mmc: sdhci-of-dwcmshc: Prevent illegal clock reduction in HS200/HS400 mode

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: mmc: sdhci-of-dwcmshc: Prevent illegal clock reduction in HS200/HS400 mode When operating in HS200 or HS400 timing modes, reducing the clock frequency below 52MHz will lead to link broken as the Rockchip DWC MSHC controller requires maintaining a minimum clock of 52MHz in these modes. Add a check to prevent illegal clock reduction through debugfs: root@debian:/# echo 50000000 > /sys/kernel/debug/mmc0/clock root@debian:/# [ 30.090146] mmc0: running CQE recovery mmc0: cqhci: Failed to halt mmc0: cqhci: spurious TCN for tag 0 WARNING: drivers/mmc/host/cqhci-core.c:797 at cqhci_irq+0x254/0x818, CPU#1: kworker/1:0H/24 Modules linked in: CPU: 1 UID: 0 PID: 24 Comm: kworker/1:0H Not tainted 6.19.0-rc1-00001-g09db0998649d-dirty #204 PREEMPT Hardware name: Rockchip RK3588 EVB1 V10 Board (DT) Workqueue: kblockd blk_mq_run_work_fn pstate: 604000c9 (nZCv daIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : cqhci_irq+0x254/0x818 lr : cqhci_irq+0x254/0x818 ...

References

• https://git.kernel.org/stable/c/59b8a1ca6df4db2ca250e9eeab74e2b0068d69e9
• https://git.kernel.org/stable/c/f2677d6e2bbc5ba2030825522d2afd0542b038a3
• https://git.kernel.org/stable/c/de0ad7156036a50982bcb75a080e4af284502be2
• https://git.kernel.org/stable/c/36be050f21dea7a3a76dff5a031da6274e8ee468
• https://git.kernel.org/stable/c/3009738a855cf938bbfc9078bec725031ae623a4