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

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

[Manivannan Sadhasivam]

This reverts commit 85b2b966285498e1b551ac85f02c79cd06c0cff0.

Qcom UFS Host Controllers do not support scaling clocks when the traffic is
ongoing. But the offending commit removed the block I/O quiesce in the
clock scaling path, which causes below UFS failures during clock scaling:

ufshcd-qcom 1d84000.ufshc: ufshcd_check_errors: saved_err 0x80 saved_uic_err 0x0
ufshcd-qcom 1d84000.ufshc: ufshcd_err_handler started; HBA state eh_fatal; powered 1; shutting down 0; saved_err = 0x80; saved_uic_err = 0x0; force_reset = 0
ufshcd-qcom 1d84000.ufshc: pwr ctrl cmd 0x2 with (MIBattribute 0x1571, mode 0x11) completion timeout
ufshcd-qcom 1d84000.ufshc: UFS Host state=3
ufshcd-qcom 1d84000.ufshc: 7 outstanding reqs, tasks=0x0
ufshcd-qcom 1d84000.ufshc: saved_err=0x80, saved_uic_err=0x0
ufshcd-qcom 1d84000.ufshc: Device power mode=1, UIC link state=1
ufshcd-qcom 1d84000.ufshc: PM in progress=0, sys. suspended=0
ufshcd-qcom 1d84000.ufshc: Auto BKOPS=0, Host self-block=0
ufshcd-qcom 1d84000.ufshc: Clk gate=1
ufshcd-qcom 1d84000.ufshc: last_hibern8_exit_tstamp at 196451913 us, hibern8_exit_cnt=20
ufshcd-qcom 1d84000.ufshc: error handling flags=0x0, req. abort count=0
ufshcd-qcom 1d84000.ufshc: hba->ufs_version=0x300, Host capabilities=0x1587031f, caps=0x124f
ufshcd-qcom 1d84000.ufshc: quirks=0x0, dev. quirks=0x310c4
ufshcd-qcom 1d84000.ufshc: UFS dev info: SAMSUNG  KLUDG4UHDB-B2D1  rev 0400
ufshcd-qcom 1d84000.ufshc: clk: core_clk, rate: 300000000
ufshcd-qcom 1d84000.ufshc: clk: core_clk_unipro, rate: 300000000

Hence, revert the commit to bring back UFS on all Qcom platforms.

Reported-by: Shawn Guo <shengchao.guo@oss.qualcomm.com>
Closes: https://lore.kernel.org/linux-scsi/al8YkXydXJQZrl_Y@QCOM-aGQu4IUr3Y
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@oss.qualcomm.com>
---
 drivers/ufs/core/ufshcd.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
index 79331c2bd38d..1a5a851d43b2 100644
--- a/drivers/ufs/core/ufshcd.c
+++ b/drivers/ufs/core/ufshcd.c
@@ -1445,7 +1445,7 @@ static int ufshcd_scale_gear(struct ufs_hba *hba, u32 target_gear, bool scale_up
  *
  * Return: 0 upon success; -EBUSY upon timeout.
  */
-static int ufshcd_clock_scaling_prepare(struct ufs_hba *hba)
+static int ufshcd_clock_scaling_prepare(struct ufs_hba *hba, u64 timeout_us)
 {
 	int ret = 0;
 	/*
@@ -1453,13 +1453,16 @@ static int ufshcd_clock_scaling_prepare(struct ufs_hba *hba)
 	 * clock scaling is in progress
 	 */
 	mutex_lock(&hba->host->scan_mutex);
+	blk_mq_quiesce_tagset(&hba->host->tag_set);
 	mutex_lock(&hba->wb_mutex);
 	down_write(&hba->clk_scaling_lock);
 
-	if (!hba->clk_scaling.is_allowed) {
+	if (!hba->clk_scaling.is_allowed ||
+	    ufshcd_wait_for_pending_cmds(hba, timeout_us)) {
 		ret = -EBUSY;
 		up_write(&hba->clk_scaling_lock);
 		mutex_unlock(&hba->wb_mutex);
+		blk_mq_unquiesce_tagset(&hba->host->tag_set);
 		mutex_unlock(&hba->host->scan_mutex);
 		goto out;
 	}
@@ -1475,6 +1478,7 @@ static void ufshcd_clock_scaling_unprepare(struct ufs_hba *hba, int err)
 {
 	up_write(&hba->clk_scaling_lock);
 	mutex_unlock(&hba->wb_mutex);
+	blk_mq_unquiesce_tagset(&hba->host->tag_set);
 	mutex_unlock(&hba->host->scan_mutex);
 
