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omap4460 HDMI refresh rate change!

Yongmin Hou
Prodigy 55 points

Hi,

        I am using 4AI.1.4 to light up the Panda board.

        The default setting is HDMI out and the output resolution is 1280x720@60Hz.

        I want to change it to 1280x720@24Hz or 1280x720@25Hz or 1280x720@30Hz.

        I have tried to use "echo "xxxx,xxx/xx/xx/xx,xxx/xxx/xx/xx"" > /sys/devices/platform/omapdss/display1/timings.

        But it didn't work.

          Would you please tell me how to change the fresh rate of HDMI output?

        (More detail is prefer, I am newer to linux/android/omap)

           Thanks!

Vincent

  • 0
    Prodigy 55 points

    Hi All,

          I found the /driver/video/modedb.c

    /* 4: 1280x720p @ 59.94Hz/60Hz */
        {.refresh = 60, .xres = 1280, .yres = 720, .pixclock = 13468,
         .left_margin = 220, .right_margin = 110,
         .upper_margin = 20, .lower_margin = 5,
         .hsync_len = 40, .vsync_len = 5,
         .sync = FB_SYNC_HOR_HIGH_ACT | FB_SYNC_VERT_HIGH_ACT,
         .flag = FB_FLAG_RATIO_16_9,
         .vmode = FB_VMODE_NONINTERLACED},

    Should I change it to

        {.refresh = 24, .xres = 1280, .yres = 720, .pixclock = 33670,
         .left_margin = 220, .right_margin = 110,
         .upper_margin = 20, .lower_margin = 5,
         .hsync_len = 40, .vsync_len = 5,
         .sync = FB_SYNC_HOR_HIGH_ACT | FB_SYNC_VERT_HIGH_ACT,
         .flag = FB_FLAG_RATIO_16_9,
         .vmode = FB_VMODE_NONINTERLACED},

    Whether I need to modify the hwc.c to force to select this timing?

    Vincent

  • 0 in reply to Yongmin Hou
    TI__Intellectual 1300 points

    If your clock timings are correct, then there is no reason why that won't work. It would be better to add another entry to end of the table and use the hdmimode and hdmicode boot args. Basically hdmimode=1 uses the CEA table and hdmimode=0 uses the vesa table. hdmicode is the index.