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

[Faiz Abbas]

Hi,

+JJ, Jaehoon Chung

I had CCd them in my original mail but they seem to have been dropped in
the U-boot list.

On Thursday 02 August 2018 03:14 PM, Faiz Abbas wrote:
> 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
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