From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-m32117.qiye.163.com (mail-m32117.qiye.163.com [220.197.32.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D8FBA25776; Sat, 11 Oct 2025 01:09:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=220.197.32.117 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760144980; cv=none; b=MeA8hcRJa4+GFSV7gJwlCwtvW57yVmCWWcR+cf7BXARtYFyzQyjMO5MmHFlzXl7QFZhBmlqLH1AYy2x9ika4LvQuPUFs7NwjgiatFiZHepAJIX8PrD4vby4jLjFbLxR+AMblDDPDSJrhMfO08NIOI5OSp188D2rPW5ezhOO664E= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760144980; c=relaxed/simple; bh=IkBlV457elCUwnlsmaAD0xUxK5eNiGvJn1HiucN5LOU=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=GWAm9gmLLLukfUDjAzzyHXgswUbT2sqyltqeqNF9PR1qgkiedIy5NemDFGuxy05bQj7hvnj1vjAd55AH0Dq6mHa1SijUcqXk4OJTDVdJliYpnBa7VVLw//4FkTUMQbxaso6DuKuFEMu4hZYPpD4lfL9j4VebeHUvPLne8hFDFu0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=rock-chips.com; spf=pass smtp.mailfrom=rock-chips.com; dkim=pass (1024-bit key) header.d=rock-chips.com header.i=@rock-chips.com header.b=N7SbZjP3; arc=none smtp.client-ip=220.197.32.117 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=rock-chips.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=rock-chips.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=rock-chips.com header.i=@rock-chips.com header.b="N7SbZjP3" Received: from [172.16.12.26] (unknown [58.22.7.114]) by smtp.qiye.163.com (Hmail) with ESMTP id 2580dfba9; Sat, 11 Oct 2025 09:04:16 +0800 (GMT+08:00) Message-ID: <16181573-f53b-4e76-abe9-953c1e967d75@rock-chips.com> Date: Sat, 11 Oct 2025 09:04:16 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 11/18] drm/display: bridge_connector: Ensure last bridge determines EDID/modes detection capabilities To: Dmitry Baryshkov , Luca Ceresoli Cc: andrzej.hajda@intel.com, neil.armstrong@linaro.org, rfoss@kernel.org, Laurent.pinchart@ideasonboard.com, jonas@kwiboo.se, jernej.skrabec@gmail.com, maarten.lankhorst@linux.intel.com, mripard@kernel.org, tzimmermann@suse.de, airlied@gmail.com, simona@ffwll.ch, shawnguo@kernel.org, s.hauer@pengutronix.de, kernel@pengutronix.de, festevam@gmail.com, inki.dae@samsung.com, sw0312.kim@samsung.com, kyungmin.park@samsung.com, krzk@kernel.org, alim.akhtar@samsung.com, jingoohan1@gmail.com, p.zabel@pengutronix.de, hjc@rock-chips.com, heiko@sntech.de, andy.yan@rock-chips.com, dianders@chromium.org, m.szyprowski@samsung.com, jani.nikula@intel.com, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, imx@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-samsung-soc@vger.kernel.org, linux-rockchip@lists.infradead.org References: <20250930090920.131094-1-damon.ding@rock-chips.com> <20250930090920.131094-12-damon.ding@rock-chips.com> <20251001180922.6bbe42ac@booty> Content-Language: en-US From: Damon Ding In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-HM-Tid: 0a99d0cc08f803a3kunm26ee5aba1a2ddc X-HM-MType: 1 X-HM-Spam-Status: e1kfGhgUHx5ZQUpXWQgPGg8OCBgUHx5ZQUlOS1dZFg8aDwILHllBWSg2Ly tZV1koWUFDSUNOT01LS0k3V1ktWUFJV1kPCRoVCBIfWUFZGR8dSVZPThhPHRkaTx0aHklWFRQJFh oXVRMBExYaEhckFA4PWVdZGBILWUFZTkNVSUlVTFVKSk9ZV1kWGg8SFR0UWUFZT0tIVUpLSEpKQk 1VSktLVUpCWQY+ DKIM-Signature: a=rsa-sha256; b=N7SbZjP3/qQp/MbHh1FRivi1ZDZmlC1sUSNZ9BpOLHrS2WK1bnoUCFeU5/H4i5NrXj53d0oPjddq1lBuYM+9CWUWpFMHwiExq5KveU9KQo05BWcro9WNi3RFuyb3KMJi+VkkddY2/VtPvGbobSY7JZNMM8tIkSTiJqcELilOiAc=; c=relaxed/relaxed; s=default; d=rock-chips.com; v=1; bh=eV9amtj4CCoD8Gk1h+Z3/oynWPk9WjFeER7mS5pHxCc=; h=date:mime-version:subject:message-id:from; Hi, On 10/10/2025 10:02 PM, Dmitry Baryshkov wrote: > On Thu, Oct 09, 2025 at 12:10:42PM +0800, Damon Ding wrote: >> Hi Luca, >> >> On 10/2/2025 12:09 AM, Luca Ceresoli wrote: >>> Hello Damon, >>> >>> On Tue, 30 Sep 