 	/* Enable Write Booster if current gear requires it else disable it */
@@ -1502,7 +1506,7 @@ static int ufshcd_devfreq_scale(struct ufs_hba *hba, unsigned long freq,
 
 	new_gear = ufshcd_vops_freq_to_gear_speed(hba, freq);
 
-	ret = ufshcd_clock_scaling_prepare(hba);
+	ret = ufshcd_clock_scaling_prepare(hba, 1 * USEC_PER_SEC);
 	if (ret)
 		return ret;
 
-- 
2.43.0

Re: [PATCH] Revert "scsi: ufs: core: Remove unnecessary block I/O quiesce for clock scaling"

[Konrad Dybcio]

On 7/23/26 2:47 PM, Manivannan Sadhasivam wrote:
> This reverts commit 85b2b966285498e1b551ac85f02c79cd06c0cff0.
> 
> Qcom UFS Host Controllers do not support scaling clocks when the traffic is
> ongoing. But the offending commit removed the block I/O quiesce in the
> clock scaling path, which causes below UFS failures during clock scaling:
> 
> ufshcd-qcom 1d84000.ufshc: ufshcd_check_errors: saved_err 0x80 saved_uic_err 0x0
> ufshcd-qcom 1d84000.ufshc: ufshcd_err_handler started; HBA state eh_fatal; powered 1; shutting down 0; saved_err = 0x80; saved_uic_err = 0x0; force_reset = 0
> ufshcd-qcom 1d84000.ufshc: pwr ctrl cmd 0x2 with (MIBattribute 0x1571, mode 0x11) completion timeout
> ufshcd-qcom 1d84000.ufshc: UFS Host state=3
> ufshcd-qcom 1d84000.ufshc: 7 outstanding reqs, tasks=0x0
> ufshcd-qcom 1d84000.ufshc: saved_err=0x80, saved_uic_err=0x0
> ufshcd-qcom 1d84000.ufshc: Device power mode=1, UIC link state=1
> ufshcd-qcom 1d84000.ufshc: PM in progress=0, sys. suspended=0
> ufshcd-qcom 1d84000.ufshc: Auto BKOPS=0, Host self-block=0
> ufshcd-qcom 1d84000.ufshc: Clk gate=1
> ufshcd-qcom 1d84000.ufshc: last_hibern8_exit_tstamp at 196451913 us, hibern8_exit_cnt=20
> ufshcd-qcom 1d84000.ufshc: error handling flags=0x0, req. abort count=0
> ufshcd-qcom 1d84000.ufshc: hba->ufs_version=0x300, Host capabilities=0x1587031f, caps=0x124f
> ufshcd-qcom 1d84000.ufshc: quirks=0x0, dev. quirks=0x310c4
> ufshcd-qcom 1d84000.ufshc: UFS dev info: SAMSUNG  KLUDG4UHDB-B2D1  rev 0400
> ufshcd-qcom 1d84000.ufshc: clk: core_clk, rate: 300000000
> ufshcd-qcom 1d84000.ufshc: clk: core_clk_unipro, rate: 300000000
> 
> Hence, revert the commit to bring back UFS on all Qcom platforms.
> 
> Reported-by: Shawn Guo <shengchao.guo@oss.qualcomm.com>
> Closes: https://lore.kernel.org/linux-scsi/al8YkXydXJQZrl_Y@QCOM-aGQu4IUr3Y
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@oss.qualcomm.com>
> ---

Tested-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com> # SC8280XP CRD

Konrad

Re: [PATCH] Revert "scsi: ufs: core: Remove unnecessary block I/O quiesce for clock scaling"

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] Calling blk_mq_quiesce_tagset() before acquiring the clk_scaling_lock write semaphore introduces an ABBA deadlock with device management commands.
--

--- Patch [1]: [PATCH] Revert "scsi: ufs: core: Remove unnecessary block I/O quiesce for clock scaling" ---
commit d454cd4e623d4ff192ea3b557d6b1e8c27de2a9a
Author: Manivannan Sadhasivam <manivannan.sadhasivam@oss.qualcomm.com>

Revert "scsi: ufs: core: Remove unnecessary block I/O quiesce for clock scaling"

This commit reverts a previous change to restore the block I/O quiesce
during clock scaling preparation. It is intended to fix UFS failures
during clock scaling on Qcom platforms.

