[PATCH v10 0/3] Three changes related with UFS clock scaling

[PATCH v10 0/3] Three changes related with UFS clock scaling

[Can Guo]

This series is made based on 5.12/scsi-queue branch.

Current devfreq framework allows sysfs nodes like governor, min_freq and max_freq to be changed even after devfreq device is suspended.
Meanwhile, devfreq_suspend_device() cannot/wouldn't synchronize clock scaling which has already been invoked through devfreq sysfs nodes menitioned above.
It means that clock scaling invoked through these devfreq sysfs nodes can happen at any time regardless of the state of UFS host and/or device.
We need to control and synchronize clock scaling in this scenario.

The 1st change allows contexts to prevent clock scaling from being invoked through devfreq sysfs nodes.
The 2nd change is just a code cleanup for clk_scaling/gating initialization routine.
The 3rd change reverts one old change which can be covered by the 1st change. For branches which do not have this change yet, it can be ignored.

Change since v9:
- Minor update in the 1st change.

Change since v8:
- Rebased on 5.12/scsi-queue

Change since v7:
- Slightly updated the 1st change: changed the up_write() before ufshcd_wb_ctrl() to downgrade_write() in ufshcd_devfreq_scale(),
  so that ufshcd_wb_ctrl() is called with clk_scale_lock held, this is to make sure race condition won't happen to ufshcd_wb_ctrl().

Change since v6:
- Updated the 2nd change

Change since v5:
- Reomved the code change in ufshcd_shutdown() since it is not quite relevant with this fix

Change since v4:
- Updated some comment lines as requested by Stanley

Change since v3:
- Slightly updated the 1st change

Change since v2:
- Split the 1st change to two changes, which become the 1st change and the 3rd change

Change since v1:
- Updated the 2nd change

*** BLURB HERE ***

Can Guo (3):
  scsi: ufs: Protect some contexts from unexpected clock scaling
  scsi: ufs: Refactor ufshcd_init/exit_clk_scaling/gating()
  scsi: ufs: Revert "Make sure clk scaling happens only when HBA is
    runtime ACTIVE"

 drivers/scsi/ufs/ufshcd.c | 214 +++++++++++++++++++++++++---------------------
 drivers/scsi/ufs/ufshcd.h |  10 ++-
 2 files changed, 127 insertions(+), 97 deletions(-)

-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project.

[PATCH v10 1/3] scsi: ufs: Protect some contexts from unexpected clock scaling

[Can Guo]

In contexts like suspend, shutdown and error handling, we need to suspend
devfreq to make sure these contexts won't be disturbed by clock scaling.
However, suspending devfreq is not enough since users can still trigger a
clock scaling by manipulating the devfreq sysfs nodes like min/max_freq and
governor even after devfreq is suspended. Moreover, mere suspending devfreq
cannot synchroinze a clock scaling which has already been invoked through
these sysfs nodes. Add one more flag in struct clk_scaling and wrap the
entire func ufshcd_devfreq_scale() with the clk_scaling_lock, so that we
can use this flag and clk_scaling_lock to control and synchronize clock
scaling invoked through devfreq sysfs nodes.

Signed-off-by: Can Guo <cang@codeaurora.org>
---
 drivers/scsi/ufs/ufshcd.c | 83 +++++++++++++++++++++++++++++------------------
 drivers/scsi/ufs/ufshcd.h |  6 +++-
 2 files changed, 56 insertions(+), 33 deletions(-)

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index 53fd59c..ba62d84 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -1201,19 +1201,30 @@ static int ufshcd_clock_scaling_prepare(struct ufs_hba *hba)
 	 */
 	ufshcd_scsi_block_requests(hba);
 	down_write(&hba->clk_scaling_lock);
-	if (ufshcd_wait_for_doorbell_clr(hba, DOORBELL_CLR_TOUT_US)) {
+
+	if (!hba->clk_scaling.is_allowed ||
+	    ufshcd_wait_for_doorbell_clr(hba, DOORBELL_CLR_TOUT_US)) {
 		ret = -EBUSY;
 		up_write(&hba->clk_scaling_lock);
 		ufshcd_scsi_unblock_requests(hba);
+		goto out;
 	}
 
+	/* let's not get into low power until clock scaling is completed */
+	ufshcd_hold(hba, false);
+
+out:
 	return ret;
 }
 
-static void ufshcd_clock_scaling_unprepare(struct ufs_hba *hba)
+static void ufshcd_clock_scaling_unprepare(struct ufs_hba *hba, bool writelock)
 {
-	up_write(&hba->clk_scaling_lock);
+	if (writelock)
+		up_write(&hba->clk_scaling_lock);
+	else
+		up_read(&hba->clk_scaling_lock);
 	ufshcd_scsi_unblock_requests(hba);
+	ufshcd_release(hba);
 }
 
 /**
@@ -1228,13 +1239,11 @@ static void ufshcd_clock_scaling_unprepare(struct ufs_hba *hba)
 static int ufshcd_devfreq_scale(struct ufs_hba *hba, bool scale_up)
 {
 	int ret = 0;
-
-	/* let's not get into low power until clock scaling is completed */
-	ufshcd_hold(hba, false);
+	bool is_writelock = true;
 
 	ret = ufshcd_clock_scaling_prepare(hba);
 	if (ret)
-		goto out;
+		return ret;
 
 	/* scale down the gear before scaling down clocks */
 	if (!scale_up) {
@@ -1260,14 +1269,12 @@ static int ufshcd_devfreq_scale(struct ufs_hba *hba, bool scale_up)
 	}
 
 	/* Enable Write Booster if we have scaled up else disable it */
-	up_write(&hba->clk_scaling_lock);
+	downgrade_write(&hba->clk_scaling_lock);
+	is_writelock = false;
 	ufshcd_wb_ctrl(hba, scale_up);
-	down_write(&hba->clk_scaling_lock);
 
 out_unprepare:
-	ufshcd_clock_scaling_unprepare(hba);
-out:
-	ufshcd_release(hba);
+	ufshcd_clock_scaling_unprepare(hba, is_writelock);
 	return ret;
 }
 
@@ -1541,7 +1548,7 @@ static ssize_t ufshcd_clkscale_enable_show(struct device *dev,
 {
 	struct ufs_hba *hba = dev_get_drvdata(dev);
 
-	return snprintf(buf, PAGE_SIZE, "%d\n", hba->clk_scaling.is_allowed);
+	return snprintf(buf, PAGE_SIZE, "%d\n", hba->clk_scaling.is_enabled);
 }
 
 static ssize_t ufshcd_clkscale_enable_store(struct device *dev,
@@ -1555,7 +1562,7 @@ static ssize_t ufshcd_clkscale_enable_store(struct device *dev,
 		return -EINVAL;
 
 	value = !!value;
-	if (value == hba->clk_scaling.is_allowed)
+	if (value == hba->clk_scaling.is_enabled)
 		goto out;
 
 	pm_runtime_get_sync(hba->dev);
@@ -1564,7 +1571,7 @@ static ssize_t ufshcd_clkscale_enable_store(struct device *dev,
 	cancel_work_sync(&hba->clk_scaling.suspend_work);
 	cancel_work_sync(&hba->clk_scaling.resume_work);
 
-	hba->clk_scaling.is_allowed = value;
+	hba->clk_scaling.is_enabled = value;
 
 	if (value) {
 		ufshcd_resume_clkscaling(hba);
@@ -1902,8 +1909,6 @@ static void ufshcd_init_clk_scaling(struct ufs_hba *hba)
 	snprintf(wq_name, sizeof(wq_name), "ufs_clkscaling_%d",
 		 hba->host->host_no);
 	hba->clk_scaling.workq = create_singlethread_workqueue(wq_name);
-
-	ufshcd_clkscaling_init_sysfs(hba);
 }
 
 static void ufshcd_exit_clk_scaling(struct ufs_hba *hba)
@@ -1911,6 +1916,8 @@ static void ufshcd_exit_clk_scaling(struct ufs_hba *hba)
 	if (!ufshcd_is_clkscaling_supported(hba))
 		return;
 
