[U-Boot] boot partition access at HS200 speed in eMMC

[Faiz Abbas]

Hi Everyone,

After the following patch from JJ, U-boot shifts to a lower speed mode
from HS200 when accessing a boot partition.

01298da31d mmc: Change mode when switching to a boot partition

I have looked through the JESD84-B51 spec for eMMC card and don't see it
say anywhere that boot0 partition cannot be accessed in HS200 modes.

In practice, I have seen timeouts sometimes when I try to write to the
boot partition in HS200 mode on a dra7xx-evm in U-boot but not
consistently (one would expect if such a thing was forbidden by the spec
then it wouldn't work at all).

Can anyone point to a documentation that says that boot partition cannot
be accessed in HS200 mode? Has anyone else observed failures before this
patch?

I was able to access the boot0 partition in kernel in HS200 mode (log
below). Unless there is code to fallback to a lower speed in kernel also
(which doesn't seem to be the case from a simple searching of the code),
this should prove that boot partitions can be accessed in HS200 speed mode.

Here is the log:
https://pastebin.ubuntu.com/p/W3SB4N3rfn/

Thanks,
Faiz