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=-8.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED 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 D44FBC433E0 for ; Thu, 14 Jan 2021 07:12:26 +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 92B092395C for ; Thu, 14 Jan 2021 07:12:26 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 92B092395C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=intel-gfx-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 6815D89CF7; Thu, 14 Jan 2021 07:12:21 +0000 (UTC) Received: from mga04.intel.com (mga04.intel.com [192.55.52.120]) by gabe.freedesktop.org (Postfix) with ESMTPS id A14FD89829; Thu, 14 Jan 2021 07:12:19 +0000 (UTC) IronPort-SDR: JBtT5Cu4ezGkT0sibzYWKHVHbbw5b+4tOO6fXsuJq7U1+cO/5nSDwfWM5vdsvVtkiNAYnJ2aZt OGPgZPsBLEvQ== X-IronPort-AV: E=McAfee;i="6000,8403,9863"; a="175740344" X-IronPort-AV: E=Sophos;i="5.79,346,1602572400"; d="scan'208";a="175740344" Received: from orsmga002.jf.intel.com ([10.7.209.21]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Jan 2021 23:12:18 -0800 IronPort-SDR: cJDv/L0tfPx9bJ4fkZ1bsmZhxw7AiOgksUX2g5eH3BzEnvhub4FHEwNlujc4FtO8Vd2BOnWG/l sxsVVmHUs+gg== X-IronPort-AV: E=Sophos;i="5.79,346,1602572400"; d="scan'208";a="364136636" Received: from dforourk-mobl1.ger.corp.intel.com (HELO localhost) ([10.213.254.146]) by orsmga002-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Jan 2021 23:12:11 -0800 From: Jani Nikula To: Lyude Paul , dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org In-Reply-To: <20210113235426.2190684-2-lyude@redhat.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo References: <20210113235426.2190684-1-lyude@redhat.com> <20210113235426.2190684-2-lyude@redhat.com> Date: Thu, 14 Jan 2021 09:12:08 +0200 Message-ID: <871reornzr.fsf@intel.com> MIME-Version: 1.0 Subject: Re: [Intel-gfx] [PATCH v6 1/4] drm/i915: Keep track of pwm-related backlight hooks separately X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Arnd Bergmann , David Airlie , Lucas De Marchi , open list , Chris Wilson , Vasily Khoruzhick , Dave Airlie Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" On Wed, 13 Jan 2021, Lyude Paul wrote: > Currently, every different type of backlight hook that i915 supports is > pretty straight forward - you have a backlight, probably through PWM > (but maybe DPCD), with a single set of platform-specific hooks that are > used for controlling it. > > HDR backlights, in particular VESA and Intel's HDR backlight > implementations, can end up being more complicated. With Intel's > proprietary interface, HDR backlight controls always run through the > DPCD. When the backlight is in SDR backlight mode however, the driver > may need to bypass the TCON and control the backlight directly through > PWM. > > So, in order to support this we'll need to split our backlight callbacks > into two groups: a set of high-level backlight control callbacks in > intel_panel, and an additional set of pwm-specific backlight control > callbacks. This also implies a functional changes for how these > callbacks are used: > > * We now keep track of two separate backlight level ranges, one for the > high-level backlight, and one for the pwm backlight range > * We also keep track of backlight enablement and PWM backlight > enablement separately > * Since the currently set backlight level might not be the same as the > currently programmed PWM backlight level, we stop setting > panel->backlight.level with the currently programmed PWM backlight > level in panel->backlight.pwm_funcs->setup(). Instead, we rely > on the higher level backlight control functions to retrieve the > current PWM backlight level (in this case, intel_pwm_get_backlight()). > Note that there are still a few PWM backlight setup callbacks that > do actually need to retrieve the current PWM backlight level, although > we no longer save this value in panel->backlight.level like before. > > Additionally, we drop the call to lpt_get_backlight() in > lpt_setup_backlight(), and avoid unconditionally writing the PWM value that > we get from it and