After re-flashing the ROM of my Lenovo s650, that is the message after rebooting my smartphone. - "tool dl image fail, uboot is blocked by dl info" To fix the issue, you need to re-flash your smartphone using the smart_tool.exe, with the options DA DL Checksum checked.
To do so, follow these steps:
(1) Go to the Smart Phone Flash Tool (SP Flash Tool), click on the Options menu
(2) Click on the Download option, check "USB Checksum" and "EMMC Checksum". Close the window.
(3) On the Download tab, right below the "Download" button, select from the drop down box "Firmware Upgrade"
(4) Repeat the same procedure as your previous flashing. After a successful flash ROM, the smartphone should work again.