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How to config HDMI output to 1280x720@30fps?

Question asked by waley xing on Mar 4, 2018
Latest reply on Mar 9, 2018 by Joan Xie

Dear NXP,

     On I.MX6Q reference code, the HDMI output is 1920x1080@60fps or 1280x720@60fps,  but we want to support 1280x720@30fps output, I did some changes as below:

     1. u-boot parameter:

           Kernel command line: console=ttymxc0,115200 video=mxcfb0:dev=hdmi,1280x720M@30,if=RGB24,bpp=32 

     2. kernel:

             2.1  add new_mode for 1280x720@30fps output,

              static const struct fb_videomode new_mode = {
                      NULL, 30, 1280, 720, 26936, 220, 110, 20, 5, 40, 5,
                      FB_SYNC_HOR_HIGH_ACT | FB_SYNC_VERT_HIGH_ACT,
                      FB_VMODE_NONINTERLACED | FB_VMODE_ASPECT_16_9, 0
               };

             2.2  add new_mode in function mxc_hdmi_edid_rebuild_modelist() 

               fb_add_videomode(&new_mode, &hdmi->fbi->modelist);

     3. enable function dump_fb_videomode()

 

     4. kernel log:

          

mxc_hdmi 20e0000.hdmi_video: Detected HDMI controller 0x13:0xa:0xa0:0xc1
fbcvt: Refresh rate not CVT standard
fbcvt: 1280x720@30: CVT Name - Not a CVT standard - 0.921 Mega Pixel Image
fb_videomode = 29 1280 720 28368 160 32 3 8 128 5 2 0 32
Question:
       1. Why the fb_videomode is different with new_mode?
       2. Why I can't find the parameters of fb_videomode in the code?
       3. Why the HDMI display is still 60fps?
       4. How to change the code to support 1280x720@30fps?

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