Kernel Changes not reflecting

[Thejas K.U]

Hi.
Im Working on rockchips Firefly RK3288 reference board.I was trying to build android 5.1 from rockchip SDK. Im able to build and boot the device successfully in HDMI.But when i connect monitor to VGA im getting" input signal out of range change settings to 1366x768-60Hz "error in monitor.So i changed video mode in driver(code snippet is given below)
kernel/drivers/video/rockchip/vga/firefly_vga.c line:447

case VGA_TIMER_CHECK:

            if( vga->enable && vga_ddc_is_ok()) {

                if(ddev->ddc_check_ok == 0 && ddev->ddc_timer_start == 1) {

                    modeNum = vga_switch_default_screen();

                    ddev->ddc_check_ok = 1;

                    printk("VGA Devie connected %d\n",modeNum);

                    ddev->set_mode = 1;

                    firefly_vga_set_mode(NULL, &default_modedb[5]);/*index 5 for 1366x768@60 Hz resolution from structure 

fb_videomode sda7123_vga_mode[] : kernel/drivers/video/rockchip/vga/sda7123_vga.c */

                    printk("$CUSTOM:VGA_MODE=1366x768\n");

                    firefly_vga_enable();

                    ddev->set_mode = 0;

                }

            }

then compiled and flashed to board.But result is same and printk("$CUSTOM:VGA_MODE=1366x768\n"); is not showing at all in console.

shell@firefly:/ $ [  116.871974] vga-ddc: read and parse vga edid success.

[  116.872216] vga-ddc: max mode 1366x768@59[pixclock-85506 KHZ]

[  116.872408] vga-ddc: max mode 1366x768@59[pixclock-85506 KHZ]

[  116.872616] vga-ddc: best mode 1366x768@59[pixclock-85506 KHZ]

[  116.872755] VGA Devie connected 10

[  116.872877] firefly_vga_set_mode 203

[  116.873011] firefly_vga_set_mode 219 1920 1080 60 148500000 

[  116.873459] firefly_vga_enable 130 start

[  116.873557] firefly_switch_fb 55 

[  116.873722] switch:en=1,lcdc_id=0,screen type=1,cur type=1

[  117.070955] rk3288-lcdc lcdc0: lcdc0: dclk:148500000>>fps:60

Am i missing something ?.Insightful thoughts are appreciated.

[Thejas K.U]

 Finaly i figured out something and worked!.

Things i followed.

1.alter kernel driver.

2.build kernel

3.buid android source again     

$cd RK328_android5.1
$make -j8
$./mkimage.sh

4.flash all files to board instead of kernel alone

5.done!