linux: stm32mp1: dts: txmp: Remove st,use-ckin property from sdmmc3

[tronje]

With this property, the SD card reader does not work. SD cards are not detected, and additionally, periodic kernel panics occur:

INFO: task kworker/1:3:43 blocked for more than 122 seconds.
Not tainted 6.1.28-karo+gbf4ad6fa4e53 #1
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/1:3 state:D stack:0 pid:43 ppid:2 flags:0x00000000
Workqueue: events_freezable mmc_rescan
__schedule from schedule+0x5c/0xb8
schedule from schedule_timeout+0xc0/0xec
schedule_timeout from wait_for_completion+0x64/0x134
wait_for_completion from mmc_wait_for_req_done+0x7c/0xcc
mmc_wait_for_req_done from mmc_wait_for_cmd+0x6c/0xac
mmc_wait_for_cmd from sdio_reset+0x50/0x124
sdio_reset from mmc_rescan_try_freq+0x140/0x194
mmc_rescan_try_freq from mmc_rescan+0x16c/0x1e8
mmc_rescan from process_one_work+0x1b4/0x3c0
process_one_work from worker_thread+0x4c/0x4c8
worker_thread from kthread+0xe0/0xfc
kthread from ret_from_fork+0x14/0x2c
Exception stack(0xde8ddfb0 to 0xde8ddff8)
dfa0: 00000000 00000000 00000000 00000000
dfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
dfe0: 00000000 00000000 00000000 00000000 00000013 00000000
Kernel panic - not syncing: hung_task: blocked tasks

Not sure why that is exactly, but removing this property fixes it. Looking at mmci_probe_level_translator in drivers/mmc/host/mmci.c suggests that setting st,use-ckin without also setting the following properties doesn't make any sense:

• st,cmd-gpios
• st,ck-gpios
• st,ckin-gpios

See: https://github.com/torvalds/linux/blob/master/drivers/mmc/host/mmci.c#L2125-L2135

edit: I'm assuming this is actually the offending line: https://github.com/torvalds/linux/blob/master/drivers/mmc/host/mmci.c#L2123
See also the ST wiki: https://wiki.st.com/stm32mpu/wiki/SDMMC_device_tree_configuration

By setting this property, the sdmmc_ckin pin from an external transceiver is used to sample the receive data.

So this property should only be set if an external transceiver is connected, right?