Max Enhanced Area

Max Enhanced Area

Max Enhanced Area = MAX_ENH_SIZE_MULT x HC_WP_GRP_SIZE x HC_ERASE_GRP_SIZE x 512kBytes

Erase Unit Size = 512Kbyte × HC_ERASE_GRP_SIZE

Write protect group size = 512KB * HC_ERASE_GRP_SIZE * HC_WP_GRP_SIZE

　　　　　　　　　　   = Erase Unit Size * HC_WP_GRP_SIZE

Max Enhanced Area = MAX_ENH_SIZE_MULT * Write protect group size
　　　　　　　　     = MAX_ENH_SIZE_MULT * HC_WP_GRP_SIZE * Erase Unit Size

HC_WP_GRP_SIZE [221]
HC_ERASE_GRP_SIZE [224]

Σ Enhanced general partition Size(i) + Enhanced user data area ≤ Max Enhanced Area

Max Enhanced Area计算实例(eMMC容量32GB)：
MAX_ENH_SIZE_MULT
ecsd[157]:0xdb
ecsd[158]:0x4
ecsd[159]:0x0
==> 0x0004db

ecsd[221]:0x10
ecsd[224]:0x1

Max Enhanced Area = 0x0004db x 0x10 x 0x1 x 512kBytes
= 0x4db0 x 512kBytes
= 19888 x 0.5M
= 9944M

enhanced area需要设置如下的ext csd register：

ENH_START_ADDR，4byte，在user data area的start address

ENH_SIZE_MULT_0/1/2，3byte，在user data area的enhanced area size(mult)