Re: [PATCH v2 1/3] phy: hdmi: Add optional FRL TxFFE config options

[Vinod Koul <vkoul@kernel.org>]

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