Closes: https://lore.kernel.org/linux-scsi/al8YkXydXJQZrl_Y@QCOM-aGQu4IUr3Y

> diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
> index 79331c2bd38de..1a5a851d43b28 100644
> --- a/drivers/ufs/core/ufshcd.c
> +++ b/drivers/ufs/core/ufshcd.c

[ ... ]

> @@ -1445,7 +1445,7 @@ static int ufshcd_scale_gear(struct ufs_hba *hba, u32 target_gear, bool scale_up
>   *
>   * Return: 0 upon success; -EBUSY upon timeout.
>   */
> -static int ufshcd_clock_scaling_prepare(struct ufs_hba *hba)
> +static int ufshcd_clock_scaling_prepare(struct ufs_hba *hba, u64 timeout_us)
>  {
>  	int ret = 0;
>  	/*
> @@ -1453,13 +1453,16 @@ static int ufshcd_clock_scaling_prepare(struct ufs_hba *hba)
>  	 * clock scaling is in progress
>  	 */
>  	mutex_lock(&hba->host->scan_mutex);
> +	blk_mq_quiesce_tagset(&hba->host->tag_set);
>  	mutex_lock(&hba->wb_mutex);
>  	down_write(&hba->clk_scaling_lock);

[Severity: High]
Could this sequencing introduce a deadlock between clock scaling and
device management commands?

If a device management command starts first, it acquires the read lock in
ufshcd_dev_man_lock():

ufshcd_dev_man_lock()
    down_read(&hba->clk_scaling_lock);

If the devfreq scaling worker then calls ufshcd_clock_scaling_prepare(),
it will quiesce the block queue and block waiting for the write lock:

ufshcd_clock_scaling_prepare()
    blk_mq_quiesce_tagset(&hba->host->tag_set);
    down_write(&hba->clk_scaling_lock);

When the device management thread proceeds to execute its request via
ufshcd_issue_dev_cmd() calling blk_execute_rq(), the request gets queued but
will not dispatch because the queue is quiesced. 

Since blk_execute_rq() blocks indefinitely and the block layer timeout
doesn't track requests that haven't dispatched yet, won't this result in
both threads hanging permanently?

> -	if (!hba->clk_scaling.is_allowed) {
> +	if (!hba->clk_scaling.is_allowed ||
> +	    ufshcd_wait_for_pending_cmds(hba, timeout_us)) {
>  		ret = -EBUSY;
>  		up_write(&hba->clk_scaling_lock);
>  		mutex_unlock(&hba->wb_mutex);
> +		blk_mq_unquiesce_tagset(&hba->host->tag_set);
>  		mutex_unlock(&hba->host->scan_mutex);
>  		goto out;
>  	}

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260723124733.341789-1-manivannan.sadhasivam@oss.qualcomm.com?part=1

Re: [PATCH] Revert "scsi: ufs: core: Remove unnecessary block I/O quiesce for clock scaling"

[Peter Wang (王信友)]

On Thu, 2026-07-23 at 14:47 +0200, Manivannan Sadhasivam wrote:
> This reverts commit 85b2b966285498e1b551ac85f02c79cd06c0cff0.
> 
> Qcom UFS Host Controllers do not support scaling clocks when the
> traffic is
> ongoing. But the offending commit removed the block I/O quiesce in
> the
> clock scaling path, which causes below UFS failures during clock
> scaling:
> 
> ufshcd-qcom 1d84000.ufshc: ufshcd_check_errors: saved_err 0x80
> saved_uic_err 0x0
> ufshcd-qcom 1d84000.ufshc: ufshcd_err_handler started; HBA state
> eh_fatal; powered 1; shutting down 0; saved_err = 0x80; saved_uic_err
> = 0x0; force_reset = 0
> ufshcd-qcom 1d84000.ufshc: pwr ctrl cmd 0x2 with (MIBattribute
> 0x1571, mode 0x11) completion timeout
> ufshcd-qcom 1d84000.ufshc: UFS Host state=3
> ufshcd-qcom 1d84000.ufshc: 7 outstanding reqs, tasks=0x0
> ufshcd-qcom 1d84000.ufshc: saved_err=0x80, saved_uic_err=0x0
> ufshcd-qcom 1d84000.ufshc: Device power mode=1, UIC link state=1
> ufshcd-qcom 1d84000.ufshc: PM in progress=0, sys. suspended=0
> ufshcd-qcom 1d84000.ufshc: Auto BKOPS=0, Host self-block=0
> ufshcd-qcom 1d84000.ufshc: Clk gate=1
> ufshcd-qcom 1d84000.ufshc: last_hibern8_exit_tstamp at 196451913 us,
> hibern8_exit_cnt=20
> ufshcd-qcom 1d84000.ufshc: error handling flags=0x0, req. abort
> count=0
> ufshcd-qcom 1d84000.ufshc: hba->ufs_version=0x300, Host
> capabilities=0x1587031f, caps=0x124f
> ufshcd-qcom 1d84000.ufshc: quirks=0x0, dev. quirks=0x310c4
> ufshcd-qcom 1d84000.ufshc: UFS dev info: SAMSUNG  KLUDG4UHDB-B2D1 
> rev 0400
> ufshcd-qcom 1d84000.ufshc: clk: core_clk, rate: 300000000
> ufshcd-qcom 1d84000.ufshc: clk: core_clk_unipro, rate: 300000000
> 
> Hence, revert the commit to bring back UFS on all Qcom platforms.
> 
> Reported-by: Shawn Guo <shengchao.guo@oss.qualcomm.com>
> Closes:
> https://lore.kernel.org/linux-scsi/al8YkXydXJQZrl_Y@QCOM-aGQu4IUr3Y
> Signed-off-by: Manivannan Sadhasivam
> <manivannan.sadhasivam@oss.qualcomm.com>
> ---