only write it back if we're in CPU mode, and switching > to PCH mode. The reason for this is because in the original codepath for > this, it was expected that the intel_panel_bl_funcs->setup() hook would be > responsible for fetching the initial backlight level. On lpt systems, the > only time we could ever be in PCH backlight mode is during the initial > driver load - meaning that outside of the setup() hook, lpt_get_backlight() > will always be the callback used for retrieving the current backlight > level. After this patch we still need to fetch and write-back the PCH > backlight value if we're switching from CPU mode to PCH, but because > intel_pwm_setup_backlight() will retrieve the backlight level after setup() > using the get() hook, which always ends up being lpt_get_backlight(). Thus > - an additional call to lpt_get_backlight() in lpt_setup_backlight() is > made redundant. > > v7: > * Use panel->backlight.pwm_funcs->get() to get the backlight level in > intel_pwm_setup_backlight(), lest we upset lockdep I think this change is wrong, as it now bypasses intel_panel_invert_pwm_level(). Please explain. I don't see anything in there that could trigger a lockdep warning. Perhaps it's the below you're referring to, but I think the root cause is different? > @@ -1788,22 +1780,17 @@ static int vlv_setup_backlight(struct intel_connector *connector, enum pipe pipe > panel->backlight.active_low_pwm = ctl2 & BLM_POLARITY_I965; > > ctl = intel_de_read(dev_priv, VLV_BLC_PWM_CTL(pipe)); > - panel->backlight.max = ctl >> 16; > + panel->backlight.pwm_level_max = ctl >> 16; > > - if (!panel->backlight.max) > - panel->backlight.max = get_backlight_max_vbt(connector); > + if (!panel->backlight.pwm_level_max) > + panel->backlight.pwm_level_max = get_backlight_max_vbt(connector); > > - if (!panel->backlight.max) > + if (!panel->backlight.pwm_level_max) > return -ENODEV; > > - panel->backlight.min = get_backlight_min_vbt(connector); > + panel->backlight.pwm_level_min = get_backlight_min_vbt(connector); > > - val = _vlv_get_backlight(dev_priv, pipe); Turns out this is a meaningful change, as the higher level vlv_get_backlight() function that will be called instead hits: <4>[ 12.870202] i915 0000:00:02.0: drm_WARN_ON(!drm_modeset_is_locked(&dev->mode_config.connection_mutex)) in intel_connector_get_pipe(connector). It's a real problem. See this, it's obvious (in retrospect): https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_19348/fi-bsw-kefka/igt@runner@aborted.html https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_19348/fi-bsw-kefka/boot0.txt I don't have a quick answer how this could be handled neatly. Perhaps the ->get call (or rather, intel_pwm_get_backlight) to set panel->backlight.level needs to be spread out to the end of each pwm_funcs->setup function after all? Though it's at the wrong abstraction level wrt level being a higher level, uh, level. I don't think it's enough to just grab connection_mutex around setup (and even checking if we can do that is a bunch of digging) - I think it's likely intel_connector_get_pipe() returns INVALID_PIPE at that point. Okay, here's a clumsy suggestion that I think works around this and unblocks the series until we figure out a better way: 1. At the end of vlv_setup_backlight(): /* add fixme comment about how wrong this is */ panel->backlight.level = intel_panel_invert_pwm_level(connector, _vlv_get_backlight()); 2. In intel_pwm_setup_backlight() only set level if ->setup didn't: if (!panel->backlight.level) panel->backlight.level = intel_pwm_get_backlight(connector); What do you think? BR, Jani. > - val = intel_panel_compute_brightness(connector, val); > - panel->backlight.level = clamp(val, panel->backlight.min, > - panel->backlight.max); > - > - panel->backlight.enabled = ctl2 & BLM_PWM_ENABLE; > + panel->backlight.pwm_enabled = ctl2 & BLM_PWM_ENABLE; > > return 0; > } > @@ -1828,24 +1815,18 @@ bxt_setup_backlight(struct intel_connector *connector, enum pipe unused) -- Jani Nikula, Intel Open Source Graphics Center _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx