From: Vinod Koul <vkoul@kernel.org>
To: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
Cc: Neil Armstrong <neil.armstrong@linaro.org>,
Manivannan Sadhasivam <mani@kernel.org>,
Heiko Stuebner <heiko@sntech.de>,
Andy Yan <andy.yan@rock-chips.com>,
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
Date: Sun, 4 Oct 2026 12:52:07 +0200 [thread overview]
Message-ID: <asIv1zepKlIvzHX5@parshuram> (raw)
In-Reply-To: <3c0dc77b-b692-498e-aed6-aa97d827b2f4@collabora.com>
On 04-10-26, 00:33, Cristian Ciocaltea wrote:
> Hi Vinod,
>
> On 10/3/26 11:39 PM, Vinod Koul wrote:
> > 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..?
>
> That's not quite possible because level 0 is valid (and the default) according
> to HDMI 2.1 spec. The source is expected to reset TxFFE to default whenever a
> new FRL rate is set, hence the API shall be conformant.
Ah, looks like AI gave me wrong info about 0 being invalid, this is okay
then
--
~Vinod
--
linux-phy mailing list
linux-phy@lists.infradead.org
https://lists.infradead.org/mailman/listinfo/linux-phy
WARNING: multiple messages have this Message-ID (diff)
From: Vinod Koul <vkoul@kernel.org>
To: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
Cc: Neil Armstrong <neil.armstrong@linaro.org>,
Manivannan Sadhasivam <mani@kernel.org>,
Heiko Stuebner <heiko@sntech.de>,
Andy Yan <andy.yan@rock-chips.com>,
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
Date: Sun, 4 Oct 2026 12:52:07 +0200 [thread overview]
Message-ID: <asIv1zepKlIvzHX5@parshuram> (raw)
In-Reply-To: <3c0dc77b-b692-498e-aed6-aa97d827b2f4@collabora.com>
On 04-10-26, 00:33, Cristian Ciocaltea wrote:
> Hi Vinod,
>
> On 10/3/26 11:39 PM, Vinod Koul wrote:
> > 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..?
>
> That's not quite possible because level 0 is valid (and the default) according
> to HDMI 2.1 spec. The source is expected to reset TxFFE to default whenever a
> new FRL rate is set, hence the API shall be conformant.
Ah, looks like AI gave me wrong info about 0 being invalid, this is okay
then
--
~Vinod
WARNING: multiple messages have this Message-ID (diff)
From: Vinod Koul <vkoul@kernel.org>
To: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
Cc: Neil Armstrong <neil.armstrong@linaro.org>,
Manivannan Sadhasivam <mani@kernel.org>,
Heiko Stuebner <heiko@sntech.de>,
Andy Yan <andy.yan@rock-chips.com>,
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
Date: Sun, 4 Oct 2026 12:52:07 +0200 [thread overview]
Message-ID: <asIv1zepKlIvzHX5@parshuram> (raw)
In-Reply-To: <3c0dc77b-b692-498e-aed6-aa97d827b2f4@collabora.com>
On 04-10-26, 00:33, Cristian Ciocaltea wrote:
> Hi Vinod,
>
> On 10/3/26 11:39 PM, Vinod Koul wrote:
> > 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..?
>
> That's not quite possible because level 0 is valid (and the default) according
> to HDMI 2.1 spec. The source is expected to reset TxFFE to default whenever a
> new FRL rate is set, hence the API shall be conformant.
Ah, looks like AI gave me wrong info about 0 being invalid, this is okay
then
--
~Vinod
_______________________________________________
Linux-rockchip mailing list
Linux-rockchip@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-rockchip
next prev parent reply other threads:[~2026-10-04 10:52 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-01 19:55 [PATCH v2 0/3] phy: hdmi: Add FRL TxFFE level control Cristian Ciocaltea
2026-09-01 19:55 ` Cristian Ciocaltea
2026-09-01 19:55 ` Cristian Ciocaltea
2026-09-01 19:55 ` [PATCH v2 1/3] phy: hdmi: Add optional FRL TxFFE config options Cristian Ciocaltea
2026-09-01 19:55 ` Cristian Ciocaltea
2026-09-01 19:55 ` Cristian Ciocaltea
2026-10-03 20:39 ` Vinod Koul
2026-10-03 20:39 ` Vinod Koul
2026-10-03 20:39 ` Vinod Koul
2026-10-03 21:33 ` Cristian Ciocaltea
2026-10-03 21:33 ` Cristian Ciocaltea
2026-10-03 21:33 ` Cristian Ciocaltea
2026-10-04 10:52 ` Vinod Koul [this message]
2026-10-04 10:52 ` Vinod Koul
2026-10-04 10:52 ` Vinod Koul
2026-09-01 19:55 ` [PATCH v2 2/3] phy: rockchip: samsung-hdptx: Handle PHY config after module reload Cristian Ciocaltea
2026-09-01 19:55 ` Cristian Ciocaltea
2026-09-01 19:55 ` Cristian Ciocaltea
2026-09-01 20:11 ` sashiko-bot
2026-09-01 19:55 ` [PATCH v2 3/3] phy: rockchip: samsung-hdptx: Add support for FRL TxFFE level control Cristian Ciocaltea
2026-09-01 19:55 ` Cristian Ciocaltea
2026-09-01 19:55 ` Cristian Ciocaltea
2026-09-01 20:12 ` sashiko-bot
2026-10-05 10:20 ` [PATCH v2 0/3] phy: hdmi: Add " Vinod Koul
2026-10-05 10:20 ` Vinod Koul
2026-10-05 10:20 ` Vinod Koul
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