Unable to reboot

This is a bug. Any MT7621A device with 32M SPI cannot reboot normally. When you input reboot, you must plug out the power and plug in. Here is the solution (in Chinese)https://blog.csdn.net/yubing_615/article/details/52649489

解决方法 means solution.
转到drivers/mtd/devices/m25p80.c means change the code of drivers/mtd/devices/m25p80.c into the following code
Please fix this bug.

That article talks about Kernel 3.18, and was written in 2016. So it is at least a little bit out of date.
And as i recall, this issue was already fixed.