tree 579e0dbd68021daee1ff0c5b400d9cdf71c6faf8
parent 4be34c99a2f3aa90fa42e62c0918f07afb8a645b
author Philip Langdale <philipl@overt.org> 1174099140 -0700
committer Pierre Ossman <drzeus@drzeus.cx> 1178021690 +0200

MMC: Fix handling of low-voltage cards

Fix handling of low voltage MMC cards.

The latest MMC and SD specs both agree that support for
low-voltage operations is indicated by bit 7 in the OCR.
The MMC spec states that the low voltage range is
1.65-1.95V while the SD spec leaves the actual voltage
range undefined - meaning that there is still no such
thing as a low voltage SD card.

However, an old Sandisk spec implied that bits 7.0
represented voltages below 2.0V in 1V or 0.5V increments,
and the code was accordingly written with that expectation.

This confusion meant that host drivers attempting to support
the typical low voltage (1.8V) would set the wrong bits in
the host OCR mask (usually bits 5 and/or 6) resulting in the
the low voltage mode never being used.

This change corrects the low voltage range and adds sanity
checks on the reserved bits (0-6) and for SD cards that
claim to support low-voltage operations.

Signed-off-by: Philip Langdale <philipl@overt.org>
Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>