[PATCH v1] ufs: core: Remove unnecessary block I/O quiesce for clock scaling

[Shawn Guo]

On Thu, Jun 04, 2026 at 09:33:58PM +0800, peter.wang at mediatek.com wrote:
> From: Peter Wang <peter.wang at mediatek.com>
> 
> According to the MIPI UniPro Specification v2.0:
> 
> 5.3.2.3 PA_DL_PAUSE.ind
> This primitive informs the PA Service User, the DL Layer in
> this case, that the PA Layer was requested to execute a
> operation that requires the usage of the Link, e.g. Power
> Mode change or PACP frame transmission.
> 
> 5.3.2.4 PA_DL_PAUSE.rsp_L
> This primitive informs the Service Provider that the PA
> Service User, the DL Layer in this case, has reached
> a state where the Link may be used by the PA Layer.
> 
> 5.3.2.5 PA_DL_RESUME.ind
> This primitive informs the PA Service User, the DL Layer
> in this case, that the PA Layer has completed its operation
> and the DL Layer may continue to use the Link.
> 
> The detailed flow can be found in Figure 52:
> Power Mode Change Using PACP_PWR_req and PACP_PWR_cnf.
> 
> In short, when the PA layer do power mode change:
> 1. The DL layer receives PA_DL_PAUSE.ind.
> 2. The DL layer stops and responds to the PA layer with PA_DL_PAUSE.rsp_L.
> 3. Waits until the PA layer has completed its work.
> 4. The PA layer then informs the DL layer with PA_DL_RESUME.ind.
> 
> Hence, it is not necessary to stop I/O during a power mode change,
> and this step can be removed.
> 
> Signed-off-by: Peter Wang <peter.wang at mediatek.com>

I'm testing linux-next on a Qualcomm platform. UFS worked fine on
next-20260713 and got a regression on next-20260720 like:

[   36.243001] ufshcd-qcom 1d44000.ufshc: ufshcd_abort: Device abort task at tag 48
[   36.250616] sd 0:0:0:5: [sdf] tag#48 CDB: opcode=0x28 28 00 00 02 5f 32 00 00 10 00
[   36.258521] host_regs: 00000000: d5c7033f 20e0071f 00000400 00000000
[   36.265065] host_regs: 00000010: 01000000 00010217 00000c96 00000000
[   36.271607] host_regs: 00000020: 00000000 00371af5 00000000 00000000
[   36.278146] host_regs: 00000030: 0000010f 00000003 00000000 00000000
[   36.284688] host_regs: 00000040: 00000000 00000000 00000000 00000000
[   36.291229] host_regs: 00000050: fffdf000 0000000f 00000000 00000000
[   36.297775] host_regs: 00000060: 00000001 00000000 00000000 00000000
[   36.304317] host_regs: 00000070: fffde000 0000000f 00000000 00000000
[   36.310860] host_regs: 00000080: 00000001 00000000 00000000 00000000
[   36.317403] host_regs: 00000090: 00000002 15710000 00000000 00000004
[   36.323939] ufshcd-qcom 1d44000.ufshc: No record of pa_err
[   36.329595] ufshcd-qcom 1d44000.ufshc: No record of dl_err
[   36.335237] ufshcd-qcom 1d44000.ufshc: No record of nl_err
[   36.340878] ufshcd-qcom 1d44000.ufshc: No record of tl_err
[   36.346523] ufshcd-qcom 1d44000.ufshc: No record of dme_err
[   36.352252] ufshcd-qcom 1d44000.ufshc: No record of auto_hibern8_err
[   36.358790] ufshcd-qcom 1d44000.ufshc: No record of fatal_err
[   36.364701] ufshcd-qcom 1d44000.ufshc: No record of link_startup_fail
[   36.371332] ufshcd-qcom 1d44000.ufshc: No record of resume_fail
[   36.377428] ufshcd-qcom 1d44000.ufshc: No record of suspend_fail
[   36.383603] ufshcd-qcom 1d44000.ufshc: No record of wlun resume_fail
[   36.390142] ufshcd-qcom 1d44000.ufshc: No record of wlun suspend_fail
[   36.396769] ufshcd-qcom 1d44000.ufshc: dev_reset[0] = 0x0 at 3853838 us
[   36.403575] ufshcd-qcom 1d44000.ufshc: dev_reset: total cnt=1
[   36.409482] ufshcd-qcom 1d44000.ufshc: No record of host_reset
[   36.415478] ufshcd-qcom 1d44000.ufshc: task_abort[0] = 0x30 at 36258488 us
[   36.422546] ufshcd-qcom 1d44000.ufshc: task_abort: total cnt=1
[   36.428550] ufshcd-qcom 1d44000.ufshc: HW_H8_ENTER_CNT=2
[   36.434015] ufshcd-qcom 1d44000.ufshc: HW_H8_EXIT_CNT=1
[   36.439393] ufshcd-qcom 1d44000.ufshc: SW_H8_ENTER_CNT=3
[   36.444861] ufshcd-qcom 1d44000.ufshc: SW_H8_EXIT_CNT=4
[   36.450239] ufshcd-qcom 1d44000.ufshc: SW_AFTER_HW_H8_ENTER_CNT=1
[   36.456526] HCI Vendor Specific Registers 00000000: 00000193 00000000 00000000 00000000
[   36.464758] HCI Vendor Specific Registers 00000010: 002aaa52 00000000 00000001 1c00052c
[   36.472987] HCI Vendor Specific Registers 00000020: 1b0113ff 60020000 00000000 00000000
[   36.481216] HCI Vendor Specific Registers 00000030: 00000000 00000000 00000000 0000183c
[   36.489481] UFS_UFS_DBG_RD_REG_OCSC 00000000: 00000000 00000000 00000000 00000000
[   36.497175] UFS_UFS_DBG_RD_REG_OCSC 00000010: 00000000 00000000 00000000 00000000
[   36.504867] UFS_UFS_DBG_RD_REG_OCSC 00000020: 00000000 00000000 00000000 00000000
[   36.512558] UFS_UFS_DBG_RD_REG_OCSC 00000030: 00000000 00000013 00000000 00000000
...

A revert of commit 85b2b9662854 ("scsi: ufs: core: Remove unnecessary
block I/O quiesce for clock scaling") fixes the regression for me.

Shawn