+	if (hba->clk_scaling.enable_attr.attr.name)
+		device_remove_file(hba->dev, &hba->clk_scaling.enable_attr);
 	destroy_workqueue(hba->clk_scaling.workq);
 	ufshcd_devfreq_remove(hba);
 }
@@ -1975,7 +1982,7 @@ static void ufshcd_clk_scaling_start_busy(struct ufs_hba *hba)
 	if (!hba->clk_scaling.active_reqs++)
 		queue_resume_work = true;
 
-	if (!hba->clk_scaling.is_allowed || hba->pm_op_in_progress)
+	if (!hba->clk_scaling.is_enabled || hba->pm_op_in_progress)
 		return;
 
 	if (queue_resume_work)
@@ -5093,7 +5100,8 @@ static void __ufshcd_transfer_req_compl(struct ufs_hba *hba,
 				update_scaling = true;
 			}
 		}
-		if (ufshcd_is_clkscaling_supported(hba) && update_scaling)
+		if (ufshcd_is_clkscaling_supported(hba) && update_scaling &&
+		    hba->clk_scaling.active_reqs > 0)
 			hba->clk_scaling.active_reqs--;
 	}
 
@@ -5759,18 +5767,24 @@ static void ufshcd_err_handling_prepare(struct ufs_hba *hba)
 		ufshcd_vops_resume(hba, pm_op);
 	} else {
 		ufshcd_hold(hba, false);
-		if (hba->clk_scaling.is_allowed) {
+		if (hba->clk_scaling.is_enabled) {
 			cancel_work_sync(&hba->clk_scaling.suspend_work);
 			cancel_work_sync(&hba->clk_scaling.resume_work);
 			ufshcd_suspend_clkscaling(hba);
 		}
+		down_write(&hba->clk_scaling_lock);
+		hba->clk_scaling.is_allowed = false;
+		up_write(&hba->clk_scaling_lock);
 	}
 }
 
 static void ufshcd_err_handling_unprepare(struct ufs_hba *hba)
 {
 	ufshcd_release(hba);
-	if (hba->clk_scaling.is_allowed)
+	down_write(&hba->clk_scaling_lock);
+	hba->clk_scaling.is_allowed = true;
+	up_write(&hba->clk_scaling_lock);
+	if (hba->clk_scaling.is_enabled)
 		ufshcd_resume_clkscaling(hba);
 	pm_runtime_put(hba->dev);
 }
@@ -7750,12 +7764,14 @@ static int ufshcd_add_lus(struct ufs_hba *hba)
 			sizeof(struct ufs_pa_layer_attr));
 		hba->clk_scaling.saved_pwr_info.is_valid = true;
 		if (!hba->devfreq) {
+			hba->clk_scaling.is_allowed = true;
 			ret = ufshcd_devfreq_init(hba);
 			if (ret)
 				goto out;
-		}
 
-		hba->clk_scaling.is_allowed = true;
+			hba->clk_scaling.is_enabled = true;
+			ufshcd_clkscaling_init_sysfs(hba);
+		}
 	}
 
 	ufs_bsg_probe(hba);
@@ -8672,11 +8688,14 @@ static int ufshcd_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
 	ufshcd_hold(hba, false);
 	hba->clk_gating.is_suspended = true;
 
-	if (hba->clk_scaling.is_allowed) {
+	if (hba->clk_scaling.is_enabled) {
 		cancel_work_sync(&hba->clk_scaling.suspend_work);
 		cancel_work_sync(&hba->clk_scaling.resume_work);
 		ufshcd_suspend_clkscaling(hba);
 	}
+	down_write(&hba->clk_scaling_lock);
+	hba->clk_scaling.is_allowed = false;
+	up_write(&hba->clk_scaling_lock);
 
 	if (req_dev_pwr_mode == UFS_ACTIVE_PWR_MODE &&
 			req_link_state == UIC_LINK_ACTIVE_STATE) {
@@ -8773,8 +8792,6 @@ static int ufshcd_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
 	goto out;
 
 set_link_active:
-	if (hba->clk_scaling.is_allowed)
-		ufshcd_resume_clkscaling(hba);
 	ufshcd_vreg_set_hpm(hba);
 	/*
 	 * Device hardware reset is required to exit DeepSleep. Also, for
@@ -8798,7 +8815,10 @@ static int ufshcd_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
 	if (!ufshcd_set_dev_pwr_mode(hba, UFS_ACTIVE_PWR_MODE))
 		ufshcd_disable_auto_bkops(hba);
 enable_gating:
-	if (hba->clk_scaling.is_allowed)
+	down_write(&hba->clk_scaling_lock);
+	hba->clk_scaling.is_allowed = true;
+	up_write(&hba->clk_scaling_lock);
+	if (hba->clk_scaling.is_enabled)
 		ufshcd_resume_clkscaling(hba);
 	hba->clk_gating.is_suspended = false;
 	hba->dev_info.b_rpm_dev_flush_capable = false;
@@ -8901,7 +8921,10 @@ static int ufshcd_resume(struct ufs_hba *hba, enum ufs_pm_op pm_op)
 
 	hba->clk_gating.is_suspended = false;
 
-	if (hba->clk_scaling.is_allowed)
+	down_write(&hba->clk_scaling_lock);
+	hba->clk_scaling.is_allowed = true;
+	up_write(&hba->clk_scaling_lock);
+	if (hba->clk_scaling.is_enabled)
 		ufshcd_resume_clkscaling(hba);
 
 	/* Enable Auto-Hibernate if configured */
@@ -8925,8 +8948,6 @@ static int ufshcd_resume(struct ufs_hba *hba, enum ufs_pm_op pm_op)
 	ufshcd_vreg_set_lpm(hba);
 disable_irq_and_vops_clks:
 	ufshcd_disable_irq(hba);
-	if (hba->clk_scaling.is_allowed)
-		ufshcd_suspend_clkscaling(hba);
 	ufshcd_setup_clocks(hba, false);
 	if (ufshcd_is_clkgating_allowed(hba)) {
 		hba->clk_gating.state = CLKS_OFF;
@@ -9153,8 +9174,6 @@ void ufshcd_remove(struct ufs_hba *hba)
 
 	ufshcd_exit_clk_scaling(hba);
 	ufshcd_exit_clk_gating(hba);
-	if (ufshcd_is_clkscaling_supported(hba))
-		device_remove_file(hba->dev, &hba->clk_scaling.enable_attr);
 	ufshcd_hba_exit(hba);
 }
 EXPORT_SYMBOL_GPL(ufshcd_remove);
diff --git a/drivers/scsi/ufs/ufshcd.h b/drivers/scsi/ufs/ufshcd.h
index 85f9d0f..d553e46 100644
--- a/drivers/scsi/ufs/ufshcd.h
+++ b/drivers/scsi/ufs/ufshcd.h
@@ -419,7 +419,10 @@ struct ufs_saved_pwr_info {
  * @suspend_work: worker to suspend devfreq
  * @resume_work: worker to resume devfreq
  * @min_gear: lowest HS gear to scale down to
- * @is_allowed: tracks if scaling is currently allowed or not
+ * @is_enabled: tracks if scaling is currently enabled or not, controlled by
+		clkscale_enable sysfs node
+ * @is_allowed: tracks if scaling is currently allowed or not, used to block
+		clock scaling which is not invoked from devfreq governor
  * @is_busy_started: tracks if busy period has started or not
  * @is_suspended: tracks if devfreq is suspended or not
  */
@@ -434,6 +437,7 @@ struct ufs_clk_scaling {
 	struct work_struct suspend_work;
 	struct work_struct resume_work;
 	u32 min_gear;
+	bool is_enabled;
 	bool is_allowed;
 	bool is_busy_started;
 	bool is_suspended;
-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project.

