[PATCH v3 0/3] Fix UFS and devfreq interaction

[PATCH v3 0/3] Fix UFS and devfreq interaction

[Bjorn Andersson]

With the introduction of f1d981eaecf8 ("PM / devfreq: Use the available min/max
frequency") the UFS host controller driver (UFSHCD) stopped probing for
platforms that supports frequency scaling, e.g. all modern Qualcomm platforms.

The cause of this was UFSHCD's reliance of not registering any frequencies and
then being called by devfreq to switch between the frequencies 0 and UINT_MAX.

The devfreq code implies that the client is able to pass the frequency table,
instead of relying on opp tables, but as concluded after v1 this is not
compliant with devfreq cooling, which will enable and disable opp entries in
order to limit the valid frequencies. So instead the UFSHCD driver is modified
to read the freq-table and register the first clock's two rates as the two
available opp levels.


This follows the first patch which facilitates the implementation of this in a
clean fashion, and removes the kernel panic which previously happened when
devfreq initialization failed.


With this UFS is once again functional on the db820c, and is needed to get UFS
working on SDM845 (both tested).

Added in v3 is the dts patch for Andy to introduce UFS in msm8996 and db820c,
now that it finally works again.

Bjorn Andersson (3):
  scsi: ufs: Extract devfreq registration
  scsi: ufs: Use freq table with devfreq
  arm64: dts: qcom: msm8996: Add ufs related nodes

 arch/arm64/boot/dts/qcom/apq8096-db820c.dtsi |  8 ++
 arch/arm64/boot/dts/qcom/msm8996.dtsi        | 85 ++++++++++++++++++++
 drivers/scsi/ufs/ufshcd.c                    | 76 +++++++++++++----
 3 files changed, 154 insertions(+), 15 deletions(-)

-- 
2.17.0

[PATCH v3 1/3] scsi: ufs: Extract devfreq registration

[Bjorn Andersson]

Failing to register with devfreq leaves hba->devfreq assigned, which
causes the error path to dereference the ERR_PTR(). Rather than bolting
on more conditionals, move the call of devm_devfreq_add_device() into
it's own function and only update hba->devfreq once it's successfully
registered.

The subsequent patch builds upon this to make UFS actually work again,
as it's been broken since f1d981eaecf8 ("PM / devfreq: Use the available
min/max frequency")

Also switch to use DEVFREQ_GOV_SIMPLE_ONDEMAND constant.

Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
---

Changes since v2:
- Use DEVFREQ_GOV_SIMPLE_ONDEMAND, per Chanwoo's recommendation
- Picked up Chanwoo's R-b

Changes since v1:
- None

 drivers/scsi/ufs/ufshcd.c | 31 ++++++++++++++++++++++---------
 1 file changed, 22 insertions(+), 9 deletions(-)

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index 00e79057f870..f04902a066cb 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -1287,6 +1287,26 @@ static struct devfreq_dev_profile ufs_devfreq_profile = {
 	.get_dev_status	= ufshcd_devfreq_get_dev_status,
 };
 
+static int ufshcd_devfreq_init(struct ufs_hba *hba)
+{
+	struct devfreq *devfreq;
+	int ret;
+
+	devfreq = devm_devfreq_add_device(hba->dev,
+			&ufs_devfreq_profile,
+			DEVFREQ_GOV_SIMPLE_ONDEMAND,
+			NULL);
+	if (IS_ERR(devfreq)) {
+		ret = PTR_ERR(devfreq);
+		dev_err(hba->dev, "Unable to register with devfreq %d\n", ret);
+		return ret;
+	}
+
+	hba->devfreq = devfreq;
+
+	return 0;
+}
+
 static void __ufshcd_suspend_clkscaling(struct ufs_hba *hba)
 {
 	unsigned long flags;
@@ -6439,16 +6459,9 @@ static int ufshcd_probe_hba(struct ufs_hba *hba)
 				sizeof(struct ufs_pa_layer_attr));
 			hba->clk_scaling.saved_pwr_info.is_valid = true;
 			if (!hba->devfreq) {
-				hba->devfreq = devm_devfreq_add_device(hba->dev,
-							&ufs_devfreq_profile,
-							"simple_ondemand",
-							NULL);
-				if (IS_ERR(hba->devfreq)) {
-					ret = PTR_ERR(hba->devfreq);
-					dev_err(hba->dev, "Unable to register with devfreq %d\n",
-							ret);
+				ret = ufshcd_devfreq_init(hba);
+				if (ret)
 					goto out;
-				}
 			}
 			hba->clk_scaling.is_allowed = true;
 		}
-- 
2.17.0

[PATCH v3 2/3] scsi: ufs: Use freq table with devfreq

[Bjorn Andersson]

devfreq requires that the client operates on actual frequencies, not
only 0 and UMAX_INT and as such UFS brok with the introduction of
f1d981eaecf8 ("PM / devfreq: Use the available min/max frequency").

This patch registers the frequencies of the first clock with devfreq and
use these to determine if we're trying to step up or down.

Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com> [for devfreq & OPP part]
Reviewed-by: Subhash Jadavani <subhashj@codeaurora.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
---

Changes since v2:
- Picked up R-b from Chanwoo and Subhash

Chances since v1:
- Register min_freq and max_freq as opp levels.
- Unregister opp levels on removal, to make e.g. probe defer working

 drivers/scsi/ufs/ufshcd.c | 47 +++++++++++++++++++++++++++++++++------
 1 file changed, 40 insertions(+), 7 deletions(-)

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index f04902a066cb..3d46a70ed41d 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -1200,16 +1200,13 @@ static int ufshcd_devfreq_target(struct device *dev,
 	struct ufs_hba *hba = dev_get_drvdata(dev);
 	ktime_t start;
 	bool scale_up, sched_clk_scaling_suspend_work = false;
+	struct list_head *clk_list = &hba->clk_list_head;
+	struct ufs_clk_info *clki;
 	unsigned long irq_flags;
 
 	if (!ufshcd_is_clkscaling_supported(hba))
 		return -EINVAL;
 
-	if ((*freq > 0) && (*freq < UINT_MAX)) {
-		dev_err(hba->dev, "%s: invalid freq = %lu\n", __func__, *freq);
-		return -EINVAL;
-	}
-
 	spin_lock_irqsave(hba->host->host_lock, irq_flags);
 	if (ufshcd_eh_in_progress(hba)) {
 		spin_unlock_irqrestore(hba->host->host_lock, irq_flags);
@@ -1219,7 +1216,13 @@ static int ufshcd_devfreq_target(struct device *dev,
 	if (!hba->clk_scaling.active_reqs)
 		sched_clk_scaling_suspend_work = true;
 
-	scale_up = (*freq == UINT_MAX) ? true : false;
+	if (list_empty(clk_list)) {
+		spin_unlock_irqrestore(hba->host->host_lock, irq_flags);
+		goto out;
+	}
+
+	clki = list_first_entry(&hba->clk_list_head, struct ufs_clk_info, list);
+	scale_up = (*freq == clki->max_freq) ? true : false;
 	if (!ufshcd_is_devfreq_scaling_required(hba, scale_up)) {
 		spin_unlock_irqrestore(hba->host->host_lock, irq_flags);
 		ret = 0;
@@ -1289,16 +1292,29 @@ static struct devfreq_dev_profile ufs_devfreq_profile = {
 
 static int ufshcd_devfreq_init(struct ufs_hba *hba)
 {
+	struct list_head *clk_list = &hba->clk_list_head;
+	struct ufs_clk_info *clki;
 	struct devfreq *devfreq;
 	int ret;
 
-	devfreq = devm_devfreq_add_device(hba->dev,
+	/* Skip devfreq if we don't have any clocks in the list */
+	if (list_empty(clk_list))
+		return 0;
+
+	clki = list_first_entry(clk_list, struct ufs_clk_info, list);
+	dev_pm_opp_add(hba->dev, clki->min_freq, 0);
+	dev_pm_opp_add(hba->dev, clki->max_freq, 0);
+
+	devfreq = devfreq_add_device(hba->dev,
 			&ufs_devfreq_profile,
 			DEVFREQ_GOV_SIMPLE_ONDEMAND,
 			NULL);
 	if (IS_ERR(devfreq)) {
 		ret = PTR_ERR(devfreq);
 		dev_err(hba->dev, "Unable to register with devfreq %d\n", ret);
+
+		dev_pm_opp_remove(hba->dev, clki->min_freq);
+		dev_pm_opp_remove(hba->dev, clki->max_freq);
 		return ret;
 	}
 
@@ -1307,6 +1323,22 @@ static int ufshcd_devfreq_init(struct ufs_hba *hba)
 	return 0;
 }
 
+static void ufshcd_devfreq_remove(struct ufs_hba *hba)
+{
+	struct list_head *clk_list = &hba->clk_list_head;
+	struct ufs_clk_info *clki;
+
+	if (!hba->devfreq)
+		return;
+
+	devfreq_remove_device(hba->devfreq);
+	hba->devfreq = NULL;
+
+	clki = list_first_entry(clk_list, struct ufs_clk_info, list);
+	dev_pm_opp_remove(hba->dev, clki->min_freq);
+	dev_pm_opp_remove(hba->dev, clki->max_freq);
+}
+
 static void __ufshcd_suspend_clkscaling(struct ufs_hba *hba)
 {
 	unsigned long flags;
@@ -7005,6 +7037,7 @@ static void ufshcd_hba_exit(struct ufs_hba *hba)
 			if (hba->devfreq)
 				ufshcd_suspend_clkscaling(hba);
 			destroy_workqueue(hba->clk_scaling.workq);
+			ufshcd_devfreq_remove(hba);
 		}
 		ufshcd_setup_clocks(hba, false);
 		ufshcd_setup_hba_vreg(hba, false);
-- 
2.17.0

Re: [PATCH v3 0/3] Fix UFS and devfreq interaction

[Martin K. Petersen]

Bjorn,

> With the introduction of f1d981eaecf8 ("PM / devfreq: Use the
> available min/max frequency") the UFS host controller driver (UFSHCD)
> stopped probing for platforms that supports frequency scaling,
> e.g. all modern Qualcomm platforms.

Applied to 4.18/scsi-queue. Thank you!

-- 
Martin K. Petersen	Oracle Linux Engineering