scsi: ufs: core: Hold a clock reference across the probe

Browse source

Clock gating becomes possible as soon as ufshcd_init_clk_gating() has run,
and from that point on the probe keeps accessing host registers without
ever taking a clock reference. This has been safe only because of the state
check in __ufshcd_release(): gate_work is not queued unless
hba->ufshcd_state is UFSHCD_STATE_OPERATIONAL, and the promotion to that
state used to happen after the last register access of the probe, at the
end of ufshcd_probe_hba().

That is fragile: it only works while the promotion happens after the
register accesses. Commit a390e6677f ("scsi: ufs: core: Expand the
ufshcd_device_init(hba, true) call") changed that ordering by moving the
promotion into ufshcd_init(), which schedules ufshcd_async_scan()
afterwards. ufshcd_probe_hba() therefore now runs with the state already
promoted, and it accesses host registers without holding a clock reference:

 - On hosts with UFSHCD_QUIRK_REINIT_AFTER_MAX_GEAR_SWITCH it calls
   ufshcd_hba_stop() and ufshcd_hba_enable() before ufshcd_device_init()
   sets the state back to UFSHCD_STATE_RESET, and both read
   REG_CONTROLLER_ENABLE, so gated clocks stall there instead of just
   losing a write.

 - It ends with an ufshcd_configure_auto_hibern8() write, which its other
   callers do take a clock reference for.

Take a clock reference as soon as clock gating has been initialised and
keep it until the probe is over. It then does not matter who drops a clock
reference while the probe is running, and the register accesses of the
probe no longer depend on hba->ufshcd_state. The reference is dropped by
ufshcd_async_scan() once the scan has finished, or by the new out_release
label if the probe fails after it was taken.

Fixes: a390e6677f ("scsi: ufs: core: Expand the ufshcd_device_init(hba, true) call")
Signed-off-by: Naomi Chu <naomi.chu@mediatek.com>
Reviewed-by: Peter Wang <peter.wang@mediatek.com>
Link: https://patch.msgid.link/20260909091045.1134956-1-naomi.chu@mediatek.com
Signed-off-by: Martin K. Petersen (Oracle) <mkp@kernel.org>

...

This commit is contained in:

Naomi Chu 2026-09-09 17:10:45 +08:00 • committed by Martin K. Petersen (Oracle)

parent 42d1221d32

commit 02a3178319

1 changed files with 14 additions and 8 deletions

Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL

Download patch file Download diff file Expand all files Collapse all files

22

drivers/ufs/core/ufshcd.c

View file