[PATCH v10 2/3] scsi: ufs: Refactor ufshcd_init/exit_clk_scaling/gating()

[Can Guo]

ufshcd_hba_exit() is always called after ufshcd_exit_clk_scaling() and
ufshcd_exit_clk_gating(), so move ufshcd_exit_clk_scaling/gating() to
ufshcd_hba_exit(). Meanwhile, add dedicated funcs to init and remove
sysfs nodes of clock scaling/gating to make the code more readable.
Overall functionality remains same.

Signed-off-by: Can Guo <cang@codeaurora.org>
---
 drivers/scsi/ufs/ufshcd.c | 130 +++++++++++++++++++++++++---------------------
 drivers/scsi/ufs/ufshcd.h |   4 ++
 2 files changed, 74 insertions(+), 60 deletions(-)

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index ba62d84..df046bd 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -1589,7 +1589,7 @@ static ssize_t ufshcd_clkscale_enable_store(struct device *dev,
 	return count;
 }
 
-static void ufshcd_clkscaling_init_sysfs(struct ufs_hba *hba)
+static void ufshcd_init_clk_scaling_sysfs(struct ufs_hba *hba)
 {
 	hba->clk_scaling.enable_attr.show = ufshcd_clkscale_enable_show;
 	hba->clk_scaling.enable_attr.store = ufshcd_clkscale_enable_store;
@@ -1600,6 +1600,42 @@ static void ufshcd_clkscaling_init_sysfs(struct ufs_hba *hba)
 		dev_err(hba->dev, "Failed to create sysfs for clkscale_enable\n");
 }
 
+static void ufshcd_remove_clk_scaling_sysfs(struct ufs_hba *hba)
+{
+	if (hba->clk_scaling.enable_attr.attr.name)
+		device_remove_file(hba->dev, &hba->clk_scaling.enable_attr);
+}
+
+static void ufshcd_init_clk_scaling(struct ufs_hba *hba)
+{
+	char wq_name[sizeof("ufs_clkscaling_00")];
+
+	if (!ufshcd_is_clkscaling_supported(hba))
+		return;
+
+	INIT_WORK(&hba->clk_scaling.suspend_work,
+		  ufshcd_clk_scaling_suspend_work);
+	INIT_WORK(&hba->clk_scaling.resume_work,
+		  ufshcd_clk_scaling_resume_work);
+
+	snprintf(wq_name, sizeof(wq_name), "ufs_clkscaling_%d",
+		 hba->host->host_no);
+	hba->clk_scaling.workq = create_singlethread_workqueue(wq_name);
+
+	hba->clk_scaling.is_initialized = true;
+}
+
+static void ufshcd_exit_clk_scaling(struct ufs_hba *hba)
+{
+	if (!hba->clk_scaling.is_initialized)
+		return;
+
+	ufshcd_remove_clk_scaling_sysfs(hba);
+	destroy_workqueue(hba->clk_scaling.workq);
+	ufshcd_devfreq_remove(hba);
+	hba->clk_scaling.is_initialized = false;
+}
+
 static void ufshcd_ungate_work(struct work_struct *work)
 {
 	int ret;
@@ -1891,35 +1927,31 @@ static ssize_t ufshcd_clkgate_enable_store(struct device *dev,
 	return count;
 }
 
-static void ufshcd_init_clk_scaling(struct ufs_hba *hba)
+static void ufshcd_init_clk_gating_sysfs(struct ufs_hba *hba)
 {
-	char wq_name[sizeof("ufs_clkscaling_00")];
-
-	if (!ufshcd_is_clkscaling_supported(hba))
-		return;
-
-	if (!hba->clk_scaling.min_gear)
-		hba->clk_scaling.min_gear = UFS_HS_G1;
-
-	INIT_WORK(&hba->clk_scaling.suspend_work,
-		  ufshcd_clk_scaling_suspend_work);
-	INIT_WORK(&hba->clk_scaling.resume_work,
-		  ufshcd_clk_scaling_resume_work);
+	hba->clk_gating.delay_attr.show = ufshcd_clkgate_delay_show;
+	hba->clk_gating.delay_attr.store = ufshcd_clkgate_delay_store;
+	sysfs_attr_init(&hba->clk_gating.delay_attr.attr);
+	hba->clk_gating.delay_attr.attr.name = "clkgate_delay_ms";
+	hba->clk_gating.delay_attr.attr.mode = 0644;
+	if (device_create_file(hba->dev, &hba->clk_gating.delay_attr))
+		dev_err(hba->dev, "Failed to create sysfs for clkgate_delay\n");
 
-	snprintf(wq_name, sizeof(wq_name), "ufs_clkscaling_%d",
-		 hba->host->host_no);
-	hba->clk_scaling.workq = create_singlethread_workqueue(wq_name);
+	hba->clk_gating.enable_attr.show = ufshcd_clkgate_enable_show;
+	hba->clk_gating.enable_attr.store = ufshcd_clkgate_enable_store;
+	sysfs_attr_init(&hba->clk_gating.enable_attr.attr);
+	hba->clk_gating.enable_attr.attr.name = "clkgate_enable";
+	hba->clk_gating.enable_attr.attr.mode = 0644;
+	if (device_create_file(hba->dev, &hba->clk_gating.enable_attr))
+		dev_err(hba->dev, "Failed to create sysfs for clkgate_enable\n");
 }
 
-static void ufshcd_exit_clk_scaling(struct ufs_hba *hba)
+static void ufshcd_remove_clk_gating_sysfs(struct ufs_hba *hba)
 {
-	if (!ufshcd_is_clkscaling_supported(hba))
-		return;
-
-	if (hba->clk_scaling.enable_attr.attr.name)
-		device_remove_file(hba->dev, &hba->clk_scaling.enable_attr);
-	destroy_workqueue(hba->clk_scaling.workq);
-	ufshcd_devfreq_remove(hba);
+	if (hba->clk_gating.delay_attr.attr.name)
+		device_remove_file(hba->dev, &hba->clk_gating.delay_attr);
+	if (hba->clk_gating.enable_attr.attr.name)
+		device_remove_file(hba->dev, &hba->clk_gating.enable_attr);
 }
 
 static void ufshcd_init_clk_gating(struct ufs_hba *hba)
@@ -1940,34 +1972,21 @@ static void ufshcd_init_clk_gating(struct ufs_hba *hba)
 	hba->clk_gating.clk_gating_workq = alloc_ordered_workqueue(wq_name,
 					WQ_MEM_RECLAIM | WQ_HIGHPRI);
 
-	hba->clk_gating.is_enabled = true;
+	ufshcd_init_clk_gating_sysfs(hba);
 
-	hba->clk_gating.delay_attr.show = ufshcd_clkgate_delay_show;
-	hba->clk_gating.delay_attr.store = ufshcd_clkgate_delay_store;
-	sysfs_attr_init(&hba->clk_gating.delay_attr.attr);
-	hba->clk_gating.delay_attr.attr.name = "clkgate_delay_ms";
-	hba->clk_gating.delay_attr.attr.mode = 0644;
-	if (device_create_file(hba->dev, &hba->clk_gating.delay_attr))
-		dev_err(hba->dev, "Failed to create sysfs for clkgate_delay\n");
-
-	hba->clk_gating.enable_attr.show = ufshcd_clkgate_enable_show;
-	hba->clk_gating.enable_attr.store = ufshcd_clkgate_enable_store;
-	sysfs_attr_init(&hba->clk_gating.enable_attr.attr);
-	hba->clk_gating.enable_attr.attr.name = "clkgate_enable";
-	hba->clk_gating.enable_attr.attr.mode = 0644;
-	if (device_create_file(hba->dev, &hba->clk_gating.enable_attr))
-		dev_err(hba->dev, "Failed to create sysfs for clkgate_enable\n");
+	hba->clk_gating.is_enabled = true;
+	hba->clk_gating.is_initialized = true;
 }
 
 static void ufshcd_exit_clk_gating(struct ufs_hba *hba)
 {
-	if (!ufshcd_is_clkgating_allowed(hba))
+	if (!hba->clk_gating.is_initialized)
 		return;
-	device_remove_file(hba->dev, &hba->clk_gating.delay_attr);
-	device_remove_file(hba->dev, &hba->clk_gating.enable_attr);
+	ufshcd_remove_clk_gating_sysfs(hba);
 	cancel_work_sync(&hba->clk_gating.ungate_work);
 	cancel_delayed_work_sync(&hba->clk_gating.gate_work);
 	destroy_workqueue(hba->clk_gating.clk_gating_workq);
+	hba->clk_gating.is_initialized = false;
 }
 