2025 17:09:13 +0800 >>> Damon Ding wrote: >>> >>>> When multiple bridges are present, EDID detection capability >>>> (DRM_BRIDGE_OP_EDID) takes precedence over modes detection >>>> (DRM_BRIDGE_OP_MODES). To ensure the above two capabilities are >>>> determined by the last bridge in the chain, we handle three cases: >>>> >>>> Case 1: The later bridge declares only DRM_BRIDGE_OP_MODES >>>> - If the previous bridge declares DRM_BRIDGE_OP_EDID, set >>>> &drm_bridge_connector.bridge_edid to NULL and set >>>> &drm_bridge_connector.bridge_modes to the later bridge. >>>> - Ensure modes detection capability of the later bridge will not >>>> be ignored. >>>> >>>> Case 2: The later bridge declares only DRM_BRIDGE_OP_EDID >>>> - If the previous bridge declares DRM_BRIDGE_OP_MODES, set >>>> &drm_bridge_connector.bridge_modes to NULL and set >>>> &drm_bridge_connector.bridge_edid to the later bridge. >>>> - Although EDID detection capability has higher priority, this >>>> operation is for balance and makes sense. >>>> >>>> Case 3: the later bridge declares both of them >>>> - Assign later bridge as &drm_bridge_connector.bridge_edid and >>>> and &drm_bridge_connector.bridge_modes to this bridge. >>>> - Just leave transfer of these two capabilities as before. >>> >>> I think the whole explanation can be more concisely rewritten as: >>> >>> If the later bridge declares OP_EDID, OP_MODES or both, then both >>> .bridge_modes and .bridge_edid should be set to NULL (if any was set >>> from a previous bridge), and then .bridge_modes and/or .bridge_edid be >>> set to the later bridge as is done already. >>> >>> Does this look correct (i.e. does it convey the same meaning)? >>> >>>> --- a/drivers/gpu/drm/display/drm_bridge_connector.c >>>> +++ b/drivers/gpu/drm/display/drm_bridge_connector.c >>>> @@ -640,6 +640,7 @@ struct drm_connector *drm_bridge_connector_init(struct drm_device *drm, >>>> struct drm_connector *connector; >>>> struct i2c_adapter *ddc = NULL; >>>> struct drm_bridge *bridge, *panel_bridge = NULL; >>>> + struct drm_bridge *pre_bridge_edid, *pre_bridge_modes; >>>> unsigned int supported_formats = BIT(HDMI_COLORSPACE_RGB); >>>> unsigned int max_bpc = 8; >>>> bool support_hdcp = false; >>>> @@ -668,6 +669,9 @@ struct drm_connector *drm_bridge_connector_init(struct drm_device *drm, >>>> */ >>>> connector_type = DRM_MODE_CONNECTOR_Unknown; >>>> drm_for_each_bridge_in_chain(encoder, bridge) { >>>> + pre_bridge_edid = bridge_connector->bridge_edid; >>>> + pre_bridge_modes = bridge_connector->bridge_modes; >>>> + >>>> if (!bridge->interlace_allowed) >>>> connector->interlace_allowed = false; >>>> if (!bridge->ycbcr_420_allowed) >>>> @@ -681,6 +685,44 @@ struct drm_connector *drm_bridge_connector_init(struct drm_device *drm, >>>> bridge_connector->bridge_detect = bridge; >>>> if (bridge->ops & DRM_BRIDGE_OP_MODES) >>>> bridge_connector->bridge_modes = bridge; >>>> + >>>> + /* >>>> + * When multiple bridges are present, EDID detection capability >>>> + * (DRM_BRIDGE_OP_EDID) takes precedence over modes detection >>>> + * (DRM_BRIDGE_OP_MODES). To ensure the above two capabilities >>>> + * are determined by the last bridge in the chain, we handle >>>> + * three cases: >>>> + * >>>> + * Case 1: The later bridge declares only DRM_BRIDGE_OP_MODES >>>> + * - If the previous bridge declares DRM_BRIDGE_OP_EDID, set >>>> + * &drm_bridge_connector.bridge_edid to NULL and set >>>> + * &drm_bridge_connector.bridge_modes to the later bridge. >>>> + * - Ensure modes detection capability of the later bridge >>>> + * will not be ignored. >>>> + * >>>> + * Case 2: The later bridge declares only DRM_BRIDGE_OP_EDID >>>> + * - If the previous bridge declares DRM_BRIDGE_OP_MODES, set >>>> + * &drm_bridge_connector.bridge_modes to NULL and set >>>> + * &drm_bridge_connector.bridge_edid to the later bridge. >>>> + * - Although EDID detection capability has higher priority, >>>> + * this operation is for balance and makes sense. >>>> + * >>>> + * Case 3: the later bridge declares both of them >>>> + * - Assign later bridge as &drm_bridge_connector.bridge_edid >>>> + * and &drm_bridge_connector.bridge_modes to this bridge. >>>> + * - Just leave transfer of these two capabilities as before. >>>> + */ >>>> + if (bridge->ops & DRM_BRIDGE_OP_EDID && >>>> + !