From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 0598645516B for ; Sat, 3 Oct 2026 20:39:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791059979; cv=none; b=K5K/pHdP2ppxT4l0tfANtHzUvALlIZG/qjoBEN7Iex0/YsJwzBKZ5ioia6jfMXoajMDoLzFlCWi6K26EoYuH1SF3ltrVvabmn2v4JIJ6mOsFKs7j2zDpZQRUFqUWyG5lftu00zX31GkFlNiv3x9ByeGGdXpVK/MVkiZ1xejL8x0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791059979; c=relaxed/simple; bh=oq6EqG7Y5/d47J4IcDBkt55PVDMqnYeRy844W3EFL6c=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=LnbmZe5iNAYkX3BAzLuFutg3v+L946CJbt8+/temfUlcRSKXLktiT2WU9wGMUrYOuCFFrwAlY0cgVHmNSV9qT9g5k0+O87c3BAvGS7e9R67H08xxk0suMfp5m6qJKodAwNhrXK5eL1vrWZ9hWbs3XknHV/jAlXyV+6gpZzS/VSo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=noA68/7k; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="noA68/7k" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D5A7D1F0089B; Sat, 3 Oct 2026 20:39:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1791059977; bh=tSUhjkfC0Q2//h6dWhCqwgi4jeXYnkhNBRpnLdYChkc=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=noA68/7ksmbSP7UWWC0+zA5kZh994tu+Z+faRzxxNrfp0AT6nCJlGUpSNMXxx1fUP GRIbAYUlUrqClUoxTLdcx0TP8SVcfUtkH+sAaETa9Z8whx8gxSbLAjebarfJitsFJF 7XHDuUURtnQGPfZYoHN2F8p+EXF5ACwpGpguq31uHjm3yolN7WBeTPNBs3Z2NS5TNV DwJksVsvtfbsS5ObA9cWGmuGLG1RKCry+TCfkDNBR7d57lxhkrKnD6yM4B8R33rsD1 yN2OmBM2kE9RRGwbcMgGOMQzjVKgx3pCmUzyUuVqfypnWNqg8MMkoAz6dR3ba7HeVD zxLHpuf9ort0A== Date: Sat, 3 Oct 2026 22:39:34 +0200 From: Vinod Koul To: Cristian Ciocaltea Cc: Neil Armstrong , Manivannan Sadhasivam , Heiko Stuebner , Andy Yan , kernel@collabora.com, linux-phy@lists.infradead.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-rockchip@lists.infradead.org Subject: Re: [PATCH v2 1/3] phy: hdmi: Add optional FRL TxFFE config options Message-ID: References: <20260901-hdptx-ffe-v2-0-3a5922c76fc5@collabora.com> <20260901-hdptx-ffe-v2-1-3a5922c76fc5@collabora.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260901-hdptx-ffe-v2-1-3a5922c76fc5@collabora.com> On 01-09-26, 22:55, Cristian Ciocaltea wrote: > During HDMI 2.1 FRL link training, the source and sink can negotiate a > Transmitter Feed-Forward Equalization (TxFFE) level to improve the > signal quality. Starting from zero, the source may increment the TxFFE > level up to a maximum agreed during the LTS3 stage if the sink keeps > reporting FLT failures. TxFFE adjustment is optional and only attempted > when both the source and the connected sink support it. > > Since the existing HDMI PHY configuration API covers the FRL rate/lane > selection only, provide the following fields to the frl sub-struct of > phy_configure_opts_hdmi: > > * ffe_level: the TxFFE level to apply, only meaningful when > set_ffe_level is set. > > * set_ffe_level: a 1-bit flag that changes the semantics of the > phy_configure() call, i.e. when set, the PHY driver must apply the new > ffe_level and ignore the other frl related fields. The ffe_level 0 implies it is disabled, so why should we use a flag for this? Rather use if value valid (non zero) logic to apply..? > > The flag-based approach reflects an important invariant in the link > training process: whenever the FRL rate or lane count changes, the TxFFE > level must be reset to zero. A separate phy_configure() call with > set_ffe_level can only follow after the rate has been established, > making the two operations deliberately distinct. > > Signed-off-by: Cristian Ciocaltea > --- > include/linux/phy/phy-hdmi.h | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/include/linux/phy/phy-hdmi.h b/include/linux/phy/phy-hdmi.h > index d4cf4430ee8f..1d4b62475079 100644 > --- a/include/linux/phy/phy-hdmi.h > +++ b/include/linux/phy/phy-hdmi.h > @@ -19,6 +19,10 @@ enum phy_hdmi_mode { > * @tmds_char_rate: HDMI TMDS Character Rate in Hertz. > * @frl.rate_per_lane: HDMI FRL Rate per Lane in Gbps. > * @frl.lanes: HDMI FRL lanes count. > + * @frl.ffe_level: Transmitter Feed Forward Equalizer Level. > + * Optional, only meaningful when set_ffe_level flag is on. > + * @frl.set_ffe_level: Flag indicating whether or not to reconfigure ffe_level. > + * All the other struct fields must be ignored when this is used. > * > * This structure is used to represent the configuration state of a HDMI phy. > */ > @@ -29,6 +33,8 @@ struct phy_configure_opts_hdmi { > struct { > u8 rate_per_lane; > u8 lanes; > + u8 ffe_level; > + u8 set_ffe_level : 1; > } frl; > }; > }; > > -- > 2.55.0 -- ~Vinod