Subject: [PATCH 4/5] fb: Add DCU framebuffer driver for Vybrid VF610 platform

From: [email-masked] (Bill Pringlemeir)
Date: Mon, 06 Jan 2014 13:50:09 -0500

> On Fri, Jul 12, 2013 at 02:07:55PM +0800, Alison Wang wrote:
>> The Display Controller Unit (DCU) module is a system master that
>> fetches graphics stored in internal or external memory and displays
>> them on a TFT LCD panel. A wide range of panel sizes is supported
>> and the timing of the interface signals is highly configurable.
>> Graphics are read directly from memory and then blended in real-time,
>> which allows for dynamic content creation with minimal CPU intervention.

On 29 Jul 2013, s.hauer at pengutronix.de wrote:

> Maybe the real question is whether we want to introduce another
> framebuffer driver at all instead of making it a DRM driver.

I didn't understand this comment at first.  I thought that the DRM
infra-structure had changed or something.  I see a recent post on
IMX-DRM and I think there is a mis-conception on the Vybrid SOC.

At first, Freescale was to incorporate a Vivante GC355 GPU for OpenVG.
However, this was removed from the design and is only present on some
'Automotive' parts, and not the VF610 nor the Tower boards.  These SOCs
only have a multi-level framebuffer with alpha blending.  Was it meant
that this be part of the DRM?  It seems that the hardware without the
'Vivante GC355 GPU' is best served by an fb driver.  Certainly, there
are very few Vybrid chips with this OpenVG on board.  I am also not
really certain what sort of user space code would use it.  Most graphics
stacks seems to want OpenGL; of course that is not a reason not to put
it in the kernel, but I don't think any Linux Vybrid devices will
actually have an OpenVG register set on board?  The majority will have
none.

Fwiw,
Bill Pringlemeir.