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authorDavid Woodhouse <dwmw2@infradead.org>2020-07-21 09:53:32 +0100
committerChuanhong Guo <gch981213@gmail.com>2020-07-26 16:42:35 +0800
commit6eb63019afef89404899f2cb65fb4c16e00aa0ed (patch)
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mediatek: mt7623: fix sysupgrade from vendor OpenWrt on UniElec U7623
This board ships with an ancient 14.07-based OpenWrt using block2mtd, and the MBR partition table contains nonsense. It is possible to sysupgrade to an upstream OpenWrt image, but the legacy layout of the OpenWrt images start at 0xA00 in the eMMC, with a raw uImage. The legacy OpenWrt image doesn't "own" the beginning of the device, including the MBR and U-Boot. This means that when a user upgrades to upstream OpenWrt, it doesn't boot because it can't find the right partitions. So hard-code them on the kernel's command line using CONFIG_CMDLINE_PARTITION (for block). Additionally, the vendor firmware doesn't cope with images larger than about 36MiB, because it only overwrites the contents of its "firmware" MTD partition. The current layout of the legacy image wastes a lot of space, allowing over 32MiB for the kernel and another 10MiB for the FAT recovery file system which is only created as 3MiB. So pull those in to allow 4¾ MiB for the kernel, 3MiB for recovery, and then we have over 20MiB for the root file system. This doesn't affect the new images which ship with a full eMMC image including a different MBR layout and a partition for U-Boot, because our modern U-Boot can actually pass the command line to the kernel, and the built-in one doesn't get used anyway. Tested by upgrading from vendor OpenWrt to the current legacy image, from legacy to itself, to the previous legacy layout, and then to finally the full-system image. This commit probably wants backporting to 19.07, which also doesn't install over the vendor OpenWrt and doesn't even have a full-system installation option. Signed-off-by: David Woodhouse <dwmw2@infradead.org>
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