 /* Must be called with host lock acquired */
@@ -7770,7 +7789,7 @@ static int ufshcd_add_lus(struct ufs_hba *hba)
 				goto out;
 
 			hba->clk_scaling.is_enabled = true;
-			ufshcd_clkscaling_init_sysfs(hba);
+			ufshcd_init_clk_scaling_sysfs(hba);
 		}
 	}
 
@@ -7958,7 +7977,6 @@ static void ufshcd_async_scan(void *data, async_cookie_t cookie)
 	 */
 	if (ret) {
 		pm_runtime_put_sync(hba->dev);
-		ufshcd_exit_clk_scaling(hba);
 		ufshcd_hba_exit(hba);
 	} else {
 		ufshcd_clear_ua_wluns(hba);
@@ -8388,12 +8406,12 @@ static int ufshcd_hba_init(struct ufs_hba *hba)
 static void ufshcd_hba_exit(struct ufs_hba *hba)
 {
 	if (hba->is_powered) {
+		ufshcd_exit_clk_scaling(hba);
+		ufshcd_exit_clk_gating(hba);
+		if (hba->eh_wq)
+			destroy_workqueue(hba->eh_wq);
 		ufshcd_variant_hba_exit(hba);
 		ufshcd_setup_vreg(hba, false);
-		ufshcd_suspend_clkscaling(hba);
-		if (ufshcd_is_clkscaling_supported(hba))
-			if (hba->devfreq)
-				ufshcd_suspend_clkscaling(hba);
 		ufshcd_setup_clocks(hba, false);
 		ufshcd_setup_hba_vreg(hba, false);
 		hba->is_powered = false;
@@ -9167,13 +9185,9 @@ void ufshcd_remove(struct ufs_hba *hba)
 	blk_mq_free_tag_set(&hba->tmf_tag_set);
 	blk_cleanup_queue(hba->cmd_queue);
 	scsi_remove_host(hba->host);
-	destroy_workqueue(hba->eh_wq);
 	/* disable interrupts */
 	ufshcd_disable_intr(hba, hba->intr_mask);
 	ufshcd_hba_stop(hba);
-
-	ufshcd_exit_clk_scaling(hba);
-	ufshcd_exit_clk_gating(hba);
 	ufshcd_hba_exit(hba);
 }
 EXPORT_SYMBOL_GPL(ufshcd_remove);
@@ -9374,7 +9388,7 @@ int ufshcd_init(struct ufs_hba *hba, void __iomem *mmio_base, unsigned int irq)
 	err = devm_request_irq(dev, irq, ufshcd_intr, IRQF_SHARED, UFSHCD, hba);
 	if (err) {
 		dev_err(hba->dev, "request irq failed\n");
-		goto exit_gating;
+		goto out_disable;
 	} else {
 		hba->is_irq_enabled = true;
 	}
@@ -9382,7 +9396,7 @@ int ufshcd_init(struct ufs_hba *hba, void __iomem *mmio_base, unsigned int irq)
 	err = scsi_add_host(host, hba->dev);
 	if (err) {
 		dev_err(hba->dev, "scsi_add_host failed\n");
-		goto exit_gating;
+		goto out_disable;
 	}
 
 	hba->cmd_queue = blk_mq_init_queue(&hba->host->tag_set);
@@ -9465,10 +9479,6 @@ int ufshcd_init(struct ufs_hba *hba, void __iomem *mmio_base, unsigned int irq)
 	blk_cleanup_queue(hba->cmd_queue);
 out_remove_scsi_host:
 	scsi_remove_host(hba->host);
-exit_gating:
-	ufshcd_exit_clk_scaling(hba);
-	ufshcd_exit_clk_gating(hba);
-	destroy_workqueue(hba->eh_wq);
 out_disable:
 	hba->is_irq_enabled = false;
 	ufshcd_hba_exit(hba);
diff --git a/drivers/scsi/ufs/ufshcd.h b/drivers/scsi/ufs/ufshcd.h
index d553e46..bb45f5d 100644
--- a/drivers/scsi/ufs/ufshcd.h
+++ b/drivers/scsi/ufs/ufshcd.h
@@ -383,6 +383,7 @@ enum clk_gating_state {
  * @delay_attr: sysfs attribute to control delay_attr
  * @enable_attr: sysfs attribute to enable/disable clock gating
  * @is_enabled: Indicates the current status of clock gating
+ * @is_initialized: Indicates whether clock gating is initialized or not
  * @active_reqs: number of requests that are pending and should be waited for
  * completion before gating clocks.
  */
@@ -395,6 +396,7 @@ struct ufs_clk_gating {
 	struct device_attribute delay_attr;
 	struct device_attribute enable_attr;
 	bool is_enabled;
+	bool is_initialized;
 	int active_reqs;
 	struct workqueue_struct *clk_gating_workq;
 };
@@ -423,6 +425,7 @@ struct ufs_saved_pwr_info {
 		clkscale_enable sysfs node
  * @is_allowed: tracks if scaling is currently allowed or not, used to block
 		clock scaling which is not invoked from devfreq governor
+ * @is_initialized: Indicates whether clock scaling is initialized or not
  * @is_busy_started: tracks if busy period has started or not
  * @is_suspended: tracks if devfreq is suspended or not
  */
@@ -439,6 +442,7 @@ struct ufs_clk_scaling {
 	u32 min_gear;
 	bool is_enabled;
 	bool is_allowed;
+	bool is_initialized;
 	bool is_busy_started;
 	bool is_suspended;
 };
-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project.

[PATCH v10 3/3] scsi: ufs: Revert "Make sure clk scaling happens only when HBA is runtime ACTIVE"

[Can Guo]

Commit 73cc291c27024 ("Make sure clk scaling happens only when HBA is
runtime ACTIVE") is no longer needed since commit f7a42540928a8 ("scsi:
ufs: Protect some contexts from unexpected clock scaling") is a more
mature fix to protect UFS LLD stability from clock scaling invoked through
sysfs nodes by users.

Reviewed-by: Stanley Chu <stanley.chu@mediatek.com>
Signed-off-by: Can Guo <cang@codeaurora.org>
---
 drivers/scsi/ufs/ufshcd.c | 7 -------
 1 file changed, 7 deletions(-)

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index df046bd..8ec41ea 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -1355,15 +1355,8 @@ static int ufshcd_devfreq_target(struct device *dev,
 	}
 	spin_unlock_irqrestore(hba->host->host_lock, irq_flags);
 
-	pm_runtime_get_noresume(hba->dev);
-	if (!pm_runtime_active(hba->dev)) {
-		pm_runtime_put_noidle(hba->dev);
-		ret = -EAGAIN;
-		goto out;
-	}
 	start = ktime_get();
 	ret = ufshcd_devfreq_scale(hba, scale_up);
-	pm_runtime_put(hba->dev);
 
 	trace_ufshcd_profile_clk_scaling(dev_name(hba->dev),
 		(scale_up ? "up" : "down"),
-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project.

