How can HDMI pixclock in i.MX6 be tuned ?

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How can HDMI pixclock in i.MX6 be tuned ?

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takayayuzawa
Contributor I

How can we tune or adjust pixel clock for i.MX6 HDMI ?

Tried 2 cases in 1280x1024@60 then 9259 and 9278 pixclock periods worked.

As the driver calculated, pixclock frequency were 108.003MHz and 107.781MHz.

In actual pixclock frequency from i.MX6, 108.3MHz and 107.7MHz.

So there are some offsets between calculated pixclock frequency and actual frequency.

Just questions.

1) Is the frequency offset caused by i.MX6 hardware like PLL or clock controller inside ?

2) Can we tune or adjust the frequency into specific range like 108.003MHz ?

               /* 20 1280x1024-60 VESA */

               { NULL, 60, 1280, 1024, 9259, 248, 48, 38, 1, 112, 3,

                 FB_SYNC_HOR_HIGH_ACT | FB_SYNC_VERT_HIGH_ACT,

                 FB_VMODE_NONINTERLACED },

 

mxc_hdmi mxc_hdmi: Non-CEA mode used in HDMI mxc_hdmi mxc_hdmi: hdmi_av_composer modedb fb_var_to_videomode: ----- var -----

modedb fb_var_to_videomode: pixclock     : 9259

modedb fb_var_to_videomode: xres         : 1280

modedb fb_var_to_videomode: right_margin : 48

modedb fb_var_to_videomode: hsync_len    : 112

modedb fb_var_to_videomode: left_margin  : 248

modedb fb_var_to_videomode: yres         : 1024

modedb fb_var_to_videomode: lower_margin : 1

modedb fb_var_to_videomode: vsync_len    : 3

modedb fb_var_to_videomode: upper_margin : 38 modedb fb_var_to_videomode: ----- calculated ----- modedb fb_var_to_videomode: pixclock : 108003000

modedb fb_var_to_videomode: htotal   : 1688

modedb fb_var_to_videomode: vtotal   : 1066

modedb fb_var_to_videomode: hfreq    : 63982

modedb fb_var_to_videomode: refresh  : 60

 

               /* 20 1280x1024-60 VESA */

               { NULL, 60, 1280, 1024, 9278, 248, 48, 38, 1, 112, 3,

                 FB_SYNC_HOR_HIGH_ACT | FB_SYNC_VERT_HIGH_ACT,

                 FB_VMODE_NONINTERLACED },

 

mxc_hdmi mxc_hdmi: Non-CEA mode used in HDMI mxc_hdmi mxc_hdmi: hdmi_av_composer modedb fb_var_to_videomode: ----- var -----

modedb fb_var_to_videomode: pixclock     : 9278

modedb fb_var_to_videomode: xres         : 1280

modedb fb_var_to_videomode: right_margin : 48

modedb fb_var_to_videomode: hsync_len    : 112

modedb fb_var_to_videomode: left_margin  : 248

modedb fb_var_to_videomode: yres         : 1024

modedb fb_var_to_videomode: lower_margin : 1

modedb fb_var_to_videomode: vsync_len    : 3

modedb fb_var_to_videomode: upper_margin : 38 modedb fb_var_to_videomode: ----- calculated ----- modedb fb_var_to_videomode: pixclock : 107781000

modedb fb_var_to_videomode: htotal   : 1688

modedb fb_var_to_videomode: vtotal   : 1066

modedb fb_var_to_videomode: hfreq    : 63851

modedb fb_var_to_videomode: refresh  : 59 mxc_hdmi mxc_hdmi: final pixclk = 106165072

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igorpadykov
NXP TechSupport
NXP TechSupport

Hi takaya

i.MX6Q HDMI module conforms to CEA-861-E specification

and supported frequencies/resolutions are described in  sect.33.4.3 Supported Video Mode

https://www.nxp.com/docs/en/reference-manual/IMX6DQRM.pdf 

Operation with other frequencies/resolutions as 1280x1024 is not guaranteed

(as warned in log "Non-CEA mode used..")

Best regards
igor
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