[Arm-netbook] Early UART output vs. housing board discovery

Luke Kenneth Casson Leighton lkcl at lkcl.net
Wed Jan 10 11:12:24 GMT 2018

On Tue, Jan 9, 2018 at 10:22 PM, Jonathan Neuschäfer
<j.neuschaefer at gmx.net> wrote:
> Hi,
> what follows are a few questions/remarks/misunderstandings regarding the
> UART pins during early boot.
> In the EOMA68 specification, the section "Start-up procedure"[1]
> specifies that "It is required that all pins be disabled (floating
> tri-state) with the exception of the I2C Bus, the 5.0v Power and the
> Ground Pins.", which would mean that *any software* running on a CPU
> card is required to check the housing board's EEPROM before it may
> output any data on the UART, if I read it correctly.


> This would make early debugging harder, because EEPROM detection has to
> be integrated in very early code, and early code can't simply use the
> UART as an unconditional debug channel, that's guaranteed to reach the
> outside of the card, anymore.

 ok there's a difference between production and factory / testing.
factory / testing is specifically permitted to do whatever they like,
totally disregarding the EOMA68 standard IN FULL, should they choose

 it is only PRODUCTION where the EOMA68 Specification is REQUIRED -
unconditionally - to be followed.

 could i leave it with you to alter the rest of what you wrote to take
that into account before we proceed further?  also, before proceeding,
perhaps we should discuss how to make the above absolutely clear.  it
is very important that there be zero misunderstandings in the EOMA68

 thanks johnathon.


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