Re: [PATCH v10 1/3] scsi: ufs: Protect some contexts from unexpected clock scaling

[Stanley Chu]

Hi Can,

On Tue, 2021-01-19 at 03:52 -0800, Can Guo wrote:
> In contexts like suspend, shutdown and error handling, we need to suspend
> devfreq to make sure these contexts won't be disturbed by clock scaling.
> However, suspending devfreq is not enough since users can still trigger a
> clock scaling by manipulating the devfreq sysfs nodes like min/max_freq and
> governor even after devfreq is suspended. Moreover, mere suspending devfreq
> cannot synchroinze a clock scaling which has already been invoked through
> these sysfs nodes. Add one more flag in struct clk_scaling and wrap the
> entire func ufshcd_devfreq_scale() with the clk_scaling_lock, so that we
> can use this flag and clk_scaling_lock to control and synchronize clock
> scaling invoked through devfreq sysfs nodes.
> 
> Signed-off-by: Can Guo <cang@codeaurora.org>
> ---
>  drivers/scsi/ufs/ufshcd.c | 83 +++++++++++++++++++++++++++++------------------
>  drivers/scsi/ufs/ufshcd.h |  6 +++-
>  2 files changed, 56 insertions(+), 33 deletions(-)
> 
> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> index 53fd59c..ba62d84 100644
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -1201,19 +1201,30 @@ static int ufshcd_clock_scaling_prepare(struct ufs_hba *hba)
>  	 */
>  	ufshcd_scsi_block_requests(hba);
>  	down_write(&hba->clk_scaling_lock);
> -	if (ufshcd_wait_for_doorbell_clr(hba, DOORBELL_CLR_TOUT_US)) {
> +
> +	if (!hba->clk_scaling.is_allowed ||
> +	    ufshcd_wait_for_doorbell_clr(hba, DOORBELL_CLR_TOUT_US)) {
>  		ret = -EBUSY;
>  		up_write(&hba->clk_scaling_lock);
>  		ufshcd_scsi_unblock_requests(hba);
> +		goto out;
>  	}
>  
> +	/* let's not get into low power until clock scaling is completed */
> +	ufshcd_hold(hba, false);
> +
> +out:
>  	return ret;
>  }
>  
> -static void ufshcd_clock_scaling_unprepare(struct ufs_hba *hba)
> +static void ufshcd_clock_scaling_unprepare(struct ufs_hba *hba, bool writelock)
>  {
> -	up_write(&hba->clk_scaling_lock);
> +	if (writelock)
> +		up_write(&hba->clk_scaling_lock);
> +	else
> +		up_read(&hba->clk_scaling_lock);
>  	ufshcd_scsi_unblock_requests(hba);
> +	ufshcd_release(hba);
>  }
>  
>  /**
> @@ -1228,13 +1239,11 @@ static void ufshcd_clock_scaling_unprepare(struct ufs_hba *hba)
>  static int ufshcd_devfreq_scale(struct ufs_hba *hba, bool scale_up)
>  {
>  	int ret = 0;
> -
> -	/* let's not get into low power until clock scaling is completed */
> -	ufshcd_hold(hba, false);
> +	bool is_writelock = true;
>  
>  	ret = ufshcd_clock_scaling_prepare(hba);
>  	if (ret)
> -		goto out;
> +		return ret;
>  
>  	/* scale down the gear before scaling down clocks */
>  	if (!scale_up) {
> @@ -1260,14 +1269,12 @@ static int ufshcd_devfreq_scale(struct ufs_hba *hba, bool scale_up)
>  	}
>  
>  	/* Enable Write Booster if we have scaled up else disable it */
> -	up_write(&hba->clk_scaling_lock);
> +	downgrade_write(&hba->clk_scaling_lock);
> +	is_writelock = false;
>  	ufshcd_wb_ctrl(hba, scale_up);
> -	down_write(&hba->clk_scaling_lock);
>  
>  out_unprepare:
> -	ufshcd_clock_scaling_unprepare(hba);
> -out:
> -	ufshcd_release(hba);
> +	ufshcd_clock_scaling_unprepare(hba, is_writelock);
>  	return ret;
>  }
>  
> @@ -1541,7 +1548,7 @@ static ssize_t ufshcd_clkscale_enable_show(struct device *dev,
>  {
>  	struct ufs_hba *hba = dev_get_drvdata(dev);
>  
> -	return snprintf(buf, PAGE_SIZE, "%d\n", hba->clk_scaling.is_allowed);
> +	return snprintf(buf, PAGE_SIZE, "%d\n", hba->clk_scaling.is_enabled);
>  }
>  
>  static ssize_t ufshcd_clkscale_enable_store(struct device *dev,
> @@ -1555,7 +1562,7 @@ static ssize_t ufshcd_clkscale_enable_store(struct device *dev,
>  		return -EINVAL;
>  
>  	value = !!value;
> -	if (value == hba->clk_scaling.is_allowed)
> +	if (value == hba->clk_scaling.is_enabled)
>  		goto out;
>  
>  	pm_runtime_get_sync(hba->dev);
> @@ -1564,7 +1571,7 @@ static ssize_t ufshcd_clkscale_enable_store(struct device *dev,
>  	cancel_work_sync(&hba->clk_scaling.suspend_work);
>  	cancel_work_sync(&hba->clk_scaling.resume_work);
>  
> -	hba->clk_scaling.is_allowed = value;
> +	hba->clk_scaling.is_enabled = value;
>  
>  	if (value) {
>  		ufshcd_resume_clkscaling(hba);
> @@ -1902,8 +1909,6 @@ static void ufshcd_init_clk_scaling(struct ufs_hba *hba)
>  	snprintf(wq_name, sizeof(wq_name), "ufs_clkscaling_%d",
>  		 hba->host->host_no);
>  	hba->clk_scaling.workq = create_singlethread_workqueue(wq_name);
> -
> -	ufshcd_clkscaling_init_sysfs(hba);
>  }
>  
>  static void ufshcd_exit_clk_scaling(struct ufs_hba *hba)
> @@ -1911,6 +1916,8 @@ static void ufshcd_exit_clk_scaling(struct ufs_hba *hba)
>  	if (!ufshcd_is_clkscaling_supported(hba))
>  		return;
>  
> +	if (hba->clk_scaling.enable_attr.attr.name)
> +		device_remove_file(hba->dev, &hba->clk_scaling.enable_attr);
>  	destroy_workqueue(hba->clk_scaling.workq);
>  	ufshcd_devfreq_remove(hba);
>  }
> @@ -1975,7 +1982,7 @@ static void ufshcd_clk_scaling_start_busy(struct ufs_hba *hba)
>  	if (!hba->clk_scaling.active_reqs++)
>  		queue_resume_work = true;
>  
> -	if (!hba->clk_scaling.is_allowed || hba->pm_op_in_progress)
> +	if (!hba->clk_scaling.is_enabled || hba->pm_op_in_progress)
>  		return;
>  
>  	if (queue_resume_work)
> @@ -5093,7 +5100,8 @@ static void __ufshcd_transfer_req_compl(struct ufs_hba *hba,
>  				update_scaling = true;
>  			}
>  		}
> -		if (ufshcd_is_clkscaling_supported(hba) && update_scaling)
> +		if (ufshcd_is_clkscaling_supported(hba) && update_scaling &&

> +		    hba->clk_scaling.active_reqs > 0)
Do we need to check hba->clk_scaling.active_reqs here?

if hba->clk_scaling.active_reqs is possibly decreased to negative value
here, then there may be something to be fixed?

Otherwise this patch looks good to me.

