbfLCMlH (ORCPT ); Tue, 3 Dec 2019 07:41:07 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga103.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 03 Dec 2019 04:41:07 -0800 X-IronPort-AV: E=Sophos;i="5.69,273,1571727600"; d="scan'208";a="204962080" Received: from jnikula-mobl3.fi.intel.com (HELO localhost) ([10.237.66.161]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 03 Dec 2019 04:41:03 -0800 From: Jani Nikula To: Lyude Paul , intel-gfx@lists.freedesktop.org Cc: Joonas Lahtinen , Rodrigo Vivi , David Airlie , Daniel Vetter , Chris Wilson , Maarten Lankhorst , Lee Shawn C , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 3/5] drm/i915: Fix DPCD register order in intel_dp_aux_enable_backlight() In-Reply-To: <20191122231616.2574-4-lyude@redhat.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo References: <20191122231616.2574-1-lyude@redhat.com> <20191122231616.2574-4-lyude@redhat.com> Date: Tue, 03 Dec 2019 14:41:00 +0200 Message-ID: <87r21lintv.fsf@intel.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 22 Nov 2019, Lyude Paul wrote: > For eDP panels, it appears it's expected that so long as the panel is in > DPCD control mode that the brightness value is never set to 0. Instead, > if the desired effect is to set the panel's backlight to 0 we're > expected to simply turn off the backlight through the > DP_EDP_DISPLAY_CONTROL_REGISTER. > > We already do the latter correctly in intel_dp_aux_disable_backlight(). > But, we make the mistake of writing the DPCD registers in the wrong > order when enabling the backlight in intel_dp_aux_enable_backlight() > since we currently enable the backlight through > DP_EDP_DISPLAY_CONTROL_REGISTER before writing the brightness level. On > the X1 Extreme 2nd Generation, this appears to have the potential of > confusing the panel in such a way that further attempts to set the > brightness don't actually change the backlight as expected and leave it > off. Presumably, this happens because the incorrect register writing > order briefly leaves the panel with DPCD mode enabled and a 0 brightness > level set. > > So, reverse the order we write the DPCD registers when enabling the > panel backlight so that we write the brightness value first, and enable > the backlight second. This fix appears to be the final bit needed to get > the backlight on the ThinkPad X1 Extreme 2nd Generation's AMOLED screen > working. > > Signed-off-by: Lyude Paul Reviewed-by: Jani Nikula > --- > drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c > index 0bf8772bc7bb..87b59db9ffe3 100644 > --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c > +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c > @@ -205,8 +205,9 @@ static void intel_dp_aux_enable_backlight(const struct intel_crtc_state *crtc_st > } > } > > + intel_dp_aux_set_backlight(conn_state, > + connector->panel.backlight.level); > set_aux_backlight_enable(intel_dp, true); > - intel_dp_aux_set_backlight(conn_state, connector->panel.backlight.level); > } > > static void intel_dp_aux_disable_backlight(const struct drm_connector_state *old_conn_state) -- Jani Nikula, Intel Open Source Graphics Center