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This adds a new option to enable the boot from eMMC
by writing to the 179 ext_csd register.

The example below shows as to enable the mmcblk0boot0
partition and also set/reset the ACK bit).

$ ./mmc bootpart enable 1 1 /dev/mmcblk0boot0
$ ./mmc extcsd read /dev/mmcblk0boot0 | grep PARTITION_CON
Boot configuration bytes [PARTITION_CONFIG: 0x49]
Reported-by: Youssef TRIKI <youssef.triki@st.com>
Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: Chris Ball <cjb@laptop.org>

This leaves "extcsd read" pointing to Giuseppe's code.  Also, abstract
out the writeprotect code so that there's only one shared implementation
in print_writeprotect_status(), used by both "extcsd read" and
"writeprotect get".
Signed-off-by: Chris Ball <cjb@laptop.org>

This patch enhances the debug information reported
for the mmc card by parsing the extended CSD registers
obviously according to all the current specifications.

I have no HW to test eMMC 4.5 at this moment. In any case,
the patch supports JEDEC Standard No. 84-B45.
No issues on JESD84-A441 and older specs raised on my side.

This patch indeed want to start providing a full parsing
of the all EXT_CSD registers in the following layout:

Name [FIELD: <value>]

Voluntarily, I added the FIELD because it can actually help on
searching though the SPEC in case of doubts.
In fact, in this stage, not all the register bits are yet parsed.
Currently this has been done for a small subset of registers
(e.g. 173, 160 ...) where IMO it's quite useful for an end-user
to get some details. I do hope this will be improved in the near
feature (also for write operations).

P.S. The original patch posted time ago for the Kernel has been
reviewed-by Sebastian Rasmussen, acked-by: Linus Walleij and reported
by Youssef Tiki.
Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: Chris Ball <cjb@laptop.org>

Signed-off-by: Chris Ball <cjb@laptop.org>

This was posted to linux-mmc@ by Johan Rudholm.
Signed-off-by: Chris Ball <cjb@laptop.org>