linux-kernel - Re: [PATCH 1/8] dt-bindings: display: ti,am65x-dss: Add port properties for DSS

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Message-ID: <20220722161621.p35apy5mstpgqhef@reverence>
Date:   Fri, 22 Jul 2022 11:16:21 -0500
From:   Nishanth Menon <nm@...com>
To:     Rob Herring <robh@...nel.org>
CC:     Aradhya Bhatia <a-bhatia1@...com>,
        Tomi Valkeinen <tomba@...nel.org>,
        Jyri Sarha <jyri.sarha@....fi>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Darren Etheridge <detheridge@...com>,
        Vignesh Raghavendra <vigneshr@...com>,
        Rahul T R <r-ravikumar@...com>,
        Krunal Bhargav <k-bhargav@...com>,
        Devarsh Thakkar <devarsht@...com>,
        DRI Development List <dri-devel@...ts.freedesktop.org>,
        Devicetree List <devicetree@...r.kernel.org>,
        Linux Kernel List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/8] dt-bindings: display: ti,am65x-dss: Add port
 properties for DSS

On 17:28-20220720, Rob Herring wrote:
> > On the bridge side R0->R2, G0->G1, B0->B2 would be tied to ground.
> > The bridge sees 24bits of data,  but the lsb's are always zero.
> 
> Unless the bridge ignores the LSBs, that's not the right way to do 16 to 
> 24 bit. The LSBs should be connected to the MSB of the color component 
> to get full color range.

I unfortunately cannot point specifics without violating NDAs, so
will just give a broad perspective.

Correct, this is not ideal, but in certain scenarios with limited
pins (due to iovoltage groups), we are indeed starting to see this
kind of usage model starting to pop up. Tradeoff is in a limit on
image quality, but that tends to be acceptable in certain lower cost
solutions.

-- 
Regards,
Nishanth Menon
Key (0xDDB5849D1736249D) / Fingerprint: F8A2 8693 54EB 8232 17A3  1A34 DDB5 849D 1736 249D