topic Re: i.MX6: toggle pixel clock generation for parallel LCD in i.MX Processors

i.MX6: toggle pixel clock generation for parallel LCD

morix — Wed, 12 Jun 2019 06:26:02 GMT

Hello. I am using an i.MX6 Solo for an embedded device driving an LCD on the parallel RGB port. The device runs a Yocto-generated Linux distribution based on Linux kernel 3.10.17.

Here is the display configuration returned by command "fbset":

mode "480x272-60"
        # D: 9.000 MHz, H: 17.176 kHz, V: 60.055 Hz
        geometry 480 272 480 272 32
        timings 111111 40 2 2 2 2 10
        accel false
        rgba 8/16,8/8,8/0,8/24
endmode

Under some circumstances I would like to turn off and on the pixel clock at runtime... In other words when the device enters a "very low electromagnetic emission mode" I would like to completely turn off the pixel clock of the LCD (which causes some noise) and then I would like to turn it on again when leaving such a low emission mode... The request is to do that without restarting/rebooting the device...

Is it possible? How can I do that?

Re: i.MX6: toggle pixel clock generation for parallel LCD

jamesbone — Wed, 12 Jun 2019 14:18:34 GMT

Hello,

The device is accessed through special device nodes, usually located in the /dev directory, /dev/fb*. /dev/fb* also has several IOCTLs which act on it and through which information about the hardware can be
queried and set. The color map handling operates through IOCTLs as well. See linux/fb.h
for more information on which IOCTLs there are and which data structures they use.

Have a great day,
TIC

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