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=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 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 76E4CC49EAB for ; Mon, 28 Jun 2021 17:03:11 +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 2FE58619A0 for ; Mon, 28 Jun 2021 17:03:11 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2FE58619A0 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=tuxedocomputers.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 4584C6E4D7; Mon, 28 Jun 2021 17:03:09 +0000 (UTC) Received: from srv6.fidu.org (srv6.fidu.org [IPv6:2a01:4f8:231:de0::2]) by gabe.freedesktop.org (Postfix) with ESMTPS id 14A6D6E4D4; Mon, 28 Jun 2021 17:03:08 +0000 (UTC) Received: from localhost (localhost.localdomain [127.0.0.1]) by srv6.fidu.org (Postfix) with ESMTP id 780A7C800E0; Mon, 28 Jun 2021 19:03:06 +0200 (CEST) X-Virus-Scanned: Debian amavisd-new at srv6.fidu.org Received: from srv6.fidu.org ([127.0.0.1]) by localhost (srv6.fidu.org [127.0.0.1]) (amavisd-new, port 10024) with LMTP id s55WI_sueaYA; Mon, 28 Jun 2021 19:03:06 +0200 (CEST) Received: from [IPv6:2003:e3:7f39:4900:5a7:8b5d:f9f7:c452] (p200300E37F39490005A78B5dF9f7C452.dip0.t-ipconnect.de [IPv6:2003:e3:7f39:4900:5a7:8b5d:f9f7:c452]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) (No client certificate requested) (Authenticated sender: wse@tuxedocomputers.com) by srv6.fidu.org (Postfix) with ESMTPSA id 5D0CBC800CE; Mon, 28 Jun 2021 19:03:05 +0200 (CEST) To: harry.wentland@amd.com, sunpeng.li@amd.com, alexander.deucher@amd.com, christian.koenig@amd.com, airlied@linux.ie, daniel@ffwll.ch, maarten.lankhorst@linux.intel.com, mripard@kernel.org, tzimmermann@suse.de, jani.nikula@linux.intel.com, joonas.lahtinen@linux.intel.com, rodrigo.vivi@intel.com, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, intel-gfx@lists.freedesktop.org References: <20210618091116.14428-1-wse@tuxedocomputers.com> <20210618091116.14428-4-wse@tuxedocomputers.com> From: Werner Sembach Message-ID: <18bbd0cf-4c37-ce9d-eb63-de4131a201e1@tuxedocomputers.com> Date: Mon, 28 Jun 2021 19:03:05 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <20210618091116.14428-4-wse@tuxedocomputers.com> Content-Language: en-US Subject: Re: [Intel-gfx] [PATCH v4 03/17] drm/uAPI: Add "active bpc" as feedback channel for "max bpc" drm property 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: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" Am 18.06.21 um 11:11 schrieb Werner Sembach: > Add a new general drm property "active bpc" which can be used by graphic > drivers to report the applied bit depth per pixel back to userspace. > > While "max bpc" can be used to change the color depth, there was no way to > check which one actually got used. While in theory the driver chooses the > best/highest color depth within the max bpc setting a user might not be > fully aware what his hardware is or isn't capable off. This is meant as a > quick way to double check the setup. > > In the future, automatic color calibration for screens might also depend on > this information being available. > > Signed-off-by: Werner Sembach > --- > drivers/gpu/drm/drm_connector.c | 51 +++++++++++++++++++++++++++++++++ > include/drm/drm_connector.h | 8 ++++++ > 2 files changed, 59 insertions(+) > > diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c > index da39e7ff6965..943f6b61053b 100644 > --- a/drivers/gpu/drm/drm_connector.c > +++ b/drivers/gpu/drm/drm_connector.c > @@ -1197,6 +1197,14 @@ static const struct drm_prop_enum_list dp_colorspaces[] = { > * drm_connector_attach_max_bpc_property() to create and attach the > * property to the connector during initialization. > * > + * active bpc: > + * This read-only range property tells userspace the pixel color bit depth > + * actually used by the hardware display engine on "the cable" on a > + * connector. The chosen value depends on hardware capabilities, both > + * display engine and connected monitor, and the "max bpc" property. > + * Drivers shall use drm_connector_attach_active_bpc_property() to install > + * this property. > + * Regarding "on the cable" and dithering: As far as I can tell, what the dithering option does, is setting a hardware register here: - https://elixir.bootlin.com/linux/v5.13/source/drivers/gpu/drm/i915/display/intel_display.c#L4534 - https://elixir.bootlin.com/linux/v5.13/source/drivers/gpu/drm/i915/display/intel_display.c#L4571 So dithering seems to be calculated by fixed purpose hardware/firmware outside of the driver? The Intel driver does not seem to set a target bpc/bpp for this hardware so I guess it defaults to 6 or 8 bpc? Similar things happen on amd. Here the output dither depth seems to be written to a fixed value however: - https://elixir.bootlin.com/linux/v5.13/source/drivers/gpu/drm/amd/display/dc/dce/dce_transform.c#L828 - https://elixir.bootlin.com/linux/v5.13/source/drivers/gpu/drm/amd/display/dc/dce/dce_transform.c#L769 Does anyone know about a resource where I can read up on the used registers and what this hardware actually does? My proposal for now: "max bpc" affects what happens before dither, so I would keep "active bpc" the same and add another drm property "dither active: true/false". No additional property to control dither, as amdgpu does have one already (which isn't always active?) and Intel driver does only seem prepared for dithering at 6bpc (albeit I don't know why to dither at 6bpc and what depth to dither to?). > * Connectors also have one standardized atomic property: > * > * CRTC_ID: > @@ -2152,6 +2160,49 @@ int drm_connector_attach_max_bpc_property(struct drm_connector *connector, > } > EXPORT_SYMBOL(drm_connector_attach_max_bpc_property); > > +/** > + * drm_connector_attach_active_bpc_property - attach "active bpc" property > + * @connector: connector to attach active bpc property on. > + * @min: The minimum bit depth supported by the connector. > + * @max: The maximum bit depth supported by the connector. > + * > + * This is used to check the applied bit depth on a connector. > + * > + * Returns: > + * Zero on success, negative errno on failure. > + */ > +int drm_connector_attach_active_bpc_property(struct drm_connector *connector, int min, int max) > +{ > + struct drm_device *dev = connector->dev; > + struct drm_property *prop; > + > + if (!connector->active_bpc_property) { > + prop = drm_property_create_range(dev, DRM_MODE_PROP_IMMUTABLE, "active bpc", > + min, max); > + if (!prop) > + return -ENOMEM; > + > + connector->active_bpc_property = prop; > + drm_object_attach_property(&connector->base, prop, 0); > + } > + > + return 0; > +} > +EXPORT_SYMBOL(drm_connector_attach_active_bpc_property); > + > +/** > + * drm_connector_set_active_bpc_property - sets the active bits per color property for a connector > + * @connector: drm connector > + * @active_bpc: bits per color for the connector currently active on "the cable" > + * > + * Should be used by atomic drivers to update the active bits per color over a connector. > + */ > +void drm_connector_set_active_bpc_property(struct drm_connector *connector, int active_bpc) > +{ > + drm_object_property_set_value(&connector->base, connector->active_bpc_property, active_bpc); > +} > +EXPORT_SYMBOL(drm_connector_set_active_bpc_property); > + > /** > * drm_connector_attach_hdr_output_metadata_property - attach "HDR_OUTPUT_METADA" property > * @connector: connector to attach the property on. > diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h > index 714d1a01c065..eee86de62a5f 100644 > --- a/include/drm/drm_connector.h > +++ b/include/drm/drm_connector.h > @@ -1380,6 +1380,12 @@ struct drm_connector { > */ > struct drm_property *max_bpc_property; > > + /** > + * @active_bpc_property: Default connector property for the active bpc > + * to be driven out of the connector. > + */ > + struct drm_property *active_bpc_property; > + > #define DRM_CONNECTOR_POLL_HPD (1 << 0) > #define DRM_CONNECTOR_POLL_CONNECT (1 << 1) > #define DRM_CONNECTOR_POLL_DISCONNECT (1 << 2) > @@ -1702,6 +1708,8 @@ int drm_connector_set_panel_orientation_with_quirk( > int width, int height); > int drm_connector_attach_max_bpc_property(struct drm_connector *connector, > int min, int max); > +int drm_connector_attach_active_bpc_property(struct drm_connector *connector, int min, int max); > +void drm_connector_set_active_bpc_property(struct drm_connector *connector, int active_bpc); > > /** > * struct drm_tile_group - Tile group metadata _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx