colibri-pxa300: LCD_LDD / LCD_CS gpio conflict

[pieterg@gmx.com (pieterg)]

On Tuesday 07 September 2010 09:29:59 Eric Miao wrote:
> On Tue, Sep 7, 2010 at 3:20 PM, pieterg <pieterg@gmx.com> wrote:
> > On Tuesday 07 September 2010 04:43:31 Eric Miao wrote:
> >> On Mon, Sep 6, 2010 at 9:12 PM, pieterg <pieterg@gmx.com> wrote:
> >> > In colibri-pxa300.c, line 132, gpio config GPIO62_LCD_CS_N is
> >> > overriding the GPIO62_LCD_LDD_8 configuration, earlier in the pin
> >> > config table.
> >> >
> >> > As a result, one pixel data line is missing, obviously causing wrong
> >> > pixel data on passive lcd panels.
> >> >
> >> > Not sure what the best workaround should be.
> >> > LDD_CS is not available on the colibri evalboard as far as I can
> >> > see, so we might just define GPIO127_LCD_CS_N instead? (till the
> >> > soc/carrier board configs have been split)
> >> >
> >> > Or for now just put GPIO62_LCD_CS_N between
> >> > #ifdef ?
> >>
> >> Possibly define two groups of LCD pin configurations and select them
> >> when the appropriate LCD expansion card is plugged. If it can be
> >> detected at run-time, that will be perfect, otherwise have to come
> >> up with ugly #ifdef .. #else then.
> >
> > I don't think you can detect whether an active or passive lcd panel is
> > used. And since the LCD_CS_N is only used for active panels, we can be
> > sure that we only need it when CONFIG_FB_PXA_SMARTPANEL is defined.
> > So though it's ugly, it is already there, and we can use it.
>
> CONFIG_FB_PXA_SMARTPANEL is an inclusive config option not
> a mutual exclusive, so it's enabling a capability. Even if it's selected
> the board code can still select parallel/smartpanel protocol in the
> pxafb_mach_info.lcd_conn field. It just cannot be used safely here.

OK, I didn't realise that. In that case we cannot use it.

> If it's not run-time detectable, the ugliest way is to add a board
> specific kernel command line option, though I'd shrug.

I think a command line option is almost as ugly as a CONFIG define ;)
How about using GPIO127_LCD_CS_N instead? Then at least we won't have a 
conflict with the LDD pins.
I don't know why the conflicting GPIO62_LCD_CS_N was chosen in the first 
place?

Rgds, Pieter