Reviewed-by: Peter Wang <peter.wang@mediatek.com>

Re: [PATCH] Revert "scsi: ufs: core: Remove unnecessary block I/O quiesce for clock scaling"

[Bart Van Assche]

On 7/23/26 5:47 AM, Manivannan Sadhasivam wrote:
> This reverts commit 85b2b966285498e1b551ac85f02c79cd06c0cff0.
Reviewed-by: Bart Van Assche <bvanassche@acm.org>

Re: [PATCH] Revert "scsi: ufs: core: Remove unnecessary block I/O quiesce for clock scaling"

[Shawn Guo]

On Thu, Jul 23, 2026 at 02:47:33PM +0200, Manivannan Sadhasivam wrote:
> This reverts commit 85b2b966285498e1b551ac85f02c79cd06c0cff0.
> 
> Qcom UFS Host Controllers do not support scaling clocks when the traffic is
> ongoing. But the offending commit removed the block I/O quiesce in the
> clock scaling path, which causes below UFS failures during clock scaling:
> 
> ufshcd-qcom 1d84000.ufshc: ufshcd_check_errors: saved_err 0x80 saved_uic_err 0x0
> ufshcd-qcom 1d84000.ufshc: ufshcd_err_handler started; HBA state eh_fatal; powered 1; shutting down 0; saved_err = 0x80; saved_uic_err = 0x0; force_reset = 0
> ufshcd-qcom 1d84000.ufshc: pwr ctrl cmd 0x2 with (MIBattribute 0x1571, mode 0x11) completion timeout
> ufshcd-qcom 1d84000.ufshc: UFS Host state=3
> ufshcd-qcom 1d84000.ufshc: 7 outstanding reqs, tasks=0x0
> ufshcd-qcom 1d84000.ufshc: saved_err=0x80, saved_uic_err=0x0
> ufshcd-qcom 1d84000.ufshc: Device power mode=1, UIC link state=1
> ufshcd-qcom 1d84000.ufshc: PM in progress=0, sys. suspended=0
> ufshcd-qcom 1d84000.ufshc: Auto BKOPS=0, Host self-block=0
> ufshcd-qcom 1d84000.ufshc: Clk gate=1
> ufshcd-qcom 1d84000.ufshc: last_hibern8_exit_tstamp at 196451913 us, hibern8_exit_cnt=20
> ufshcd-qcom 1d84000.ufshc: error handling flags=0x0, req. abort count=0
> ufshcd-qcom 1d84000.ufshc: hba->ufs_version=0x300, Host capabilities=0x1587031f, caps=0x124f
> ufshcd-qcom 1d84000.ufshc: quirks=0x0, dev. quirks=0x310c4
> ufshcd-qcom 1d84000.ufshc: UFS dev info: SAMSUNG  KLUDG4UHDB-B2D1  rev 0400
> ufshcd-qcom 1d84000.ufshc: clk: core_clk, rate: 300000000
> ufshcd-qcom 1d84000.ufshc: clk: core_clk_unipro, rate: 300000000
> 
> Hence, revert the commit to bring back UFS on all Qcom platforms.
> 
> Reported-by: Shawn Guo <shengchao.guo@oss.qualcomm.com>
> Closes: https://lore.kernel.org/linux-scsi/al8YkXydXJQZrl_Y@QCOM-aGQu4IUr3Y
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@oss.qualcomm.com>

Tested-by: Shawn Guo <shengchao.guo@oss.qualcomm.com> # Qualcomm Nord SoC