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List:       freedesktop-xorg
Subject:    Re: 4K SMPTE Standard Outputs
From:       Ilya Anfimov <ilan () tzirechnoy ! com>
Date:       2017-07-05 8:30:48
Message-ID: 20170705083048.GA223266 () azor ! tzirechnoy ! ru
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On Tue, Jul 04, 2017 at 03:54:46PM -0400, Trevor Childs wrote:
>       I meant -- what hardware generates that signal?
> 
>    The Linux system is an Nvidia Jetson TX1 developer kit, running Ubuntu
>    16.04. The output is done over the board's HDMI (2.1, type A) port, either
>    direct into the recorder or through an AJA HA5-4K HDMI to SDI converter.

 Well, documentation said that the most default pixel clock
source for HDMI is PLL_D2, and it have precision clock stepping:
 either 38.4 MHz / DIVM * DIVN / DIVP (SDM disabled)
 or
  38.4 MHz / DIVM * (DIVN + 0.5 + SDM_DIN/8192) / DIVP
  (SDM enabled) DIVM, DIVN 8-bit, SDM_DIN 16 bit.
  I miss the point whether it is further divided by 2

  Anyway, something like SDM, M=1, N=14, SDM_DIN=7936
  (or M=1, N=28, SDM_DIN=19968) should get exactly 940 MHz pixel clock.

  So, rounding to picoseconds looks like error in NVidia kernel code,
please fix it yourself or ask them to fix it.


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