Hi Russell,
On Tuesday 18 March 2014 12:56:23 Russell King - ARM Linux wrote:
On Tue, Mar 18, 2014 at 01:41:54PM +0100, Laurent Pinchart wrote:
Hi Lothar,
That's not my point. I *know* that DE is a data gating signal with a polarity already defined by the DRM_MODE_FLAG_POL_DE_(LOW|HIGH) flags. Like all other signals it gets generated on a clock edge and is sampled on a clock edge. The DRM_MODE_FLAG_POL_DE_*EDGE flags proposed above describe seem to describe just that, *not* the signal polarity. I thus want to know whether there are systems where the data signals and the DE signal need to be sampled on different edges of the pixel clock.
That's not relevant to this patch series though. This patch series is about adding configuration which will allow iMX6 SoCs to be properly configured for their displays.
iMX has the ability to:
- define the polarity of the clock signal
- define the polarity of the other signals
It does not have the ability to define which clock edge individual signals like vsync (frame clock), hsync (line clock), disable enable change on independently.
So, it doesn't make sense _here_ for the display enable to be defined by an edge - it's not something that can be changed here. What can only be changed is it's active level.
Of course, there may be some which can do this, and that's a separate problem that would need to be addressed when there's hardware that does support it.
The objection which Lothar is raising is that _this_ definition does not match the _hardware_ capabilities which it is intended to be used with, which is a very valid objection.
Thank you for the clarification. That absolutely makes sense.