[...]

quoted

Also, I was giving this a second thought...

What happens with the SD 3.0 card when it *doesn't* support CMD19.
Will it still be functional afterwards or will it move from "transfer
state" to another not known state?

uffe, i am not the expert of this issue but weijun is. weijun told that
for the cards who don't support cmd19, it will take it as illegal
command and not response it. and it also sets illegal command error in
registers.
but the card status is still functional and doesn't cause unknown state.

so maybe we can just ignore the err of tuning, and use the second
patch with the refine you mentioned?

Sure, let's do that. Please send a v2 of the patchset then.

Kind regards
Uffe