mmc: Optimize eMMC erase speed
Per JESD84-B51 6.6.9 Erase:
The host can erase a contiguous range of Erase Groups. Starting the erase
process is a three steps sequence. First the host defines the start address
of the range using the ERASE_GROUP_START (CMD35) command, next it defines
the last address of the range using the ERASE_GROUP_END (CMD36) command and
finally it starts the erase process by issuing the ERASE (CMD38) command
with argument bits set to zero. See Table 11 for the arguments supported by
CMD38. The address field in the erase commands is an Erase Group address,
in byte units for densities up to 2GB, and in sector units for densities
greater than 2GB. The Device will ignore all LSB's below the Erase Group
size, effectively rounding the address down to the Erase Group boundary.
So choose 2GB bytes as check condition.
If the erase size is larger that 2GB, use 2GB to avoid breaking non high
capacity cards. If erase size is less than 2GB and larger than a grp, use
'grpcnt * mmc->erase_grp_size' to cover all the sectors, else use
the number of sectors.
With test erasing 20GB eMMC
board: Evk_8ulp Evk_8mm Evk_8mn Evk_8mp Mek_8qxpc0 Mek_8qm
kingston sandisk
before: 37.683s 112.738s 129.365s 28.238s 112.605s 500.470s 490.708s
after: 0.093s 0.111s 0.951s 0.080s 0.121s 6.960s 6.915s
Tested-by: Faqiang Zhu <faqiang.zhu@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
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