James Cameron <qu...@laptop.org> writes: > The XO-1 SD card slot power supply circuit does not have a discharge > clamping function, and so when the firmware or software turns off the > power to the slot, the voltage falls slowly. > > The fall rate violates the specification for cards. [...] > When an SD card is used as the boot media, it remains powered, and so > one would typically not see this symptom.
I understand this is only once Linux has taken over; OFW always powers
down the card after each access?
> Open Firmware briefly powers the SD card slot during boot, as part of
> the search for an operating system to boot.
[...]
Would it be possible to avoid powering down the card after the first
power-up in OFW? Or is a "software reset" (i.e. CMD0) insufficient for
reinitialisation in Linux? (The standard suggests [2] it is, but actual
cards may or may not be behave that way.)
Would something like
' noop to card-power-off
be sufficient or does OFW rely on the card getting powered down?
I may have hit this problem again recently [1], if the SD card
containing the image to be flashed indeed gets powered down
intermittently during flashing.
Sascha
[1] message-id:toeobphnrh2....@twin.sascha.silbe.org
http://lists.laptop.org/pipermail/devel/2012-May/035137.html
[2]
https://www.sdcard.org/downloads/pls/simplified_specs/Part_1_Physical_Layer_Simplified_Specification_Ver_3.01_Final_100518.pdf
Figure 4-1, PDF page 32
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