[PATCH] ARM: mxs/tx28: fix up LCD pads

[Shawn Guo]

On Tue, Mar 15, 2011 at 07:39:38AM +0100, Lothar Waßmann wrote:
> Hi,
> 
> Shawn Guo writes:
> > On Fri, Mar 11, 2011 at 05:16:18PM +0100, Lothar Waßmann wrote:
> > > Hi,
> > > 
> > > Shawn Guo writes:
> > > > * In any case, LCD only needs one group of VSYNC, HSYNC, and DOTCLK.
> > > >   So remove the redundant and useless one.
> > > > * LCD_ENABLE pad should not work as a GPIO for LCD, and there must be
> > > >   one pad for ENABLE function.
> > > > 
> > > > Signed-off-by: Shawn Guo <shawn.guo at freescale.com>
> > > > ---
> > > > Hi Lothar, Uwe,
> > > > 
> > > > I do not have the schematics of TX28 board, and I'm guessing the fix.
> > > > So it really needs your comments here.
> > > > 
> > > > Regards,
> > > > Shawn
> > > > 
> > > >  arch/arm/mach-mxs/mach-tx28.c |    6 +-----
> > > >  1 files changed, 1 insertions(+), 5 deletions(-)
> > > > 
> > > > diff --git a/arch/arm/mach-mxs/mach-tx28.c b/arch/arm/mach-mxs/mach-tx28.c
> > > > index b65e371..16a0059 100644
> > > > --- a/arch/arm/mach-mxs/mach-tx28.c
> > > > +++ b/arch/arm/mach-mxs/mach-tx28.c
> > > > @@ -61,11 +61,7 @@ static const iomux_cfg_t tx28_stk5v3_pads[] __initconst = {
> > > >  	MX28_PAD_LCD_RD_E__LCD_VSYNC | LCD_MODE,
> > > >  	MX28_PAD_LCD_WR_RWN__LCD_HSYNC | LCD_MODE,
> > > >  	MX28_PAD_LCD_RS__LCD_DOTCLK | LCD_MODE,
> > > > -	MX28_PAD_LCD_CS__LCD_CS | LCD_MODE,
> > > >
> > > This one is correct as it stands (i.e. the suggested change is wrong).
> > > 
> > So your panel is using LCD_CS without using LCD_RS as a couple?
> > 
> Sorry, I confused LCD_CS and LCD_ENABLE. It doesn't use LCD_CS, but
> the LCD_ENABLE function on the LCD_CS pad. Thus, the pad should be
> configured as:
> MX28_PAD_LCD_CS__LCD_ENABLE | LCD_MODE,
> 
> > > > -	MX28_PAD_LCD_VSYNC__LCD_VSYNC | LCD_MODE,
> > > > -	MX28_PAD_LCD_HSYNC__LCD_HSYNC | LCD_MODE,
> > > > -	MX28_PAD_LCD_DOTCLK__LCD_DOTCLK | LCD_MODE,
> > > >
> > > These should be removed from the pin list, as suggested.
> > > 
> > > > -	MX28_PAD_LCD_ENABLE__GPIO_1_31 | LCD_MODE,
> > > > +	MX28_PAD_LCD_CS__LCD_ENABLE | LCD_MODE,
> > > >
> > > This change is also wrong. The pad is used as a (power) enable pin for
> > > a certain family of LCDs that we recommend for use with our
> > > modules. It should be configured as GPIO and pulled high/low whenever
> > > the LCD is activated/deactivated (just like the LCD_RESET pad below).
> > > 
> > This pad is not designed for a power enable pin but DATA_ENABLE
> >
> It's also designed to be used as a GPIO, which is what we are doing.
> 
> > signal.  Why does your panel need two power enable pins here, LCD_CS
> > and LCD_RESET?
> > 
> You should ask the manufacturer of the LCD panel. As far as I can tell
> asserting LCD_RESET stops the LCD controller, while the pin connected
> to the LCD_ENABLE pad enables the backlight (which can be controlled
> further via a PWM input).
> 
It looks that we should have both lines.

MX28_PAD_LCD_CS__LCD_ENABLE | LCD_MODE,
MX28_PAD_LCD_ENABLE__GPIO_1_31 | LCD_MODE,

I was actually trying to draw attention with the patch.  Would you
mind submitting a patch (with my Reported-by or SOB) to get it fixed
properly.  After all, I do not have the board.

-- 
Regards,
Shawn