APC8750 - VGA resolution

[Diego Sueiro]

Hi there,

I want to force the VGA output resolution to 640x480@60Hz.

I setup and saved the env variable wmt.display.param 7:0:24:640:480:60 on u-boot.

This works fine for kernel 2.6.31 but not for kernel 3.10.

Is there a way to accomplish this? Do I need to config the framebuffer or tweak 

something on VGA device driver?

Regards,

--
*dS
Diego Sueiro

Administrador do Portal Embarcados
www.embarcados.com.br

Engenheiro de Controle e Automação
UNIVERSIDADE FEDERAL DE ITAJUBÀ

/*long live rock 'n roll*/

[Diego Sueiro]

Folks,

Looking at the sources I believe that a have to change the wm8750-apc8750.dts file.

I've tried to just replace the 1024 and 768 for 640 and 480 values, but it did not worked.

Then I realized that another wondermedia device tree configures framebuffer for 800x480 (vt8500-bv07, wm8505-ref, wm8650-mid and wm8850-w70v2). I tried to use the same configurations for wm8750-apc8750 but the result is the same: Black screen.

I've rebuild dtb and regenerate uzImage.bin with dtb concatenated.

Any hints?

Regards,

--
*dS
Diego Sueiro

Administrador do Portal Embarcados
www.embarcados.com.br

Engenheiro de Controle e Automação
UNIVERSIDADE FEDERAL DE ITAJUBÀ

/*long live rock 'n roll*/

2013/9/2 Diego Sueiro <diego....@gmail.com>

[Diego Sueiro]

Folks,

I solved this.

On wm8750-apc8750.dts I've put:

timing0: 640x480 {

                clock-frequency = <25000000>;

                hactive = <640>;

                vactive = <480>;

                hfront-porch = <24>;

                hback-porch = <40>;

                hsync-len = <96>;

                vback-porch = <32>;

                vfront-porch = <11>;

                vsync-len = <2>;

};

But the vertical resolution is wrong. The image is not centered and is shifted.

Here is the "fbset -i" output for kernel 3.10:

mode "640x480-60"

    # D: 25.000 MHz, H: 31.250 kHz, V: 59.524 Hz

    geometry 640 480 640 960 16

    timings 40000 40 24 32 11 96 2

    rgba 5/11,6/5,5/0,0/0

endmode

And for kernel 2.6.31 (which is working fine) this is the "fbset -i" output:

mode "640x480-60"

    # D: 25.173 MHz, H: 31.466 kHz, V: 59.936 Hz

    geometry 640 480 640 480 16

    timings 39725 40 24 32 11 96 2

    rgba 5/11,6/5,5/0,0/0

endmode

What can I do to make geometry equals to "geometry 640 480 640 480 16"?

Abraços,

[Royal Panda]

Hi Diego,

I'm glad that you are working on the APC and sharing your result with us.

For your specific problem, I'm sorry, I don't have the solution. But I'm strongly recommend you the VT8500/WM8505 Linux Kernel google group : here
That is where all information are posted by the official maintainer of VIA SoC in the Mainline linux Kernel.


Let us know if you solve this.

Regards,
Panda

[Tony Prisk]

On 03/09/13 03:26, Diego Sueiro wrote:
> Folks,
>
> I solved this.
> On wm8750-apc8750.dts I've put:
>
> timing0: 640x480 {
> clock-frequency = <25000000>;
> hactive = <640>;
> vactive = <480>;
> hfront-porch = <24>;
> hback-porch = <40>;
> hsync-len = <96>;
> vback-porch = <32>;
> vfront-porch = <11>;
> vsync-len = <2>;
> };
>
>
> But the vertical resolution is wrong. The image is not centered and is
> shifted.
> Here is the "fbset -i" output for kernel 3.10:
>
> mode "640x480-60"
> # D: 25.000 MHz, H: 31.250 kHz, V: 59.524 Hz

> geometry 640 480 640 *960* 16

> timings 40000 40 24 32 11 96 2
> rgba 5/11,6/5,5/0,0/0
>
> endmode
>
>
> And for kernel 2.6.31 (which is working fine) this is the "fbset -i" output:
>
> mode "640x480-60"
> # D: 25.173 MHz, H: 31.466 kHz, V: 59.936 Hz

> geometry 640 480 640 *480* 16

> timings 39725 40 24 32 11 96 2
> rgba 5/11,6/5,5/0,0/0
> endmode
>
> What can I do to make geometry equals to "geometry 640 480 640 480 16"?
>
>
>

> Abra�os,

>
> --
> *dS
> Diego Sueiro
>
> Administrador do Portal Embarcados
> www.embarcados.com.br
>

> Engenheiro de Controle e Automa��o
> UNIVERSIDADE FEDERAL DE ITAJUB�

>
> /*long live rock 'n roll*/
>
>
> 2013/9/2 Diego Sueiro <diego....@gmail.com>
>

The first thing I notice is that you aren't requesting the same mode
that you said works on 2.6.31, so I wouldn't expect it to work correctly.

timing0: 640x480 {
clock-frequency = <25175000>;

hactive = <640>;
vactive = <480>;
hfront-porch = <24>;
hback-porch = <40>;
hsync-len = <96>;
vback-porch = <32>;
vfront-porch = <11>;
vsync-len = <2>;
};

Also, I assume you are getting y=960 because of the double-buffered
framebuffer.

Regards
Tony P

[Diego Sueiro]

Folks,

After trying some combinations the above worked for me:

display-timings {

            native-mode = <&timing0>;

            timing0: 640x480 {

                clock-frequency = <25000000>;

                hactive = <640>;

                vactive = <480>;

                hfront-porch = <24>;

                hback-porch = <110>;

                hsync-len = <96>;

                vback-porch = <32>;

                vfront-porch = <11>;

                vsync-len = <2>;

            };

};

I had to use clock-frequency = <25000000>. Putting clock-frequency = <25175000> ruffled image on display.

Instead of hback-porch = <40>, I had to use hback-porch = <110> to make image centered and not truncated.

I would like to suggest you to test this configuration and give me some feedback.

Thanks for the support.

Abraços,

--
*dS
Diego Sueiro

Administrador do Portal Embarcados
www.embarcados.com.br

Engenheiro de Controle e Automação
UNIVERSIDADE FEDERAL DE ITAJUBÀ

/*long live rock 'n roll*/

2013/9/2 Tony Prisk <li...@prisktech.co.nz>

Abraços,

--
*dS
Diego Sueiro

Administrador do Portal Embarcados
www.embarcados.com.br

Engenheiro de Controle e Automação
UNIVERSIDADE FEDERAL DE ITAJUBÀ

/*long live rock 'n roll*/


2013/9/2 Diego Sueiro <diego....@gmail.com>