[PATCH v3 06/12] scsi: ufs: core: Add helpers to pause and resume command processing

[Can Guo <can.guo@oss.qualcomm.com>]

In preparation for supporting TX Equalization refreshing, introduce
helper functions to safely pause and resume command processing.

ufshcd_pause_command_processing() ensures the host is in a quiescent
state by stopping the block layer tagset, acquiring the necessary
locks (scan_mutex and clk_scaling_lock), and waiting for any
in-flight commands to complete within a specified timeout.

ufshcd_resume_command_processing() restores the host to its previous
operational state by reversing these steps in the correct order.

Signed-off-by: Can Guo <can.guo@oss.qualcomm.com>
---
 drivers/ufs/core/ufshcd-priv.h |  2 ++
 drivers/ufs/core/ufshcd.c      | 42 ++++++++++++++++++++++++++++++++++
 2 files changed, 44 insertions(+)

diff --git a/drivers/ufs/core/ufshcd-priv.h b/drivers/ufs/core/ufshcd-priv.h
index 20ec8d8ac0a4..2303d57bf874 100644
--- a/drivers/ufs/core/ufshcd-priv.h
+++ b/drivers/ufs/core/ufshcd-priv.h
@@ -78,6 +78,8 @@ int ufshcd_mcq_sq_cleanup(struct ufs_hba *hba, int task_tag);
 int ufshcd_mcq_abort(struct scsi_cmnd *cmd);
 int ufshcd_try_to_abort_task(struct ufs_hba *hba, int tag);
 void ufshcd_release_scsi_cmd(struct ufs_hba *hba, struct scsi_cmnd *cmd);
+int ufshcd_pause_command_processing(struct ufs_hba *hba, u64 timeout_us);
+void ufshcd_resume_command_processing(struct ufs_hba *hba);
 
 /**
  * enum ufs_descr_fmt - UFS string descriptor format
diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
index 15543ad03181..6fef24612be1 100644
--- a/drivers/ufs/core/ufshcd.c
+++ b/drivers/ufs/core/ufshcd.c
@@ -1362,6 +1362,48 @@ static int ufshcd_wait_for_pending_cmds(struct ufs_hba *hba,
 	return ret;
 }
 
+/**
+ * ufshcd_pause_command_processing - Pause command processing
+ * @hba: per-adapter instance
+ * @timeout_us: timeout in microseconds to wait for pending commands to finish
+ *
+ * This function stops new command submissions and waits for existing commands
+ * to complete.
+ *
+ * Return: 0 on success, %-EBUSY if commands did not finish within @timeout_us.
+ * On failure, all acquired locks are released and the tagset is unquiesced.
+ */
+int ufshcd_pause_command_processing(struct ufs_hba *hba, u64 timeout_us)
+{
+	int ret = 0;
+
+	mutex_lock(&hba->host->scan_mutex);
+	blk_mq_quiesce_tagset(&hba->host->tag_set);
+	down_write(&hba->clk_scaling_lock);
+
+	if (ufshcd_wait_for_pending_cmds(hba, timeout_us)) {
+		ret = -EBUSY;
+		up_write(&hba->clk_scaling_lock);
+		blk_mq_unquiesce_tagset(&hba->host->tag_set);
+		mutex_unlock(&hba->host->scan_mutex);
+	}
+
+	return ret;
+}
+
+/**
+ * ufshcd_resume_command_processing - Resume command processing
+ * @hba: per-adapter instance
+ *
+ * This function resumes command submissions.
+ */
+void ufshcd_resume_command_processing(struct ufs_hba *hba)
+{
+	up_write(&hba->clk_scaling_lock);
+	blk_mq_unquiesce_tagset(&hba->host->tag_set);
+	mutex_unlock(&hba->host->scan_mutex);
+}
+
 /**
  * ufshcd_scale_gear - scale up/down UFS gear
  * @hba: per adapter instance
-- 
2.34.1