Reduce spi-max-frequency for Xiaomi MI Router 4AG model
Xiaomi MI Router 4AG MTD uses two flash chips (no specific on router versions when produced from factory) - GD25Q128C and W25Q128BV.
These flash chips are capable of high frequency, but due to poor board design or manufacture process.
We are seeing the following errors in the linux kernel bootup:
`spi-nor spi0.0: unrecognized JEDEC id bytes: cc 60 1c cc 60 1c
spi-nor: probe of spi0.0 failed with error -2`
This causes the partitions not to be detected
`VFS: Cannot open root device "(null)" or unknown-block(0,0): error -6`
Then creates a bootloop and a bricked router.
The solution to limit this race condition is to reduce the frequency from 80 mhz to 50 mhz.
Signed-off-by: David Bentham <db260179@gmail.com>
(cherry picked from commit 17e690017d)
The Xiaomi Mi Router 4A Gigabit model has a race condition on bootup
causing the SQUASHFS data errors to appear and create a bootloop
scenario.
Adding the m25p,fast-read property resolves this issue.
Suggested-by: David Bentham <db260179@gmail.com>
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>
This device has previously been supported by the image
for Xiaomi Mi Router 3G v2. Since this is not obvious, the
4A is marketed as a new major revision and it also seems to
have a different bootloader, this will be both more tidy and
more helpful for the users.
Apart from that, note that there also is a 100M version of
the device that uses mt7628 platform, so a specifically named
image will also prevent confusion in this area.
Specifications:
- SoC: MediaTek MT7621
- Flash: 16 MiB NOR SPI
- RAM: 128 MiB DDR3
- Ethernet: 3x 10/100/1000 Mbps (switched, 2xLAN + WAN)
- WIFI0: MT7603E 2.4GHz 802.11b/g/n
- WIFI1: MT7612E 5GHz 802.11ac
- Antennas: 4x external (2 per radio), non-detachable
- LEDs: Programmable "power" LED (two-coloured, yellow/blue)
Non-programmable "internet" LED (shows WAN activity)
- Buttons: Reset
Installation:
Bootloader won't accept any serial input unless "boot_wait" u-boot
environment variable is changed to "on".
Vendor firmware won't accept any serial input until "uart_en" is
set to "1".
Using the https://github.com/acecilia/OpenWRTInvasion exploit you
can gain access to shell to enable these options:
To enable uart keyboard actions - 'nvram set uart_en=1'
To make uboot delay boot work - 'nvram set boot_wait=on'
Set boot delay to 5 - 'nvram set bootdelay=5'
Then run 'nvram commit' to make the changes permanent.
Once in the shell (following the OpenWRTInvasion instructions) you
can then run the following to flash OpenWrt and then reboot:
'cd /tmp; curl https://downloads.openwrt.org/...-sysupgrade.bin
--output firmware.bin; mtd -e OS1 -r write firmware.bin OS1'
Suggested-by: David Bentham <db260179@gmail.com>
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>
