[PATCH v4 0/5] simplefb: add clock handling code

Grant Likely grant.likely at linaro.org
Wed Nov 12 01:57:05 PST 2014

On Wednesday, November 12, 2014, Geert Uytterhoeven
<geert at linux-m68k.org> wrote:
> Hi Grant,
> On Tue, Nov 11, 2014 at 10:49 PM, Grant Likely <grant.likely at linaro.org> wrote:
> > However, I am concerned about handover. I've lost track over the entire
> > thread on whether the handover mechanism has been resolved, and I would
> > really like to have a proposed solution to this documented in the
> > binding. The fact that there is nothing tying the simple framebuffer to
> > the actual hardware backing the framebuffer is concerning. It means the
> > kernel needs to guess which graphics device is associated with the
> > framebuffer.
> We did discuss handover in Düsseldorf, and concluded that the simplefb's
> regs property can be used for this.
> While on a modern system with unified memory this association cannot be
> derived in a generic way, a device-specific driver for the graphics hardware
> can if the regs property of the simplefb node matches the address the CRTC
> engine is configured for.


Right, I'm going to be blunt here: That's just dumb. All the
capability needed is there in the DT to associate a simple FB to a
display controller, and the solution chosen is to use a heuristic?

The association needs to be explicit. I strongly prefer putting the
simple FB directly into the display controller node, but I would
consider phandle linkage also.


> Gr{oetje,eeting}s,
>                         Geert
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                 -- Linus Torvalds

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