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=-16.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 85809C43381 for ; Thu, 18 Mar 2021 17:03:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 563D164F24 for ; Thu, 18 Mar 2021 17:03:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232160AbhCRRCb (ORCPT ); Thu, 18 Mar 2021 13:02:31 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:47733 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232125AbhCRRCQ (ORCPT ); Thu, 18 Mar 2021 13:02:16 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1616086935; 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=aaIWi/Aa75Hr56eti79lKQowFccyYMrkVkBuTxfGEhk=; b=YVFz/JDRMjCqyoJcJDVcmOr6RvTFR6PiV2rcja1ksY6aMF+ftFMRCePXb7mqeOX+13uXvM GeF+e1QVIhJzID11OTOztHmkmkZC9NG1P7bxWpGaoRUlM62JVtQssm44jps4GCSRn1QkpT S270WycbgrVK4tUVbCLFtOJ9snqN5Do= 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-327-QzJu-dWLNPiT0vYhS6dp9g-1; Thu, 18 Mar 2021 13:02:11 -0400 X-MC-Unique: QzJu-dWLNPiT0vYhS6dp9g-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id BB50B190A7A1; Thu, 18 Mar 2021 17:02:09 +0000 (UTC) Received: from Whitewolf.lyude.net (ovpn-113-18.rdu2.redhat.com [10.10.113.18]) by smtp.corp.redhat.com (Postfix) with ESMTP id 1192019D9B; Thu, 18 Mar 2021 17:02:07 +0000 (UTC) From: Lyude Paul To: intel-gfx@lists.freedesktop.org Cc: Jani Nikula , Rodrigo Vivi , Jani Nikula , Joonas Lahtinen , David Airlie , Daniel Vetter , Sean Paul , Aaron Ma , Dave Airlie , dri-devel@lists.freedesktop.org (open list:DRM DRIVERS), linux-kernel@vger.kernel.org (open list) Subject: [PATCH] drm/i915/dpcd_bl: Don't try vesa interface unless specified by VBT Date: Thu, 18 Mar 2021 13:02:02 -0400 Message-Id: <20210318170204.513000-1-lyude@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Looks like that there actually are another subset of laptops on the market that don't support the Intel HDR backlight interface, but do advertise support for the VESA DPCD backlight interface despite the fact it doesn't seem to work. Note though I'm not entirely clear on this - on one of the machines where this issue was observed, I also noticed that we appeared to be rejecting the VBT defined backlight frequency in intel_dp_aux_vesa_calc_max_backlight(). It's noted in this function that: /* Use highest possible value of Pn for more granularity of brightness * adjustment while satifying the conditions below. * ... * - FxP is within 25% of desired value. * Note: 25% is arbitrary value and may need some tweak. */ So it's possible that this value might just need to be tweaked, but for now let's just disable the VESA backlight interface unless it's specified in the VBT just to be safe. We might be able to try enabling this again by default in the future. Fixes: 2227816e647a ("drm/i915/dp: Allow forcing specific interfaces through enable_dpcd_backlight") Cc: Jani Nikula Cc: Rodrigo Vivi Bugzilla: https://gitlab.freedesktop.org/drm/intel/-/issues/3169 Signed-off-by: Lyude Paul --- drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c | 1 - 1 file changed, 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 651884390137..4f8337c7fd2e 100644 --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c @@ -646,7 +646,6 @@ int intel_dp_aux_init_backlight_funcs(struct intel_connector *connector) break; case INTEL_BACKLIGHT_DISPLAY_DDI: try_intel_interface = true; - try_vesa_interface = true; break; default: return -ENODEV; -- 2.29.2