From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 5C24513FD9C; Fri, 28 Jun 2024 07:37:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719560228; cv=none; b=pjvMxgZSIpcuxUAP27vQJ2+3u2/hWkYOBVIXlg1NV31XLjwPx4tYwUrsY+88DQhCjhRprMRnZ7orr9dY/hdyAidV8eOlxVn7aLQOoh7VrKpHrtY0+1FlQmI7OCUXuarXRbH8HuYx00b4ADHVE+VaYYbyXgHaZEwTT2Vd5UbXhCY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719560228; c=relaxed/simple; bh=QBlR7GnZcN6qgyINm0DiIIkviU/2h+8xXxnQLmYEisE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=VCvPZptAA9Ry07LT/hy6u0Fo9O6IoOmcPFsbltV9E47Ob9S60bQJIX+Mh1aF8IvjwmiBzr4WtBjiNwuyqIBkQUeNAQYXoSUE8dPuDYcYihL1MN0FBDJT37cJYGX//XkMXT3rNDyovelETXTxQIkY+e6iAK4UOQSo2SXi70RQXIw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=pNLGXE6U; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="pNLGXE6U" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 12186C116B1; Fri, 28 Jun 2024 07:36:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1719560227; bh=QBlR7GnZcN6qgyINm0DiIIkviU/2h+8xXxnQLmYEisE=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=pNLGXE6U0kLFod9QkUEXU+iAEhEATgeCbicetOzsLuxPiqKRsM3flHuNE07l4FaLi 02REU2ARHwm7DFLfni0+y7kf6DCLk24VoV0eovrVTTUMzsWQVPE4tVtvJuQrRoAYwW 5+HAflk1iNTq/vb8g1Sy+myH676OXoEBhQrCjigU7FxrP4pOMOMXgUU63s7IcRWLz6 5RR433E1QF7dWGQkdpoKyKr9QjlL+YmTvaLRtKiJk92I21Ug9UXEx7wx70HKl5QxNN BWikLO9NzRc0hffXIW3kFIGOhHwM+yOsCJEmfW4iARFlKC6NgWEDGnBpBREvHOUD/N qx38CWOzrNleA== Message-ID: <46d7c95f-20b0-4526-8583-1d8878afaa2f@kernel.org> Date: Fri, 28 Jun 2024 09:36:57 +0200 Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 1/2] dt-bindings: display: bridge: add TI TDP158 To: Marc Gonzalez , Conor Dooley Cc: Andrzej Hajda , Neil Armstrong , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Daniel Vetter , Liam Girdwood , Mark Brown , Rob Herring , Krzysztof Kozlowski , Conor Dooley , dri-devel@lists.freedesktop.org, devicetree@vger.kernel.org, linux-arm-msm@vger.kernel.org, Arnaud Vrac , Pierre-Hugues Husson , Dmitry Baryshkov References: <20240627-tdp158-v3-0-fb2fbc808346@freebox.fr> <20240627-tdp158-v3-1-fb2fbc808346@freebox.fr> <20240627-display-quantum-48c2fa48ed1a@spud> <2fe0c2c0-2f67-4549-b62f-3b9db005d3f7@freebox.fr> From: Krzysztof Kozlowski Content-Language: en-US Autocrypt: addr=krzk@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 27/06/2024 18:45, Marc Gonzalez wrote: > On 27/06/2024 18:25, Conor Dooley wrote: > >> On Thu, Jun 27, 2024 at 01:13:03PM +0200, Marc Gonzalez wrote: >> >>> TDP158 is an AC-coupled DVI / HDMI to TMDS level shifting Redriver. >>> It supports DVI 1.0, HDMI 1.4b and 2.0b. >>> It supports 4 TMDS channels, HPD, and a DDC interface. >>> It supports dual power supply rails (1.1V on VDD, 3.3V on VCC) >>> for power reduction. Several methods of power management are >>> implemented to reduce overall power consumption. >>> It supports fixed receiver EQ gain using I2C or pin strap to >>> compensate for different lengths input cable or board traces. >>> >>> Features >>> >>> - AC-coupled TMDS or DisplayPort dual-mode physical layer input >>> to HDMI 2.0b TMDS physical layer output supporting up to 6Gbps >>> data rate, compatible with HDMI 2.0b electrical parameters >>> - DisplayPort dual-mode standard version 1.1 >>> - Programmable fixed receiver equalizer up to 15.5dB >>> - Global or independent high speed lane control, pre-emphasis >>> and transmit swing, and slew rate control >>> - I2C or pin strap programmable >>> - Configurable as a DisplayPort redriver through I2C >>> - Full lane swap on main lanes >>> - Low power consumption (200 mW at 6Gbps, 8 mW in shutdown) >>> >>> https://www.ti.com/lit/ds/symlink/tdp158.pdf >>> >>> Signed-off-by: Marc Gonzalez >>> --- >>> .../bindings/display/bridge/ti,tdp158.yaml | 51 ++++++++++++++++++++++ >>> 1 file changed, 51 insertions(+) >>> >>> diff --git a/Documentation/devicetree/bindings/display/bridge/ti,tdp158.yaml b/Documentation/devicetree/bindings/display/bridge/ti,tdp158.yaml >>> new file mode 100644 >>> index 0000000000000..21c8585c3bb2d >>> --- /dev/null >>> +++ b/Documentation/devicetree/bindings/display/bridge/ti,tdp158.yaml >>> @@ -0,0 +1,51 @@ >>> +# SPDX-License-Identifier: GPL-2.0-only >>> +%YAML 1.2 >>> +--- >>> +$id: http://devicetree.org/schemas/display/bridge/ti,tdp158.yaml# >>> +$schema: http://devicetree.org/meta-schemas/core.yaml# >>> + >>> +title: TI TDP158 HDMI to TMDS Redriver >>> + >>> +maintainers: >>> + - Arnaud Vrac >>> + - Pierre-Hugues Husson >>> + >>> +properties: >>> + compatible: >>> + const: ti,tdp158 >>> + >>> + reg: >>> + description: I2C address of the device >> >> Is reg not required? How do you communicate with the device if the i2c >> bus is not connected? Is the enable GPIO enough to operate it in some >> situations? >> >> Otherwise this looks good to me, but given Maxime commented about the >> complexity of the device, I'm probably out of my depth! > > Valid question. > > As discussed in my brilliantly expanded commit message (:p) > the device can be configured in various ways, either through I2C registers > or by pin strap. We use the device in its default settings, so we don't > touch any I2C registers, thus I'm not sure the reg property is required. But then how would it be represented in the DT? Where / under which parent? If this is supposed to be always in I2C bus in DT, then you always need reg. If you could place it in other place, then your reasoning is valid - reg is optional. Best regards, Krzysztof