i.MX6 LVDS channels problem in 'separate' mode

[Igor]

Hi all,

I'm using a Freescale Sabre SD card with the quad-core i.MX6 processor. I want to use LVDS channels in "separate" mode.

I modified the uboot and the kernel in order to set video mode according to LVDS display panel’s spec.

UBOOT:

I properly changed the board file (in this case "board/freescale/mx6q_sabresd/mx6q_sabresd.c").

1) I added a new "fb_videomode" struct:

static struct fb_videomode lvds_wxga = {

  "WXGA", 60, 1280, 768, 14641, 40, 40, 10, 2, 80, 10,

  0,

  FB_VMODE_NONINTERLACED,

  FB_MODE_IS_DETAILED,

};

2) I modified "ipuv3_fb_init" function (called into "lcd_enable" routine):

     ret = ipuv3_fb_init(&lvds_wxga, di, IPU_PIX_FMT_RGB666, DI_PCLK_LDB, 65000000);   

3) I modified "panel_info_init":

void panel_info_init(void)

{

  panel_info.vl_bpix = LCD_BPP;

  panel_info.vl_col = lvds_wxga.xres;

  panel_info.vl_row = lvds_wxga.yres;

  panel_info.cmap = colormap;

}

KERNEL:

1) I added a video mode in struct fb_videomode in drivers/video/mxc/ldb.c according to the new LVDS display panel’s spec:

......

{

  "DS-LDB-WXGA", 60, 1280, 768, 14641,

  40, 40,

  10, 2,

  80, 10,

  0,

  FB_VMODE_NONINTERLACED,

  FB_MODE_IS_DETAILED,},

  {

.......

2) I modified struct ipuv3_fb_platform_data in arch/arm/mach-imx6/board-mx6q_sabresd.c according to new configuration:

static struct ipuv3_fb_platform_data sabresd_fb_data[] = {

  { /*fb0*/

    .disp_dev = "hdmi",

    .interface_pix_fmt  = IPU_PIX_FMT_RGB32,

    .mode_str = "1920x1080M@60",

    .default_bpp = 32,

    .int_clk = false,

    }, {

  .disp_dev = "ldb",

  .interface_pix_fmt = IPU_PIX_FMT_RGB666,

  .mode_str = "DS-LDB-WXGA",

  .default_bpp = 16,

  .int_clk = false,

  }, {

  .disp_dev = "ldb",

  .interface_pix_fmt = IPU_PIX_FMT_RGB666,

  .mode_str = "DS-LDB-WXGA",

  .default_bpp = 16,

  .int_clk = false,

  },

};

The problem is the following: both when Linux starts or when the board has finished playing a movie (using Gstreamer) on the LVDS1 channel, latter is no longer controlled (see attached file).

Using an oscilloscope I could verify that LVDS1 channel signals (Link0-, Link0+, Link1-, Link1+ etc.) disappear.

Instead LVDS0 channel works fine.

Can anyone help me figure out the exact cause of the problem?

What are the changes required to solve that issue?

Thanks a lot,

Igor

[juangutierrez · Accepted solution]

Hi

I observed that when using Display 1, the blanking signal is followed inmediatelly by an unblanking one.

The above was only true for Display 1. for display 2 the unblanking signal was never sent.

Inspecting the code I found that the unblanking message was only sent when using channel23 (MEM_BG_SYNC) which is used for background plane in display1.

So what I did was to enable the unblankig for the display 2 which uses channel 27 (MEM_DC_SYNC)

This is the patch and it seems to be working

diff --git a/drivers/media/video/mxc/output/mxc_vout.c b/drivers/media/video/mxc/output/mxc_vout.c

index ec789ec..c3ec188 100644

--- a/drivers/media/video/mxc/output/mxc_vout.c

+++ b/drivers/media/video/mxc/output/mxc_vout.c

@@ -1759,7 +1759,7 @@ static void release_disp_output(struct mxc_vout_output *vout)

        pos.y = 0;

set_window_position(vout, &pos);

-       if (get_ipu_channel(fbi) == MEM_BG_SYNC) {

+       if (get_ipu_channel(fbi) == MEM_BG_SYNC || get_ipu_channel(fbi) == MEM_DC_SYNC) {

console_lock();

fbi->fix.smem_start = vout->disp_bufs[0];

fbi->flags |= FBINFO_MISC_USEREVENT;

[LeonardoSandova]

we are currently investigating the root cause. I will post any update in this thread and also on Gstreamer and Xorg, which is another thread reporting the same issue.

Leo

[Igor]

Hi Leo. Thanks a lot.

I think there could be an issue in the function called "release_disp_output" (file: /drivers/media/video/mxc/output/mxc_vout.c).

In that function, the syncs of the screen are restored (FB_BLANK_UNBLANK) only if an IPU logical channel is set to "MEM_BG_SYNC", otherwise they are disabled (FB_BLANK_POWERDOWN).

The other problem is the screen resolution of the LVDS1 display (see the vertical bar to the right in the picture).

I think this problem is due to the bootloader: latter does not initialize the LVDS1 channel.

Unfortunately, the uboot initializes only one of the two LVDS channels (in that case LVDS0).

I can not figure out how to initialize both channels.

Do you think I should contact DENX for some advice?

Igor

[jimmychan]

For the fb0, I saw you still define it as hdmi. As you don't use the hdmi, have you try to replace it by LVDS?

[Igor]

Hi Jimmy,

Thanks for the reply!

I use hdmi channel for the desktop of Ubuntu. I'm experimenting... :smileygrin:

Igor