I have replaced the 16M flash memory by 32M ( MacroniX MX25125635e ) because Samba4 is too big
modification
mt7620.mk
define Device/kimax_u25awf-h1
SOC := mt7620a
IMAGE_SIZE := 32448k
mt7620a_kimax_u25awf-h1.dts
partition@50000 {
compatible = "denx,uimage";
label = "firmware";
reg = <0x50000 0x1fb0000>;
build ...
no problem for flash with the new firmware ( overwrite , firstboot )
flash lasts long enough with the new flash ( old time * 2 !!! )