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| author | Philip Rakity <prakity@marvell.com> | 2011-05-25 05:14:58 +0400 |
|---|---|---|
| committer | Chris Ball <cjb@laptop.org> | 2011-05-26 00:52:32 +0400 |
| commit | 08ee80cc397ac1a306ca689a22ede954d92d0db1 (patch) | |
| tree | b36819e6b52c9fd939dd6c886af734cb6ccbc45f /Documentation/ioctl | |
| parent | 4f3d3e9b50931a3ec70f324d53fb7437e2a39388 (diff) | |
| download | linux-08ee80cc397ac1a306ca689a22ede954d92d0db1.tar.xz | |
mmc: core: eMMC bus width may not work on all platforms
CMD19 -- The offical way to validate bus widths from the JEDEC spec
does not work on all platforms. Some platforms that use PCI/PCIe
to connect their SD controllers are known to fail.
If the quirk MMC_BUS_WIDTH_TEST is not defined we try to figure out
the bus width by reading the ext_csd at different bus widths and
compare this against the ext_csd read in 1 bit mode. If no ext_csd
is available we default to 1 bit operations.
Code has been tested on mmp2 against 8 bit eMMC and Transcend 2GB
card that is known to not work in 4 bit mode. The physical pins
on the card are not present to support 4 bit operation.
Signed-off-by: Philip Rakity <prakity@marvell.com>
Signed-off-by: Chris Ball <cjb@laptop.org>
Diffstat (limited to 'Documentation/ioctl')
0 files changed, 0 insertions, 0 deletions