2008-03-10 14:26:41

by Nicolas Ferre

Subject: [PATCH] atmel_lcdfb: wiring BGR to RGB color mode

Adds different wiring mode for the LCD screen.

The legacy atmel LCDC IP uses a non standard color mode,
"BGR-555.1" instead "RGB-565". The major part of graphic stacks
for embedded systems uses only "RGB-565". It is possible to swap
LCD IOs instead of doing this bit swapping by software (See
application note AT91SAM9 LCD Controller
http://www.atmel.com/dyn/resources/prod_documents/doc6300.pdf)

This wire swapping is done on the at91sam9rl-ek board (board code
using this patch will come later).
---
drivers/video/atmel_lcdfb.c | 27 ++++++++++++++++++++++-----
include/video/atmel_lcdc.h | 10 ++++++++++
2 files changed, 32 insertions(+), 5 deletions(-)

--- linux-2.6.x-rc.orig/drivers/video/atmel_lcdfb.c
+++ linux-2.6.x-rc/drivers/video/atmel_lcdfb.c
@@ -338,19 +338,35 @@ static int atmel_lcdfb_check_var(struct
break;
case 15:
case 16:
- var->red.offset = 0;
+ if (sinfo->lcd_wiring_mode == ATMEL_LCDC_WIRING_RGB) {
+ /* RGB:565 mode */
+ var->red.offset = 11;
+ var->blue.offset = 0;
+ var->green.length = 6;
+ } else {
+ /* BGR:555 mode */
+ var->red.offset = 0;
+ var->blue.offset = 10;
+ var->green.length = 5;
+ }
var->green.offset = 5;
- var->blue.offset = 10;
- var->red.length = var->green.length = var->blue.length = 5;
+ var->red.length = var->blue.length = 5;
break;
case 32:
var->transp.offset = 24;
var->transp.length = 8;
/* fall through */
case 24:
- var->red.offset = 0;
+ if (sinfo->lcd_wiring_mode == ATMEL_LCDC_WIRING_RGB) {
+ /* RGB:888 mode */
+ var->red.offset = 16;
+ var->blue.offset = 0;
+ } else {
+ /* BGR:888 mode */
+ var->red.offset = 0;
+ var->blue.offset = 16;
+ }
var->green.offset = 8;
- var->blue.offset = 16;
var->red.length = var->green.length = var->blue.length = 8;
break;
default:
@@ -697,6 +713,7 @@ static int __init atmel_lcdfb_probe(stru
sinfo->atmel_lcdfb_power_control = pdata_sinfo->atmel_lcdfb_power_control;
sinfo->guard_time = pdata_sinfo->guard_time;
sinfo->lcdcon_is_backlight = pdata_sinfo->lcdcon_is_backlight;
+ sinfo->lcd_wiring_mode = pdata_sinfo->lcd_wiring_mode;
} else {
dev_err(dev, "cannot get default configuration\n");
goto free_info;
--- linux-2.6.x-rc.orig/include/video/atmel_lcdc.h
+++ linux-2.6.x-rc/include/video/atmel_lcdc.h
@@ -22,6 +22,15 @@
#ifndef __ATMEL_LCDC_H__
#define __ATMEL_LCDC_H__

+
+/* Way LCD wires are connected to the chip:
+ * Some Atmel chips use BGR color mode (instead of standard RGB)
+ * A swapped wiring onboard can bring to RGB mode.
+ */
+#define ATMEL_LCDC_WIRING_BGR 0
+#define ATMEL_LCDC_WIRING_RGB 1
+
+
/* LCD Controller info data structure, stored in device platform_data */
struct atmel_lcdfb_info {
spinlock_t lock;
@@ -42,6 +51,7 @@ struct atmel_lcdfb_info {
u8 saved_lcdcon;

u8 default_bpp;
+ u8 lcd_wiring_mode;
unsigned int default_lcdcon2;
unsigned int default_dmacon;
void (*atmel_lcdfb_power_control)(int on);

2008-03-10 16:29:07

by Nicolas Ferre

Subject: Re: [Linux-fbdev-devel] [PATCH] atmel_lcdfb: wiring BGR to RGB colormode

Nicolas Ferre :
> Adds different wiring mode for the LCD screen.
>
> The legacy atmel LCDC IP uses a non standard color mode,
> "BGR-555.1" instead "RGB-565". The major part of graphic stacks
> for embedded systems uses only "RGB-565". It is possible to swap
> LCD IOs instead of doing this bit swapping by software (See
> application note AT91SAM9 LCD Controller
> http://www.atmel.com/dyn/resources/prod_documents/doc6300.pdf)
>
> This wire swapping is done on the at91sam9rl-ek board (board code
> using this patch will come later).

Forgotten line :

Signed-off-by: Nicolas Ferre <[email protected]>


> ---
> drivers/video/atmel_lcdfb.c | 27 ++++++++++++++++++++++-----
> include/video/atmel_lcdc.h | 10 ++++++++++
> 2 files changed, 32 insertions(+), 5 deletions(-)


--
Nicolas Ferre

2008-03-13 15:36:16

by Haavard Skinnemoen

Subject: Re: [PATCH] atmel_lcdfb: wiring BGR to RGB color mode

On Mon, 10 Mar 2008 15:26:18 +0100
Nicolas Ferre <[email protected]> wrote:

> The legacy atmel LCDC IP uses a non standard color mode,
> "BGR-555.1" instead "RGB-565". The major part of graphic stacks
> for embedded systems uses only "RGB-565". It is possible to swap
> LCD IOs instead of doing this bit swapping by software (See
> application note AT91SAM9 LCD Controller
> http://www.atmel.com/dyn/resources/prod_documents/doc6300.pdf)

> - var->red.offset = 0;
> + if (sinfo->lcd_wiring_mode == ATMEL_LCDC_WIRING_RGB) {
> + /* RGB:888 mode */
> + var->red.offset = 16;
> + var->blue.offset = 0;
> + } else {
> + /* BGR:888 mode */
> + var->red.offset = 0;
> + var->blue.offset = 16;
> + }

Does RGB:565 always imply RGB:888 and vice versa?

If not, I think it would be better with separate flags for the possible
wirings:
* 18-bit BGR-555.1 / 24-bit BGR-888
* 16-bit RGB-565
* 24-bit RGB-888

Or maybe I misunderstand something?

Haavard