mmc: export eMMC4.4 enhanced area details to sysfs

Enhanced area feature is a new feature defined in eMMC4.4 standard. This
user data area provides higher performance/reliability, at the expense
of using twice the effective media space due to the area using SLC.

The MMC driver now reads out the enhanced area offset and size and adds
them to the device attributes in sysfs. Enabling the enhanced area can
only be done once, and should be done in manufacturing. To use this
feature, bit ERASE_GRP_DEF should also be set.

Documentation/ABI/testing/sysfs-devices-mmc describes the two new
attributes.

Signed-off-by: Chuanxiao Dong <chuanxiao.dong@intel.com>
Reviewed-by: Chris Ball <cjb@laptop.org>
Signed-off-by: Chris Ball <cjb@laptop.org>

1 files changed, 21 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-devices-mmc b/Documentation/ABI/testing/sysfs-devices-mmc
new file mode 100644
index 000000000000..5a50ab655843
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-devices-mmc
@@ -0,0 +1,21 @@
+What:           /sys/devices/.../mmc_host/mmcX/mmcX:XXXX/enhanced_area_offset
+Date:           January 2011
+Contact:        Chuanxiao Dong <chuanxiao.dong@intel.com>
+Description:
+                Enhanced area is a new feature defined in eMMC4.4 standard.
+                eMMC4.4 or later card can support such feature. This kind of
+                area can help to improve the card performance. If the feature
+                is enabled, this attribute will indicate the start address of
+                enhanced data area. If not, this attribute will be -EINVAL.
+                Unit Byte. Format decimal.
+
+What:           /sys/devices/.../mmc_host/mmcX/mmcX:XXXX/enhanced_area_size
+Date:           January 2011
+Contact:        Chuanxiao Dong <chuanxiao.dong@intel.com>
+Description:
+                Enhanced area is a new feature defined in eMMC4.4 standard.
+                eMMC4.4 or later card can support such feature. This kind of
+                area can help to improve the card performance. If the feature
+                is enabled, this attribute will indicate the size of enhanced
+                data area. If not, this attribute will be -EINVAL.
+                Unit KByte. Format decimal.