I have a custom board with a DVI port on it. The board has a i.MX6DL and is loosely based on the SABRE SDB. I have read in the reference manual that the HDMI PHY of the i.MX6DL is HDMI/DVI compliant and that the HDMI/DVI electrical signals are the same, so I attempted to enable "hdmi" expecting this would work for my DVI.
I have added video parameters into my boot command line as follows:
video=mxcfb0:dev=hdmi,1920x1080M@60,bpp=32
In my device tree I've added support for the framebuffer 0 device as done in the SABRESDB device trees as well:
mxcfb1: fb@0 {
compatible = "fsl,mxc_sdc_fb";
disp_dev = "hdmi";
interface_pix_fmt = "RGB24";
mode_str ="1920x1080M@60";
default_bpp = <24>;
int_clk = <0>;
late_init = <0>;
status = "okay";
};
aliases {
mxcfb0 = &mxcfb1;
};
Once these changes were in place I booted up the board, however the log was showing that the fb wasn't being created:
Error opening /dev/fb0: No such file or directory
I added in a bit more debug and found that during the probe of mxcfb0 it correctly pulls the options from the bootloader's command line, but in the "mxc_dispdrv_gethandle" function is appears to never enter the "list_for_each_entry(entry, &dispdrv_list, list)" and thus returns found=0 and the mxc display driver isn't loaded:
[ 0.234994] MIPI DSI driver module loaded
[ 0.235609] mxc_sdc_fb fb.15: mxcfb_probe enter
[ 0.235624] mxcfb_get_of_property
[ 0.235638] mxc_sdc_fb fb.15: get of property mode_str fail
[ 0.235678] fb_get_options start, : mxcfb0
[ 0.235686] fb_get_options end 0
[ 0.235704] mxcfb_option_setup end
[ 0.235711] calling mxcfb_dispdrv_init
[ 0.235716] mxcfb_dispdrv_init start
[ 0.235724] mxcfb_dispdrv_init - disp_dev: hdmi
[ 0.235733] mxcfb_dispdrv_init - mxc_dispdrv_setting - if_fmt: 910313298
[ 0.235740] mxcfb_dispdrv_init - mxc_dispdrv_setting - default_bpp: 32
[ 0.235748] mxcfb_dispdrv_init - mxc_dispdrv_setting - dft_mode_str: 1920x1080M@60
[ 0.235755] mxc_dispdrv_gethandle start
[ 0.235762] mxc_dispdrv_gethandle locked
[ 0.235781] mxc_dispdrv_gethandle unlock
[ 0.235787] mxc_dispdrv_gethandle end, found: 0
[ 0.235796] mxc_sdc_fb fb.15: NO mxc display driver found!
I checked my .config file and it appears I have framebuffer support included:
CONFIG_FB=y
Any thoughts on why this failing to enable the display driver?
Weidong,
Thanks for your input, the hdmi driver was being built it, but nothing was being registered because I was missing some elements in my device tree. I have figured that part out now, but I still have some outstanding questions if you have any input on those:
1) why is edid address 50? I pulled that from the SABRE SDB device tree but can't find any information on it
2) Where is the information about hdmi_core and hdmi_video
3) it seems that without hdmi_video installed the kernel hangs on boot up. Why is this? The other elements being removed allow it to boot correctly but /dev/fb0 simply doesn't exist, but without the video node the whole kernel fails to launch
-Mike
It turns out the mxc_dispdrv_gethandle function bombs out early because there are no drivers registered in the list, that is to say no drivers ever called mxc_dispdrv_register. The reason for *that* is because there were a few elements missing in the devicetree. In addition to the support for framebuffer0 I had to add:
&hdmi_core {
ipu_id = <0>;
disp_id = <0>;
status = "okay";
};
&hdmi_video {
fsl,phy_reg_vlev = <0x0294>;
fsl,phy_reg_cksymtx = <0x800d>;
status = "okay";
};
And also an entry in my I2C-2 bus:
hdmi: edid@50 {
compatible = "fsl,imx6-hdmi-i2c";
reg = <0x50>;
};
with all that in place I now see FB0 working. I still have some outstanding questions however about the necessity of these items.
1) why is edid address 50? I pulled that from the SABRE SDB device tree but can't find any information on it
2) Where is the information about hdmi_core and hdmi_video
3) it seems that without hdmi_video installed the kernel hangs on boot up. Why is this? The other elements being removed allow it to boot correctly but /dev/fb0 simply doesn't exist, but without the video node the whole kernel fails to launch