* Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx> [140612 23:48]: > On Thursday 12 June 2014 22:30:44 Tony Lindgren wrote: > > > > 1. They live in separate hardware modules that can be clocked separately > > Actually I don't think that's true. The CSI2 PHY is part of the camera device, > with all its registers but the one above in the camera device register space. > For some weird reason a couple of bits were pushed to the control module, but > that doesn't make the CSI2 PHY itself a separate device. Yes they are separate. Anything in the system control module is a separate hardware module from the other devices. So in this case the CSI2 PHY is part of the system control module, not the camera module. > > 2. Doing a read-back to flush a posted write in one hardware module most > > likely won't flush the write to other and that can lead into hard to > > find mysterious bugs > > The OMAP4 ISS driver can just read back the CAMERA_RX register, can't it ? Right, but you would have to do readbacks both from the phy register and camera register to ensure writes get written. It's best to keep the logic completely separate especially considering that they can be clocked separately. > > 3. If we ever have a common system control module driver, we need to > > rewrite all the system control module register tinkering in the drivers > > Sure, but that's already the case today, as the OMAP4 ISS driver already > accesses the control module register directly. I won't make that worse :-) Well it's in staging for a reason :) > > So it's best to try to use an existing framework for it. That avoids tons of > > pain later on ;) > > I agree, but I don't think the PHY framework would be the right abstraction. > As explained above the CSI2 PHY is part of the OMAP4 ISS, so modeling its > single control module register as a PHY would be a hack. Well that register belongs to the system control module, not the camera module. It's not like the camera IO space is out of registers or something! :) We're already handling similar control module phy cases, see for example drivers/phy/phy-omap-control.c. Maybe you have most of the code already there? Regards, Tony -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
