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 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 F3675CCA471 for ; Mon, 6 Oct 2025 09:23:38 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 5F2CC10E0B1; Mon, 6 Oct 2025 09:23:38 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=intel.com header.i=@intel.com header.b="I5CR3osd"; dkim-atps=neutral Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.13]) by gabe.freedesktop.org (Postfix) with ESMTPS id 097D510E0B1 for ; Mon, 6 Oct 2025 09:23:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1759742617; x=1791278617; h=date:from:to:cc:subject:message-id:references: mime-version:content-transfer-encoding:in-reply-to; bh=Ad1tQ2sZuoFqrlKSVVB0GeaSwtVymVdVil1x0KCGTM8=; b=I5CR3osdAXrISGqqROHi/n37RyChbP1NGWlD+kGZIe8l/t+ykpz07bbk T2m/ZjK1I9M1teeedD0IOiAb6igUqShwnHNsdBTFBaHqRKYbASceh/8UC PhcehMshC/qxv8nj0+Aw4y6ZhiFek5FL3cB839vr1BUSBzEmL/I6eZ8mn wZNEXIhISYm8I4kw0D4qEryLkZKCWm0UjRREHheBp4jUaGY0rj92EoAhw F5LMfZCqwf9xQpBNo1tTiT1QpypwHIknNl01iZZp3ao9AZ5nTW+P8gFdl cQO4aCQ6/UydlE+A16sczXBqAyFv7YGTE+aaomh7tJVojRrCpnj3LInfu g==; X-CSE-ConnectionGUID: /kAVE2DsTmGD4aATD5r1yA== X-CSE-MsgGUID: N0H/W8RYSm6IKIE7DZZd8A== X-IronPort-AV: E=McAfee;i="6800,10657,11573"; a="64531886" X-IronPort-AV: E=Sophos;i="6.18,319,1751266800"; d="scan'208";a="64531886" Received: from fmviesa010.fm.intel.com ([10.60.135.150]) by fmvoesa107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 06 Oct 2025 02:23:36 -0700 X-CSE-ConnectionGUID: dROji30iSOiS99xZ77D54w== X-CSE-MsgGUID: rjVlTinRRmWMFsyLCBsOLQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.18,319,1751266800"; d="scan'208";a="180635272" Received: from bergbenj-mobl1.ger.corp.intel.com (HELO localhost) ([10.245.245.80]) by fmviesa010-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 06 Oct 2025 02:23:33 -0700 Date: Mon, 6 Oct 2025 12:23:31 +0300 From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= To: Marius Vlad Cc: dri-devel@lists.freedesktop.org, dmitry.baryshkov@oss.qualcomm.com, jani.nikula@linux.intel.com, tzimmermann@suse.de, simona.vetter@ffwll.ch, derek.foreman@collabora.com, daniel.stone@collabora.com Subject: Re: [PATCH v2] drm/connector: hdmi: Add a 'link bpc' property Message-ID: References: <20251006083043.3115-1-marius.vlad@collabora.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20251006083043.3115-1-marius.vlad@collabora.com> X-Patchwork-Hint: comment Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo 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" On Mon, Oct 06, 2025 at 11:30:43AM +0300, Marius Vlad wrote: > From: Derek Foreman > > Add a way to know the actual bpc of a running link. > > Drivers might change the current bpc link value due to changes in mode > line or refresh rates. For example when enabling VRR the underlying > hardware might not be able sustain the same bandwidth for a particular > mode line, and it might attempt to lower the bpc. Not sure what this VRR stuff is trying to say. Enabling VRR doesn't itself change anything about the link bandwidth. > Another example can be > found when switching the color output format, part of YUV420 fallback. > > This means we might be displaying a stale bpc value although it was > modified for different reasons -- like a refresh rate or an output > color format. > > Introduces a new property 'link bpc' that user-space can use to get the > current bpc value of a running link while in the same time allow > user-space to set-up bpc using 'max bpc' property. > > An implementation for Weston [1] and a simple test for i-g-t [2] have been added. > > Signed-off-by: Derek Foreman > Signed-off-by: Marius Vlad > > [1] https://gitlab.freedesktop.org/wayland/weston/-/merge_requests/1850 > [2] https://lists.freedesktop.org/archives/igt-dev/2025-October/097061.html > > --- > > v1: > - https://lore.kernel.org/dri-devel/20250801101750.1726-1-marius.vlad@collabora.com/T/#u > > v2: > - replace return with EBUSY if connector already exists (Dmitry) > - add i-g-t test and an implementation for Weston (Dmitry) > - re-wording patch description (Jani) > > > drivers/gpu/drm/drm_atomic_uapi.c | 5 +++++ > drivers/gpu/drm/drm_connector.c | 25 +++++++++++++++++++++++++ > include/drm/drm_connector.h | 8 ++++++++ > 3 files changed, 38 insertions(+) > > diff --git a/drivers/gpu/drm/drm_atomic_uapi.c b/drivers/gpu/drm/drm_atomic_uapi.c > index 85dbdaa4a2e2..15c5ad7ddfb5 100644 > --- a/drivers/gpu/drm/drm_atomic_uapi.c > +++ b/drivers/gpu/drm/drm_atomic_uapi.c > @@ -776,6 +776,9 @@ static int drm_atomic_connector_set_property(struct drm_connector *connector, > fence_ptr); > } else if (property == connector->max_bpc_property) { > state->max_requested_bpc = val; > + } else if (property == connector->link_bpc_property) { > + drm_dbg_kms(dev, "only drivers can set link bpc property. Use max bpc instead\n"); > + return -EINVAL; Is there a particular reason this isn't just an immutable prop? > } else if (property == connector->privacy_screen_sw_state_property) { > state->privacy_screen_sw_state = val; > } else if (property == connector->broadcast_rgb_property) { > @@ -861,6 +864,8 @@ drm_atomic_connector_get_property(struct drm_connector *connector, > *val = 0; > } else if (property == connector->max_bpc_property) { > *val = state->max_requested_bpc; > + } else if (property == connector->link_bpc_property) { > + *val = state->hdmi.output_bpc; Assuming hdmi here doesn't seem good. What about all the other connector types? > } else if (property == connector->privacy_screen_sw_state_property) { > *val = state->privacy_screen_sw_state; > } else if (property == connector->broadcast_rgb_property) { > diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c > index 272d6254ea47..7cc99cd16e20 100644 > --- a/drivers/gpu/drm/drm_connector.c > +++ b/drivers/gpu/drm/drm_connector.c > @@ -542,6 +542,27 @@ int drmm_connector_init(struct drm_device *dev, > } > EXPORT_SYMBOL(drmm_connector_init); > > +static int > +drm_connector_attach_link_bpc_property(struct drm_connector *connector, > + int max) > +{ > + struct drm_device *dev = connector->dev; > + struct drm_property *prop; > + > + if (connector->link_bpc_property) > + return -EBUSY; > + > + prop = drm_property_create_range(dev, 0, "link bpc", 8, max); > + if (!prop) > + return -ENOMEM; > + > + connector->link_bpc_property = prop; > + > + drm_object_attach_property(&connector->base, prop, max); > + > + return 0; > +} > + > /** > * drmm_connector_hdmi_init - Init a preallocated HDMI connector > * @dev: DRM device > @@ -618,6 +639,10 @@ int drmm_connector_hdmi_init(struct drm_device *dev, > drm_connector_attach_max_bpc_property(connector, 8, max_bpc); > connector->max_bpc = max_bpc; > > + ret = drm_connector_attach_link_bpc_property(connector, max_bpc); > + if (ret) > + return ret; > + > if (max_bpc > 8) > drm_connector_attach_hdr_output_metadata_property(connector); > > diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h > index 8f34f4b8183d..4a50198aa7c0 100644 > --- a/include/drm/drm_connector.h > +++ b/include/drm/drm_connector.h > @@ -2079,6 +2079,14 @@ struct drm_connector { > */ > struct drm_property *max_bpc_property; > > + /** > + * @link_bpc_property: Current connector link bpc set by the driver > + * > + * This property can be used to retrieve the current link bpc from > + * connector_state::hdmi:output_bpc > + */ > + struct drm_property *link_bpc_property; > + > /** @privacy_screen: drm_privacy_screen for this connector, or NULL. */ > struct drm_privacy_screen *privacy_screen; > > -- > 2.47.2 -- Ville Syrjälä Intel