Can the imx28 evk drive a 800x600 SVGA LCD?

[johnmu]

The imx28evk comes with a 800x480 LCD, but I would like to drive a 800x600 SVGA display.  I know the reference manual specifies 800x480 as the maximum, and I presume the limitation is the DOTCLK frequency, right?

Is this possible to do by e.g. by choosing a lower (perhaps non-standard) frame rate, thus lowering the DOTCLK frequency?  Does anyone know what the maximum DOTCLK specification is for the imx287?

[x10]

Hi, John

I have implemented 800x600 with DOTCLK=39.8MHz, and 1024x768 with DOTCLOCK=61MHz. they all work fine. The display driver includes DCP which makes display much more smoothy.

BR

Cheng Shi

[christianswion]

Hi Cheng,

i know that this is a quite old thread but your display-driver with DCP support sounds interesting to me.

I have a application with sound and display out/input and I recently ran into performance issues with the imx28.

I want to use the DCP to offload some operation from the cpu. First step would to use it in the framebuffer-driver of the imx28.

Can you provide me some information about your display-driver?

Thanks!

Christian

[johnmu]

OK, thanks.

The default 800x480 setting has a dot clock of approx 1/30 nsec = 33.3 MHz.
Frame rate = 33.3 MHz / (800+10+164+89) / (480+10+10+23) = 59.9 Hz

If you increase the resolution to 800x600, while keeping the same dot clock, the frame rate will be:
Frame rate = 33.3 MHz / (800+10+164+89) / (600+10+10+23) = 48.7 Hz

[Matteo]

Hi John,

I have a imx28evk board with a Seiko 4.3" lcd panel. I have a question about the dot clock frequency of lcd panel.

If I set for example DOTCLK_V_ACTIVE to 480,DOTCLK_V_ACTIVE to 720, .x_res to 480, .y_res to 720 and .cycle_time_ns to 37 I would expect to have a dot clock frequency of about 26.9 MHz. If I change the resolution again I would expect a different dot clock frequency insted on dot clock pin of the LCD panel I read always 25MHz.

Do you have any explanation about it?

Thanks very much!

[katte]

Yes it can and it's very simple.
You only need to change the
#define DOTCLK_V_ACTIVE 600
and
static struct mxs_platform_fb_entry fb_entry = {
.name = "43wvf1g",
.x_res = 600,
.y_res = 800,

in drivers/video/mxs/lcd_43wvf1g.c file.
I've tested it and it works.

[Matteo]

Hi Marco,

I have a imx28evk board with a Seiko 4.3" lcd panel. I have a question about the dot clock frequency of lcd panel.

If I set for example DOTCLK_V_ACTIVE to 480,DOTCLK_V_ACTIVE to 720, .x_res to 480, .y_res to 720 and .cycle_time_ns to 37 I would expect to have a dot clock frequency of about 26.9 MHz. If I change the resolution again I would expect a different dot clock frequency insted on dot clock pin of the LCD panel I read always 25MHz.

Do you have any explanation about it?

Thanks very much!

[johnmu]

Thanks, that would be most appreciated!  :-)

[x10]

I havn't found any limitation on DOTCLK, which = 432MHz / N. The definitions of related registers support higher resolution, and I will try 800x600, 1024x768 later.