Hi Eishi SHIBUSAWA,
I have tested it on my board. The board and default BSP are boot up from EPDC. Here you want to boot up from QSPI, When using QSPI, you need tode-populate R388-R391, R396-R399 and populate R392-R395, R299, R300 in your hard ware.QSPI signals are muxed with EPDC_D[7:0].
In your above error message you can see that the system can not find and detect the qspi, so can not excute the following code,<CMD state="body="$ flash_erase /dev/mtd0 0 20">Erasing Boot partition</CMD>Updater" type="push" .

In a word, it's the hardware problem, you need do a little change. And it will work fine.
Have a great day,
Rita
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