Hi Laurent, On Wed, Aug 23, 2017 at 12:03:32AM +0300, Laurent Pinchart wrote: > >>>>> + - phys: phandle to the external D-PHY > >>>>> + - phy-names: must contain dphy, if the implementation uses an > >>>>> + external D-PHY > >>>> > >>>> I would move the last two properties in an optional category as > >>>> they're effectively optional. I think you should also explain a bit more > >>>> clearly that the phys property must not be present if the phy-names > >>>> property is not present. > >>> > >>> It's not really optional. The IP has a configuration register that > >>> allows you to see if it's been synthesized with or without a PHY. If > >>> the right bit is set, that property will be mandatory, if not, it's > >>> useless. > >> > >> Just to confirm, the PHY is a separate IP core, right ? Is the CSI-2 > >> receiver input interface different when used with a PHY and when used > >> without one ? Could a third-party PHY be used as well ? If so, would the > >> PHY synthesis bit be set or not ? > > > > The PHY (in our case a D-PHY) is a separate entity, it can be from a 3rd > > party as the IP interface is standard, the SoC integrator would set the bit > > accordingly based on whether any PHY is present or not. There is also an > > option of routing digital output from a CSI-TX to a CSI-RX and in such case > > a PHY would not need to be used (as in the case of our current platform). > > OK, thank you for the clarification. > > Maxime mentioned that a bit can be read from a register to notify whether a > PHY has been synthesized or not. Does it influence the CSI-2 RX input > interface at all, or is the CSI-2 RX IP core synthesized the same way > regardless of whether a PHY is present or not ?
So we got an answer to this, and the physical interface remains the same. However, the PHY bit is set only when there's an internal D-PHY, which means we have basically three cases: - No D-PHY at all, D-PHY presence bit not set - Internal D-PHY, D-PHY presence bit set - External D-PHY, D-PHY presence bit not set I guess that solves our discussion about whether the phys property should be marked optional or not. It should indeed be optional, and when it's not there, the D-PHY presence bit will tell whether we have to program the internal D-PHY or not. Maxime -- Maxime Ripard, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com
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