Thanks,
Stanley Chu

>  			hba->clk_scaling.active_reqs--;
>  	}
>  
> @@ -5759,18 +5767,24 @@ static void ufshcd_err_handling_prepare(struct ufs_hba *hba)
>  		ufshcd_vops_resume(hba, pm_op);
>  	} else {
>  		ufshcd_hold(hba, false);
> -		if (hba->clk_scaling.is_allowed) {
> +		if (hba->clk_scaling.is_enabled) {
>  			cancel_work_sync(&hba->clk_scaling.suspend_work);
>  			cancel_work_sync(&hba->clk_scaling.resume_work);
>  			ufshcd_suspend_clkscaling(hba);
>  		}
> +		down_write(&hba->clk_scaling_lock);
> +		hba->clk_scaling.is_allowed = false;
> +		up_write(&hba->clk_scaling_lock);
>  	}
>  }
>  
>  static void ufshcd_err_handling_unprepare(struct ufs_hba *hba)
>  {
>  	ufshcd_release(hba);
> -	if (hba->clk_scaling.is_allowed)
> +	down_write(&hba->clk_scaling_lock);
> +	hba->clk_scaling.is_allowed = true;
> +	up_write(&hba->clk_scaling_lock);
> +	if (hba->clk_scaling.is_enabled)
>  		ufshcd_resume_clkscaling(hba);
>  	pm_runtime_put(hba->dev);
>  }
> @@ -7750,12 +7764,14 @@ static int ufshcd_add_lus(struct ufs_hba *hba)
>  			sizeof(struct ufs_pa_layer_attr));
>  		hba->clk_scaling.saved_pwr_info.is_valid = true;
>  		if (!hba->devfreq) {
> +			hba->clk_scaling.is_allowed = true;
>  			ret = ufshcd_devfreq_init(hba);
>  			if (ret)
>  				goto out;
> -		}
>  
> -		hba->clk_scaling.is_allowed = true;
> +			hba->clk_scaling.is_enabled = true;
> +			ufshcd_clkscaling_init_sysfs(hba);
> +		}
>  	}
>  
>  	ufs_bsg_probe(hba);
> @@ -8672,11 +8688,14 @@ static int ufshcd_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
>  	ufshcd_hold(hba, false);
>  	hba->clk_gating.is_suspended = true;
>  
> -	if (hba->clk_scaling.is_allowed) {
> +	if (hba->clk_scaling.is_enabled) {
>  		cancel_work_sync(&hba->clk_scaling.suspend_work);
>  		cancel_work_sync(&hba->clk_scaling.resume_work);
>  		ufshcd_suspend_clkscaling(hba);
>  	}
> +	down_write(&hba->clk_scaling_lock);
> +	hba->clk_scaling.is_allowed = false;
> +	up_write(&hba->clk_scaling_lock);
>  
>  	if (req_dev_pwr_mode == UFS_ACTIVE_PWR_MODE &&
>  			req_link_state == UIC_LINK_ACTIVE_STATE) {
> @@ -8773,8 +8792,6 @@ static int ufshcd_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
>  	goto out;
>  
>  set_link_active:
> -	if (hba->clk_scaling.is_allowed)
> -		ufshcd_resume_clkscaling(hba);
>  	ufshcd_vreg_set_hpm(hba);
>  	/*
>  	 * Device hardware reset is required to exit DeepSleep. Also, for
> @@ -8798,7 +8815,10 @@ static int ufshcd_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
>  	if (!ufshcd_set_dev_pwr_mode(hba, UFS_ACTIVE_PWR_MODE))
>  		ufshcd_disable_auto_bkops(hba);
>  enable_gating:
> -	if (hba->clk_scaling.is_allowed)
> +	down_write(&hba->clk_scaling_lock);
> +	hba->clk_scaling.is_allowed = true;
> +	up_write(&hba->clk_scaling_lock);
> +	if (hba->clk_scaling.is_enabled)
>  		ufshcd_resume_clkscaling(hba);
>  	hba->clk_gating.is_suspended = false;
>  	hba->dev_info.b_rpm_dev_flush_capable = false;
> @@ -8901,7 +8921,10 @@ static int ufshcd_resume(struct ufs_hba *hba, enum ufs_pm_op pm_op)
>  
>  	hba->clk_gating.is_suspended = false;
>  
> -	if (hba->clk_scaling.is_allowed)
> +	down_write(&hba->clk_scaling_lock);
> +	hba->clk_scaling.is_allowed = true;
> +	up_write(&hba->clk_scaling_lock);
> +	if (hba->clk_scaling.is_enabled)
>  		ufshcd_resume_clkscaling(hba);
>  
>  	/* Enable Auto-Hibernate if configured */
> @@ -8925,8 +8948,6 @@ static int ufshcd_resume(struct ufs_hba *hba, enum ufs_pm_op pm_op)
>  	ufshcd_vreg_set_lpm(hba);
>  disable_irq_and_vops_clks:
>  	ufshcd_disable_irq(hba);
> -	if (hba->clk_scaling.is_allowed)
> -		ufshcd_suspend_clkscaling(hba);
>  	ufshcd_setup_clocks(hba, false);
>  	if (ufshcd_is_clkgating_allowed(hba)) {
>  		hba->clk_gating.state = CLKS_OFF;
> @@ -9153,8 +9174,6 @@ void ufshcd_remove(struct ufs_hba *hba)
>  
>  	ufshcd_exit_clk_scaling(hba);
>  	ufshcd_exit_clk_gating(hba);
> -	if (ufshcd_is_clkscaling_supported(hba))
> -		device_remove_file(hba->dev, &hba->clk_scaling.enable_attr);
>  	ufshcd_hba_exit(hba);
>  }
>  EXPORT_SYMBOL_GPL(ufshcd_remove);
> diff --git a/drivers/scsi/ufs/ufshcd.h b/drivers/scsi/ufs/ufshcd.h
> index 85f9d0f..d553e46 100644
> --- a/drivers/scsi/ufs/ufshcd.h
> +++ b/drivers/scsi/ufs/ufshcd.h
> @@ -419,7 +419,10 @@ struct ufs_saved_pwr_info {
>   * @suspend_work: worker to suspend devfreq
>   * @resume_work: worker to resume devfreq
>   * @min_gear: lowest HS gear to scale down to
> - * @is_allowed: tracks if scaling is currently allowed or not
> + * @is_enabled: tracks if scaling is currently enabled or not, controlled by
> +		clkscale_enable sysfs node
> + * @is_allowed: tracks if scaling is currently allowed or not, used to block
> +		clock scaling which is not invoked from devfreq governor
>   * @is_busy_started: tracks if busy period has started or not
>   * @is_suspended: tracks if devfreq is suspended or not
>   */
> @@ -434,6 +437,7 @@ struct ufs_clk_scaling {
>  	struct work_struct suspend_work;
>  	struct work_struct resume_work;
>  	u32 min_gear;
> +	bool is_enabled;
>  	bool is_allowed;
>  	bool is_busy_started;
>  	bool is_suspended;

Re: [PATCH v10 2/3] scsi: ufs: Refactor ufshcd_init/exit_clk_scaling/gating()

[Stanley Chu]

Hi Can,

On Tue, 2021-01-19 at 03:53 -0800, Can Guo wrote:
> ufshcd_hba_exit() is always called after ufshcd_exit_clk_scaling() and
> ufshcd_exit_clk_gating(), so move ufshcd_exit_clk_scaling/gating() to
> ufshcd_hba_exit(). Meanwhile, add dedicated funcs to init and remove
> sysfs nodes of clock scaling/gating to make the code more readable.
> Overall functionality remains same.
> 
> Signed-off-by: Can Guo <cang@codeaurora.org>

Looks good to me.

BTW, FYI. this series has conflicts during the merge to the latest
for-next branch in Martin's tree.

