Re: [meta-rockchip][PATCH] use uuid instead of hard-coding root device

Trevor Woerner

On Fri 2021-09-17 @ 06:01:21 PM, Trevor Woerner via wrote:
Recent upstream kernel changes have made the mmc probing order unpredictable.
Therefore, boards with both an emmc and sdmmc interface aren't guaranteed to
boot with a hard-coded root device selected.

For example, on the rock64, with linux-yocto 5.10.y, using the uSD card (i.e.
the sdmmc interface) about 50% of the time the boot would succeed, and roughly
50% of the time it wouldn't:

[ 0.612233] Waiting for root device /dev/mmcblk1p7...
[ 0.634551] mmc_host mmc1: Bus speed (slot 0) = 300000Hz (slot req 300000Hz, actual 300000HZ div = 0)
[ 0.639064] mmc_host mmc0: Bus speed (slot 0) = 50000000Hz (slot req 50000000Hz, actual 50000000HZ di)
[ 0.640007] mmc0: new high speed SDXC card at address 5048
[ 0.641176] mmcblk0: mmc0:5048 SD64G 58.0 GiB
[ 0.647610] random: fast init done
[ 0.648279] GPT:Primary header thinks Alt. header is not at the end of the disk.
[ 0.648941] GPT:376479 != 121634815
[ 0.649252] GPT:Alternate GPT header not at the end of the disk.
[ 0.649796] GPT:376479 != 121634815
[ 0.650106] GPT: Use GNU Parted to correct GPT errors.
[ 0.650598] mmcblk0: p1 p2 p3 p4 p5 p6 p7

NOTE the discrepancy between the kernel waiting for device /dev/mmcblk1p7,
which comes from the hard-coded kernel cmdline, and the kernel probing putting
the sdmmc on mmcblk0.

With linux-yocto 5.13.y on the rock64 using the uSD card the board would never
boot, the sdmmc always appears on mmcblk0.

Instead of simply changing the hard-coded root device (i.e. from mmcblk0 to
mmcblk1) switch to using partition UUIDs instead. Hard-coding the boot device
would work with 5.13.y but would fail 50% of the time with 5.10.y; who knows
what other kernels will do?

In any case, switching to UUIDs works regardless of board, kernel, or
available mmc interfaces.

Boot tested on:
- rock64
- nanopi-m4-2gb
- tinker-board
- rock-pi-e
- rock-pi-4b

Signed-off-by: Trevor Woerner <twoerner@...>
conf/machine/include/ | 2 --
conf/machine/include/ | 2 --
conf/machine/include/ | 4 ----
conf/machine/rock64.conf | 3 ---
conf/machine/tinker-board-s.conf | 2 --
conf/machine/vyasa-rk3288.conf | 2 --
wic/rockchip.wks | 16 ++++++++--------
7 files changed, 8 insertions(+), 23 deletions(-)
Applied to meta-rockchip master.

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