From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-m15578.qiye.163.com (mail-m15578.qiye.163.com [101.71.155.78]) (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 6D7761D6BB; Mon, 29 Sep 2025 04:01:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=101.71.155.78 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759118469; cv=none; b=dkNUi9KBVqb0rVSG4HAimcvnPnC5HOpZu6SY9t716xS5qa6ND8GKfT+LbBehQgegYYANfa+8U1G6JuAelMbTwHzGFzRF7+JhH76a5Q2sgelJ7GtArEUkLMag8tz9QVmzyMDnX3wlAvp3Rr1o8bIGFc/1Nd8AH5e3j1PWlA5Xf9k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759118469; c=relaxed/simple; bh=iB15Qd/vPFDRr7h8ScCudPVdAfj6cFxz0qgU9Z9LID4=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=BSccwBMBPhy8j394oHg9vP51S5+hnekU+uoXO8Pd6hIqixll/lS+vq5Z5mJyxZjWVnFxaTJ+yRk0qAIgWMggSzBfqs5OYGcpsGpgius8tt6h+s1wpw4jkQI2ZqZ4zL6JbC/jJoZ6qAmTnlW3t8QhFT0bSRcXz2gbT7eC71ml5f4= 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=UVyf33Fq; arc=none smtp.client-ip=101.71.155.78 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="UVyf33Fq" Received: from [172.16.12.153] (unknown [58.22.7.114]) by smtp.qiye.163.com (Hmail) with ESMTP id 24652f4a9; Mon, 29 Sep 2025 11:55:46 +0800 (GMT+08:00) Message-ID: <42f41be2-9afb-4087-9ce9-1e711df98df8@rock-chips.com> Date: Mon, 29 Sep 2025 11:55:44 +0800 Precedence: bulk X-Mailing-List: linux-usb@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 5/7] drm/rockchip: cdn-dp: Add multiple bridges to support PHY port selection To: Dmitry Baryshkov Cc: Chaoyi Chen , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Vinod Koul , Kishon Vijay Abraham I , Heiko Stuebner , Sandy Huang , Andy Yan , Yubing Zhang , Frank Wang , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Amit Sunil Dhamne , Heikki Krogerus , Greg Kroah-Hartman , Dragan Simic , Johan Jonker , Diederik de Haas , Peter Robinson , linux-usb@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-phy@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-rockchip@lists.infradead.org, dri-devel@lists.freedesktop.org References: <20250922012039.323-1-kernel@airkyi.com> <20250922012039.323-6-kernel@airkyi.com> Content-Language: en-US From: Chaoyi Chen In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-HM-Tid: 0a99939cbbf503abkunmf7f47fbafa8c8 X-HM-MType: 1 X-HM-Spam-Status: e1kfGhgUHx5ZQUpXWQgPGg8OCBgUHx5ZQUlOS1dZFg8aDwILHllBWSg2Ly tZV1koWUFDSUNOT01LS0k3V1ktWUFJV1kPCRoVCBIfWUFZQ04fT1YfTkxDGBgYGBhCTx5WFRQJFh oXVRMBExYaEhckFA4PWVdZGBILWUFZTkNVSUlVTFVKSk9ZV1kWGg8SFR0UWUFZT0tIVUpLSEpPSE xVSktLVUpCS0tZBg++ DKIM-Signature: a=rsa-sha256; b=UVyf33FqlputOQa4i79XGybq+AHVBKpYG2XhkZ6ZsqEY+uBjh+doRGcpDIIyihJwJzLoZuBaP8YAxS1iEJ8+T496AL+scaEHMn+JL13fmHgyixWLNleRn15RaeUrcxUFa8lPcxDbkRBf/tFKJtLx0+uQh/Rz1zRor79EWuMmPyI=; s=default; c=relaxed/relaxed; d=rock-chips.com; v=1; bh=vM6i8BgSabuk/duHJbVX0Gnp95HLl19dL4T224ShB2g=; h=date:mime-version:subject:message-id:from; On 9/29/2025 5:27 AM, Dmitry Baryshkov wrote: > On Sun, Sep 28, 2025 at 05:52:35PM +0800, Chaoyi Chen wrote: >> On 9/23/2025 9:50 AM, Dmitry Baryshkov wrote: >> >> [...] >> >> >>>> + /* One endpoint may correspond to one HPD bridge. */ >>>> + for_each_of_graph_port_endpoint(port, dp_ep) { >>>> + /* Try to get "port" node of correspond PHY device */ >>>> + struct device_node *phy_ep __free(device_node) = >>>> + of_graph_get_remote_endpoint(dp_ep); >>>> + struct device_node *phy_port __free(device_node) = >>>> + of_get_parent(phy_ep); >>>> + >>>> + if (!phy_port) { >>>> + continue; >>>> + } >>>> + >>>> + /* >>>> + * A PHY port may contain two endpoints: USB connector port or CDN-DP port. >>>> + * Try to find the node of USB connector. >>> And then there can be a retimer between PHY and the USB-C connector. Or >>> some signal MUX. Or DP-to-HDMI bridge. Please, don't parse DT for other >>> devices. Instead you can add drm_aux_bridge to your PHY and let DRM core >>> build the bridge chain following OF graph. >>> >> I think building a bridge chain across multiple drm_aux_hpd_bridge may be difficult. First, drm_dp_hpd_bridge_register() cannot register the bridge immediately; instead, it is deferred until drm_aux_hpd_bridge_probe(). When it is added to the bridge_list, it may not yet be attached, and attempting to attach it at that point is too late. >> >> But, if I only use drm_aux_bridge on the USB-C connector, and use my own custom bridge on the PHY device and managing the alloc and attach bridge process myself, then things would become much easier. > Well... consider a your board, but add onnn,nb7vpq904m retimer between > the CDP and usb-c connector (it's not an uncommon device nowadays). Or > add fsa4480 analog audio switch. Build all the drivers as modules. You > should not need any changes to your drivers to handle such boards and > such kernel config. > > With those devices you can't handle everything inside the DP driver, > since there are two "streams" of probe events: the DRM bridge needs the > "next" bridge (in the direction from the SoC to the connector), but the > USB-C events code needs "previous" mux, switch or retirmer. After some > trial and error we have ended up with having a chain of drm_aux_bridge > devices ending up with the drm_aux_hpd_bridge inside the Type-C port > manager driver. This way the typec_* depetencies are resolved first, > going from the SoC to the Type-C controller driver then the DRM bridge > devices probe backwards, creating the chain, which is finally consumer > by the DP driver inside the SoC. Sorry, I kept trying to look for the "next bridge" in "drm_hpd_aux_bridge", and I didn't notice that "drm_aux_bridge" already had a similar implementation about "next bridge". Thanks again for your patience. BTW the devm_drm_of_get_bridge(&auxdev->dev, auxdev->dev.of_node, 0, 0) in drm_aux_bridge cannot be used directly with tcphy->dev. I may need to create a device for the dp-port child node, and then use drm_aux_bridge_register(). But this is no longer a big issue :) -- Best, Chaoyi