On Mon, Jan 15, 2024 at 08:21:42PM +0100, Bernd Edlinger wrote:

otherwise the synopsys_id value may be read out wrong,
because the GMAC_VERSION register might still be in reset
state, for at least 1 us after the reset is de-asserted.

Add a wait for 10 us before continuing to be on the safe side.

quoted

From what have you got that delay value?

Just try and error, with very old linux versions and old gcc versions
the synopsys_id was read out correctly most of the time (but not always),
with recent linux versions and recnet gcc versions it was read out
wrongly most of the time, but again not always.
I don't have access to the VHDL code in question, so I cannot
tell why it takes so long to get the correct values, I also do not
have more than a few hardware samples, so I cannot tell how long
this timeout must be in worst case.
Experimentally I can tell that the register is read several times
as zero immediately after the reset is de-asserted

Is zero a valid synopsys_id? If its not, maybe do the wait conditional
on the first read returning 0?

   Andrew