[PATCH 4/4] scsi: ufs: Add suspend/resume SCSI command processing support

[Bart Van Assche <bvanassche@acm.org>]

This functionality is needed by UFS drivers to e.g. suspend SCSI command
processing while reprogramming encryption keys if the hardware does not
support concurrent I/O and key reprogramming.

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 drivers/scsi/ufs/ufshcd.c | 20 ++++++++++++++++++++
 drivers/scsi/ufs/ufshcd.h |  3 +++
 2 files changed, 23 insertions(+)

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index 60ba11b68735..22447c4f16a2 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -1692,6 +1692,26 @@ static void ufshcd_ungate_work(struct work_struct *work)
 	ufshcd_scsi_unblock_requests(hba);
 }
 
+/*
+ * Block processing of new SCSI commands and wait until pending SCSI
+ * commands and TMFs have finished. ufshcd_exec_dev_cmd() and
+ * ufshcd_issue_devman_upiu_cmd() are not affected by this function.
+ *
+ * Return: 0 upon success; -EBUSY upon timeout.
+ */
+int ufshcd_freeze_scsi_devs(struct ufs_hba *hba, u64 timeout_us)
+{
+	return ufshcd_clock_scaling_prepare(hba, timeout_us);
+}
+EXPORT_SYMBOL_GPL(ufshcd_freeze_scsi_devs);
+
+/* Resume processing of SCSI commands. */
+void ufshcd_unfreeze_scsi_devs(struct ufs_hba *hba)
+{
+	ufshcd_clock_scaling_unprepare(hba, true);
+}
+EXPORT_SYMBOL_GPL(ufshcd_unfreeze_scsi_devs);
+
 /**
  * ufshcd_hold - Enable clocks that were gated earlier due to ufshcd_release.
  * Also, exit from hibern8 mode and set the link as active.
diff --git a/drivers/scsi/ufs/ufshcd.h b/drivers/scsi/ufs/ufshcd.h
index 2b0f3441b813..8954fcbdaf6f 100644
--- a/drivers/scsi/ufs/ufshcd.h
+++ b/drivers/scsi/ufs/ufshcd.h
@@ -1181,6 +1181,9 @@ void ufshcd_release(struct ufs_hba *hba);
 
 void ufshcd_clkgate_delay_set(struct device *dev, unsigned long value);
 
+int ufshcd_freeze_scsi_devs(struct ufs_hba *hba, u64 timeout_us);
+void ufshcd_unfreeze_scsi_devs(struct ufs_hba *hba);
+
 void ufshcd_map_desc_id_to_length(struct ufs_hba *hba, enum desc_idn desc_id,
 				  int *desc_length);