[U-Boot] [resent] New chapter in i.MX51 datasheet an issue?

David Jander
2012-05-04T10:08:45Z

Hi all,

I discovered a bug in u-boot, that got evident after Freescale updated the
i.MX51 datasheets to revision 5 in March this year. I don't know if it is a
serious problem or not, but if I believe the wording of the datasheet many of
the boards that use a i.MX51 processor and running u-boot as of latest git,
can potentially suffer "permanent damage", whatever that means.

I am referring to the new paragraphs at the end of chapter 4.3.4 of the
datasheet, and the wrong interpretation of the meaning of the HVE bit in the
iomuxc.h header file of u-boot here:

arch/arm/include/asm/arch-mx5/iomux.h:

...
69 PAD_CTL_DRV_VOT_LOW = 0x0 << 13, /* Low voltage mode */
70 PAD_CTL_DRV_VOT_HIGH = 0x1 << 13,/* High voltage mode */
...

According to the reference manual, the correct meaning of this bit is negated:

"Bit 13:
High / Low Output Voltage Range. This bit selects the output voltage mode for
SD2_CMD. 0 High output voltage mode
1 Low output voltage mode"

Added to the new paragraph in the datasheet:

"The UHVIO type of I/O cells have to be configured properly according to their
supply voltage level, in order to prevent permanent damage to them and in
order to not degrade their timing performance."

Seems like we may have a problem here!

I would like to know if anyone is aware of this? Does anyone know of a board
that is actually destroyed this way?

Best regards,

--
David Jander
Protonic Holland.