Reviewed-by: Stanley Chu <stanley.chu@mediatek.com>

Re: [PATCH v10 1/3] scsi: ufs: Protect some contexts from unexpected clock scaling

[Can Guo]

On 2021-01-20 12:54, Stanley Chu wrote:
> Hi Can,
> 
> On Tue, 2021-01-19 at 03:52 -0800, Can Guo wrote:
>> In contexts like suspend, shutdown and error handling, we need to 
>> suspend
>> devfreq to make sure these contexts won't be disturbed by clock 
>> scaling.
>> However, suspending devfreq is not enough since users can still 
>> trigger a
>> clock scaling by manipulating the devfreq sysfs nodes like 
>> min/max_freq and
>> governor even after devfreq is suspended. Moreover, mere suspending 
>> devfreq
>> cannot synchroinze a clock scaling which has already been invoked 
>> through
>> these sysfs nodes. Add one more flag in struct clk_scaling and wrap 
>> the
>> entire func ufshcd_devfreq_scale() with the clk_scaling_lock, so that 
>> we
>> can use this flag and clk_scaling_lock to control and synchronize 
>> clock
>> scaling invoked through devfreq sysfs nodes.
>> 
>> Signed-off-by: Can Guo <cang@codeaurora.org>
>> ---
>>  drivers/scsi/ufs/ufshcd.c | 83 
>> +++++++++++++++++++++++++++++------------------
>>  drivers/scsi/ufs/ufshcd.h |  6 +++-
>>  2 files changed, 56 insertions(+), 33 deletions(-)
>> 
>> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
>> index 53fd59c..ba62d84 100644
>> --- a/drivers/scsi/ufs/ufshcd.c
>> +++ b/drivers/scsi/ufs/ufshcd.c
>> @@ -1201,19 +1201,30 @@ static int ufshcd_clock_scaling_prepare(struct 
>> ufs_hba *hba)
>>  	 */
>>  	ufshcd_scsi_block_requests(hba);
>>  	down_write(&hba->clk_scaling_lock);
>> -	if (ufshcd_wait_for_doorbell_clr(hba, DOORBELL_CLR_TOUT_US)) {
>> +
>> +	if (!hba->clk_scaling.is_allowed ||
>> +	    ufshcd_wait_for_doorbell_clr(hba, DOORBELL_CLR_TOUT_US)) {
>>  		ret = -EBUSY;
>>  		up_write(&hba->clk_scaling_lock);
>>  		ufshcd_scsi_unblock_requests(hba);
>> +		goto out;
>>  	}
>> 
>> +	/* let's not get into low power until clock scaling is completed */
>> +	ufshcd_hold(hba, false);
>> +
>> +out:
>>  	return ret;
>>  }
>> 
>> -static void ufshcd_clock_scaling_unprepare(struct ufs_hba *hba)
>> +static void ufshcd_clock_scaling_unprepare(struct ufs_hba *hba, bool 
>> writelock)
>>  {
>> -	up_write(&hba->clk_scaling_lock);
>> +	if (writelock)
>> +		up_write(&hba->clk_scaling_lock);
>> +	else
>> +		up_read(&hba->clk_scaling_lock);
>>  	ufshcd_scsi_unblock_requests(hba);
>> +	ufshcd_release(hba);
>>  }
>> 
>>  /**
>> @@ -1228,13 +1239,11 @@ static void 
>> ufshcd_clock_scaling_unprepare(struct ufs_hba *hba)
>>  static int ufshcd_devfreq_scale(struct ufs_hba *hba, bool scale_up)
>>  {
>>  	int ret = 0;
>> -
>> -	/* let's not get into low power until clock scaling is completed */
>> -	ufshcd_hold(hba, false);
>> +	bool is_writelock = true;
>> 
>>  	ret = ufshcd_clock_scaling_prepare(hba);
>>  	if (ret)
>> -		goto out;
>> +		return ret;
>> 
>>  	/* scale down the gear before scaling down clocks */
>>  	if (!scale_up) {
>> @@ -1260,14 +1269,12 @@ static int ufshcd_devfreq_scale(struct ufs_hba 
>> *hba, bool scale_up)
>>  	}
>> 
>>  	/* Enable Write Booster if we have scaled up else disable it */
>> -	up_write(&hba->clk_scaling_lock);
>> +	downgrade_write(&hba->clk_scaling_lock);
>> +	is_writelock = false;
>>  	ufshcd_wb_ctrl(hba, scale_up);
>> -	down_write(&hba->clk_scaling_lock);
>> 
>>  out_unprepare:
>> -	ufshcd_clock_scaling_unprepare(hba);
>> -out:
>> -	ufshcd_release(hba);
>> +	ufshcd_clock_scaling_unprepare(hba, is_writelock);
>>  	return ret;
>>  }
>> 
>> @@ -1541,7 +1548,7 @@ static ssize_t 
>> ufshcd_clkscale_enable_show(struct device *dev,
>>  {
>>  	struct ufs_hba *hba = dev_get_drvdata(dev);
>> 
>> -	return snprintf(buf, PAGE_SIZE, "%d\n", 
>> hba->clk_scaling.is_allowed);
>> +	return snprintf(buf, PAGE_SIZE, "%d\n", 
>> hba->clk_scaling.is_enabled);
>>  }
>> 
>>  static ssize_t ufshcd_clkscale_enable_store(struct device *dev,
>> @@ -1555,7 +1562,7 @@ static ssize_t 
>> ufshcd_clkscale_enable_store(struct device *dev,
>>  		return -EINVAL;
>> 
>>  	value = !!value;
>> -	if (value == hba->clk_scaling.is_allowed)
>> +	if (value == hba->clk_scaling.is_enabled)
>>  		goto out;
>> 
>>  	pm_runtime_get_sync(hba->dev);
>> @@ -1564,7 +1571,7 @@ static ssize_t 
>> ufshcd_clkscale_enable_store(struct device *dev,
>>  	cancel_work_sync(&hba->clk_scaling.suspend_work);
>>  	cancel_work_sync(&hba->clk_scaling.resume_work);
>> 
>> -	hba->clk_scaling.is_allowed = value;
>> +	hba->clk_scaling.is_enabled = value;
>> 
>>  	if (value) {
>>  		ufshcd_resume_clkscaling(hba);
>> @@ -1902,8 +1909,6 @@ static void ufshcd_init_clk_scaling(struct 
>> ufs_hba *hba)
>>  	snprintf(wq_name, sizeof(wq_name), "ufs_clkscaling_%d",
>>  		 hba->host->host_no);
>>  	hba->clk_scaling.workq = create_singlethread_workqueue(wq_name);
>> -
>> -	ufshcd_clkscaling_init_sysfs(hba);
>>  }
>> 
>>  static void ufshcd_exit_clk_scaling(struct ufs_hba *hba)
>> @@ -1911,6 +1916,8 @@ static void ufshcd_exit_clk_scaling(struct 
>> ufs_hba *hba)
>>  	if (!ufshcd_is_clkscaling_supported(hba))
>>  		return;
>> 
>> +	if (hba->clk_scaling.enable_attr.attr.name)
>> +		device_remove_file(hba->dev, &hba->clk_scaling.enable_attr);
>>  	destroy_workqueue(hba->clk_scaling.workq);
>>  	ufshcd_devfreq_remove(hba);
>>  }
>> @@ -1975,7 +1982,7 @@ static void ufshcd_clk_scaling_start_busy(struct 
>> ufs_hba *hba)
>>  	if (!hba->clk_scaling.active_reqs++)
>>  		queue_resume_work = true;
>> 
>> -	if (!hba->clk_scaling.is_allowed || hba->pm_op_in_progress)
>> +	if (!hba->clk_scaling.is_enabled || hba->pm_op_in_progress)
>>  		return;
>> 
>>  	if (queue_resume_work)
>> @@ -5093,7 +5100,8 @@ static void __ufshcd_transfer_req_compl(struct 
>> ufs_hba *hba,
>>  				update_scaling = true;
>>  			}
>>  		}
>> -		if (ufshcd_is_clkscaling_supported(hba) && update_scaling)
>> +		if (ufshcd_is_clkscaling_supported(hba) && update_scaling &&
> 
>> +		    hba->clk_scaling.active_reqs > 0)
> Do we need to check hba->clk_scaling.active_reqs here?
> 
> if hba->clk_scaling.active_reqs is possibly decreased to negative value
> here, then there may be something to be fixed?