(bridge->ops & DRM_BRIDGE_OP_MODES)) { >>>> + if (pre_bridge_modes) >>>> + bridge_connector->bridge_modes = NULL; >>>> + } >>>> + if (bridge->ops & DRM_BRIDGE_OP_MODES && >>>> + !(bridge->ops & DRM_BRIDGE_OP_EDID)) { >>>> + if (pre_bridge_edid) >>>> + bridge_connector->bridge_edid = NULL; >>>> + } >>>> + >>> >>> If the above rewrite is correct, then I think this patch can be >>> rewritten in a simple way (build tested only): >>> >>> diff --git a/drivers/gpu/drm/display/drm_bridge_connector.c b/drivers/gpu/drm/display/drm_bridge_connector.c >>> index a5bdd6c10643..bd5dbafe88bc 100644 >>> --- a/drivers/gpu/drm/display/drm_bridge_connector.c >>> +++ b/drivers/gpu/drm/display/drm_bridge_connector.c >>> @@ -672,14 +672,18 @@ struct drm_connector *drm_bridge_connector_init(struct drm_device *drm, >>> if (!bridge->ycbcr_420_allowed) >>> connector->ycbcr_420_allowed = false; >>> - if (bridge->ops & DRM_BRIDGE_OP_EDID) >>> - bridge_connector->bridge_edid = bridge; >>> + if (bridge->ops & DRM_BRIDGE_OP_EDID || bridge->ops & DRM_BRIDGE_OP_MODES) { >>> + bridge_connector->bridge_edid = NULL; >>> + bridge_connector->bridge_modes = NULL; >>> + if (bridge->ops & DRM_BRIDGE_OP_EDID) >>> + bridge_connector->bridge_edid = bridge; >>> + if (bridge->ops & DRM_BRIDGE_OP_MODES) >>> + bridge_connector->bridge_modes = bridge; >>> + } >>> if (bridge->ops & DRM_BRIDGE_OP_HPD) >>> bridge_connector->bridge_hpd = bridge; >>> if (bridge->ops & DRM_BRIDGE_OP_DETECT) >>> bridge_connector->bridge_detect = bridge; >>> - if (bridge->ops & DRM_BRIDGE_OP_MODES) >>> - bridge_connector->bridge_modes = bridge; >>> if (bridge->ops & DRM_BRIDGE_OP_HDMI) { >>> if (bridge_connector->bridge_hdmi) >>> return ERR_PTR(-EBUSY); >>> >> >> Yes, this is correct and maintains functional equivalence with the previous >> implementation. >> >> I previously attempted to implement this feature by modifying the logic in >> this section. However, that approach would obscure the explicit propagation >> semantics of the bridge chain flags (OP_EDID/OP_HPD/OP_DETECT/OP_MODES). >> Therefore, I finally decided to implemented it as a specific check after >> this code block. >> >> Dmitry, what's your take on this? > > I think I prefer Luca's code, it is simpler and easier to understand. It > doesn't need a huge comment, something like "leave the last bridge which > provides either OP_EDID or OP_MODES" should be enough. > Yes, I will update the code in v7. >> >>> Another thing to note is that this patch conflicts with [0], which I >>> plan to apply in the next few days. The two patches are orthogonal but >>> they insist on the same lines (those assigning >>> bridge_connector->bridge_* = bridge). Not a big deal, whichever patch >>> comes later will be easily adapted. Just wanted to ensure you are aware. >>> >>> [0] https://lore.kernel.org/all/20250926-drm-bridge-alloc-getput-bridge-connector-v2-1-138b4bb70576@bootlin.com/ >>> >> >> This is indeed a clever approach to the managing bridge resource cleanup in >> drm_bridge_connector. Thanks a lot for the heads-up! I'll resolve this >> conflict and rebase the patch series. >> >> Apologies for the delayed reply as I was on vacation. ;-) Best regards, Damon