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

Hi,

Shawn Guo writes:

On Fri, Mar 11, 2011 at 05:16:18PM +0100, Lothar Wa?mann wrote:

quoted

Hi,

Shawn Guo writes:

quoted

* 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 <redacted>
---
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,

quoted

quoted

-	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.

quoted

-	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).


Lothar Wa?mann
-- 
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