No actual issue here, just want to be on the safe side.
Let me remove it in next version.

Thanks,
Can Guo.

> 
> Otherwise this patch looks good to me.
> 
> Thanks,
> Stanley Chu
> 
>>  			hba->clk_scaling.active_reqs--;
>>  	}
>> 
>> @@ -5759,18 +5767,24 @@ static void ufshcd_err_handling_prepare(struct 
>> ufs_hba *hba)
>>  		ufshcd_vops_resume(hba, pm_op);
>>  	} else {
>>  		ufshcd_hold(hba, false);
>> -		if (hba->clk_scaling.is_allowed) {
>> +		if (hba->clk_scaling.is_enabled) {
>>  			cancel_work_sync(&hba->clk_scaling.suspend_work);
>>  			cancel_work_sync(&hba->clk_scaling.resume_work);
>>  			ufshcd_suspend_clkscaling(hba);
>>  		}
>> +		down_write(&hba->clk_scaling_lock);
>> +		hba->clk_scaling.is_allowed = false;
>> +		up_write(&hba->clk_scaling_lock);
>>  	}
>>  }
>> 
>>  static void ufshcd_err_handling_unprepare(struct ufs_hba *hba)
>>  {
>>  	ufshcd_release(hba);
>> -	if (hba->clk_scaling.is_allowed)
>> +	down_write(&hba->clk_scaling_lock);
>> +	hba->clk_scaling.is_allowed = true;
>> +	up_write(&hba->clk_scaling_lock);
>> +	if (hba->clk_scaling.is_enabled)
>>  		ufshcd_resume_clkscaling(hba);
>>  	pm_runtime_put(hba->dev);
>>  }
>> @@ -7750,12 +7764,14 @@ static int ufshcd_add_lus(struct ufs_hba *hba)
>>  			sizeof(struct ufs_pa_layer_attr));
>>  		hba->clk_scaling.saved_pwr_info.is_valid = true;
>>  		if (!hba->devfreq) {
>> +			hba->clk_scaling.is_allowed = true;
>>  			ret = ufshcd_devfreq_init(hba);
>>  			if (ret)
>>  				goto out;
>> -		}
>> 
>> -		hba->clk_scaling.is_allowed = true;
>> +			hba->clk_scaling.is_enabled = true;
>> +			ufshcd_clkscaling_init_sysfs(hba);
>> +		}
>>  	}
>> 
>>  	ufs_bsg_probe(hba);
>> @@ -8672,11 +8688,14 @@ static int ufshcd_suspend(struct ufs_hba *hba, 
>> enum ufs_pm_op pm_op)
>>  	ufshcd_hold(hba, false);
>>  	hba->clk_gating.is_suspended = true;
>> 
>> -	if (hba->clk_scaling.is_allowed) {
>> +	if (hba->clk_scaling.is_enabled) {
>>  		cancel_work_sync(&hba->clk_scaling.suspend_work);
>>  		cancel_work_sync(&hba->clk_scaling.resume_work);
>>  		ufshcd_suspend_clkscaling(hba);
>>  	}
>> +	down_write(&hba->clk_scaling_lock);
>> +	hba->clk_scaling.is_allowed = false;
>> +	up_write(&hba->clk_scaling_lock);
>> 
>>  	if (req_dev_pwr_mode == UFS_ACTIVE_PWR_MODE &&
>>  			req_link_state == UIC_LINK_ACTIVE_STATE) {
>> @@ -8773,8 +8792,6 @@ static int ufshcd_suspend(struct ufs_hba *hba, 
>> enum ufs_pm_op pm_op)
>>  	goto out;
>> 
>>  set_link_active:
>> -	if (hba->clk_scaling.is_allowed)
>> -		ufshcd_resume_clkscaling(hba);
>>  	ufshcd_vreg_set_hpm(hba);
>>  	/*
>>  	 * Device hardware reset is required to exit DeepSleep. Also, for
>> @@ -8798,7 +8815,10 @@ static int ufshcd_suspend(struct ufs_hba *hba, 
>> enum ufs_pm_op pm_op)
>>  	if (!ufshcd_set_dev_pwr_mode(hba, UFS_ACTIVE_PWR_MODE))
>>  		ufshcd_disable_auto_bkops(hba);
>>  enable_gating:
>> -	if (hba->clk_scaling.is_allowed)
>> +	down_write(&hba->clk_scaling_lock);
>> +	hba->clk_scaling.is_allowed = true;
>> +	up_write(&hba->clk_scaling_lock);
>> +	if (hba->clk_scaling.is_enabled)
>>  		ufshcd_resume_clkscaling(hba);
>>  	hba->clk_gating.is_suspended = false;
>>  	hba->dev_info.b_rpm_dev_flush_capable = false;
>> @@ -8901,7 +8921,10 @@ static int ufshcd_resume(struct ufs_hba *hba, 
>> enum ufs_pm_op pm_op)
>> 
>>  	hba->clk_gating.is_suspended = false;
>> 
>> -	if (hba->clk_scaling.is_allowed)
>> +	down_write(&hba->clk_scaling_lock);
>> +	hba->clk_scaling.is_allowed = true;
>> +	up_write(&hba->clk_scaling_lock);
>> +	if (hba->clk_scaling.is_enabled)
>>  		ufshcd_resume_clkscaling(hba);
>> 
>>  	/* Enable Auto-Hibernate if configured */
>> @@ -8925,8 +8948,6 @@ static int ufshcd_resume(struct ufs_hba *hba, 
>> enum ufs_pm_op pm_op)
>>  	ufshcd_vreg_set_lpm(hba);
>>  disable_irq_and_vops_clks:
>>  	ufshcd_disable_irq(hba);
>> -	if (hba->clk_scaling.is_allowed)
>> -		ufshcd_suspend_clkscaling(hba);
>>  	ufshcd_setup_clocks(hba, false);
>>  	if (ufshcd_is_clkgating_allowed(hba)) {
>>  		hba->clk_gating.state = CLKS_OFF;
>> @@ -9153,8 +9174,6 @@ void ufshcd_remove(struct ufs_hba *hba)
>> 
>>  	ufshcd_exit_clk_scaling(hba);
>>  	ufshcd_exit_clk_gating(hba);
>> -	if (ufshcd_is_clkscaling_supported(hba))
>> -		device_remove_file(hba->dev, &hba->clk_scaling.enable_attr);
>>  	ufshcd_hba_exit(hba);
>>  }
>>  EXPORT_SYMBOL_GPL(ufshcd_remove);
>> diff --git a/drivers/scsi/ufs/ufshcd.h b/drivers/scsi/ufs/ufshcd.h
>> index 85f9d0f..d553e46 100644
>> --- a/drivers/scsi/ufs/ufshcd.h
>> +++ b/drivers/scsi/ufs/ufshcd.h
>> @@ -419,7 +419,10 @@ struct ufs_saved_pwr_info {
>>   * @suspend_work: worker to suspend devfreq
>>   * @resume_work: worker to resume devfreq
>>   * @min_gear: lowest HS gear to scale down to
>> - * @is_allowed: tracks if scaling is currently allowed or not
>> + * @is_enabled: tracks if scaling is currently enabled or not, 
>> controlled by
>> +		clkscale_enable sysfs node
>> + * @is_allowed: tracks if scaling is currently allowed or not, used 
>> to block
>> +		clock scaling which is not invoked from devfreq governor
>>   * @is_busy_started: tracks if busy period has started or not
>>   * @is_suspended: tracks if devfreq is suspended or not
>>   */
>> @@ -434,6 +437,7 @@ struct ufs_clk_scaling {
>>  	struct work_struct suspend_work;
>>  	struct work_struct resume_work;
>>  	u32 min_gear;
>> +	bool is_enabled;
>>  	bool is_allowed;
>>  	bool is_busy_started;
>>  	bool is_suspended;