Messages in this thread | | | Date | Thu, 28 Jul 2022 09:28:12 +0300 | Subject | Re: [PATCH 1/8] dt-bindings: display: ti,am65x-dss: Add port properties for DSS | From | Tomi Valkeinen <> |
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On 22/07/2022 19:16, Nishanth Menon wrote: > 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.
It doesn't require more pins. If the lowest bits are tied to ground the image is always a bit darker than it should, and you do not get the full brightness. But if you wire e.g. the red component:
SoC : Bridge R2 -> R0 R3 -> R1 R4 -> R2 R0 -> R3 R1 -> R4 R2 -> R5 R3 -> R6 R4 -> R7
or
R4 -> R0 R4 -> R1 R4 -> R2 R0 -> R3 R1 -> R4 R2 -> R5 R3 -> R6 R4 -> R7
You'll get the full range.
Tomi
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