linux-kernel - Re: [v5 1/3] dt-bindings: msm/dsi: Add 10nm dsi phy tuning properties

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Date:   Fri, 4 Feb 2022 16:37:16 -0600
From:   Rob Herring <robh@...nel.org>
To:     Rajeev Nandan <quic_rajeevny@...cinc.com>
Cc:     dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, sean@...rly.run, daniel@...ll.ch,
        quic_abhinavk@...cinc.com, quic_kalyant@...cinc.com,
        quic_mkrishn@...cinc.com, linux-arm-msm@...r.kernel.org,
        airlied@...ux.ie, jonathan@...ek.ca, dmitry.baryshkov@...aro.org,
        swboyd@...omium.org, freedreno@...ts.freedesktop.org,
        robh+dt@...nel.org, robdclark@...il.com
Subject: Re: [v5 1/3] dt-bindings: msm/dsi: Add 10nm dsi phy tuning properties

On Mon, 31 Jan 2022 01:45:17 +0530, Rajeev Nandan wrote:
> In most cases, the default values of DSI PHY tuning registers should be
> sufficient as they are fully optimized. However, in some cases where
> extreme board parasitics cause the eye shape to degrade, the override
> bits can be used to improve the signal quality.
> 
> The general guidelines for DSI PHY tuning include:
> - High and moderate data rates may benefit from the drive strength and
>   drive level tuning.
> - Drive strength tuning will affect the output impedance and may be used
>   for matching optimization.
> - Drive level tuning will affect the output levels without affecting the
>   impedance.
> 
> The clock and data lanes have a calibration circuitry feature. The drive
> strength tuning can be done by adjusting rescode offset for hstop/hsbot,
> and the drive level tuning can be done by adjusting the LDO output level
> for the HSTX drive.
> 
> Signed-off-by: Rajeev Nandan <quic_rajeevny@...cinc.com>
> ---
> 
> Changes in v2:
>  - More details in the commit text (Stephen Boyd)
>  - Use human understandable values (Stephen Boyd, Dmitry Baryshkov)
>  - Do not take values that are going to be unused (Dmitry Baryshkov)
> 
> Changes in v3:
>  - Use "qcom," prefix (Dmitry Baryshkov)
>  - Remove encoding from phy-drive-ldo-level (Dmitry Baryshkov)
>  - Use negative values instead of two's complement (Dmitry, Rob Herring)
> 
> Changes in v4:
>  - Fix dt_binding_check error (Rob Herring's bot)
> 
> Changes in v5:
>  - None
> 
>  .../bindings/display/msm/dsi-phy-10nm.yaml         | 36 ++++++++++++++++++++++
>  1 file changed, 36 insertions(+)
> 

Reviewed-by: Rob Herring <robh@...nel.org>