[U-Boot] Improper assumption of serial port

[U-Boot] Improper assumption of serial port

[Vladimir 'φ-coder/phcoder' Serbinenko]

U-boot on coreboot assumes that serial port is always available and
improperly interprets missing ones as stream of 0xff. What would be the
proper way to handle this? Is it acceptable to probe at it's address
whether we have a valid ns8250/ns16550 device (we can read back the
divisor and compare with what we have set) and dropping the serial if
none is available?

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[U-Boot] Improper assumption of serial port

[Simon Glass]

Hi Vladimir,

On Sun, Apr 7, 2013 at 8:42 AM, Vladimir '?-coder/phcoder' Serbinenko
<phcoder@gmail.com> wrote:
> U-boot on coreboot assumes that serial port is always available and
> improperly interprets missing ones as stream of 0xff. What would be the
> proper way to handle this? Is it acceptable to probe at it's address
> whether we have a valid ns8250/ns16550 device (we can read back the
> divisor and compare with what we have set) and dropping the serial if
> none is available?

Typically we can deal with this using environment variables - e.g.
stdin/stdout. However, if there is no serial port, what is the
intended console? The VGA?

I think probing is maybe acceptable. Another way might be to create a
new device tree alongside link.dts.

Regards,
Simon