scsi: ufs: core: Add CPU latency QoS support for UFS driver

Register UFS driver to CPU latency PM QoS framework to improve UFS device
random I/O performance.

PM QoS initialization will insert new QoS request into the CPU latency QoS
list with the maximum latency PM_QOS_DEFAULT_VALUE value.

The UFS driver will vote for performance mode on scale up and power save
mode for scale down.

If clock scaling feature is not enabled then voting will be based on clock
on or off condition. Also provide a sysfs interface to enable/disable PM
QoS feature.

tiotest benchmark tool I/O performance results on sm8550 platform:

1. Without PM QoS support
	Type (Speed in)    | Average of 18 iterations
	Random Write(IPOS) | 41065.13
	Random Read(IPOS)  | 37101.3

2. With PM QoS support
	Type (Speed in)    | Average of 18 iterations
	Random Write(IPOS) | 46784.9
	Random Read(IPOS)  | 42943.4

(Improvement with PM QoS = ~15%).

Reviewed-by: Peter Wang <peter.wang@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Co-developed-by: Nitin Rawat <quic_nitirawa@quicinc.com>
Signed-off-by: Nitin Rawat <quic_nitirawa@quicinc.com>
Co-developed-by: Naveen Kumar Goud Arepalli <quic_narepall@quicinc.com>
Signed-off-by: Naveen Kumar Goud Arepalli <quic_narepall@quicinc.com>
Signed-off-by: Maramaina Naresh <quic_mnaresh@quicinc.com>
Link: https://lore.kernel.org/r/20231219123706.6463-2-quic_mnaresh@quicinc.com
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

1 files changed, 49 insertions, 0 deletions

diff --git a/drivers/ufs/core/ufs-sysfs.c b/drivers/ufs/core/ufs-sysfs.c
index e6d12289e017..3d049967f6bc 100644
--- a/drivers/ufs/core/ufs-sysfs.c
+++ b/drivers/ufs/core/ufs-sysfs.c
@@ -405,6 +405,53 @@ static ssize_t wb_flush_threshold_store(struct device *dev,
 	return count;
 }
 
+/**
+ * pm_qos_enable_show - sysfs handler to show pm qos enable value
+ * @dev: device associated with the UFS controller
+ * @attr: sysfs attribute handle
+ * @buf: buffer for sysfs file
+ *
+ * Print 1 if PM QoS feature is enabled, 0 if disabled.
+ *
+ * Returns number of characters written to @buf.
+ */
+static ssize_t pm_qos_enable_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct ufs_hba *hba = dev_get_drvdata(dev);
+
+	return sysfs_emit(buf, "%d\n", hba->pm_qos_enabled);
+}
+
+/**
+ * pm_qos_enable_store - sysfs handler to store value
+ * @dev: device associated with the UFS controller
+ * @attr: sysfs attribute handle
+ * @buf: buffer for sysfs file
+ * @count: stores buffer characters count
+ *
+ * Input 0 to disable PM QoS and 1 value to enable.
+ * Default state: 1
+ *
+ * Return: number of characters written to @buf on success, < 0 upon failure.
+ */
+static ssize_t pm_qos_enable_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t count)
+{
+	struct ufs_hba *hba = dev_get_drvdata(dev);
+	bool value;
+
+	if (kstrtobool(buf, &value))
+		return -EINVAL;
+
+	if (value)
+		ufshcd_pm_qos_init(hba);
+	else
+		ufshcd_pm_qos_exit(hba);
+
+	return count;
+}
+
 static DEVICE_ATTR_RW(rpm_lvl);
 static DEVICE_ATTR_RO(rpm_target_dev_state);
 static DEVICE_ATTR_RO(rpm_target_link_state);
@@ -416,6 +463,7 @@ static DEVICE_ATTR_RW(wb_on);
 static DEVICE_ATTR_RW(enable_wb_buf_flush);
 static DEVICE_ATTR_RW(wb_flush_threshold);
 static DEVICE_ATTR_RW(rtc_update_ms);
+static DEVICE_ATTR_RW(pm_qos_enable);
 
 static struct attribute *ufs_sysfs_ufshcd_attrs[] = {
 	&dev_attr_rpm_lvl.attr,
@@ -429,6 +477,7 @@ static struct attribute *ufs_sysfs_ufshcd_attrs[] = {
 	&dev_attr_enable_wb_buf_flush.attr,
 	&dev_attr_wb_flush_threshold.attr,
 	&dev_attr_rtc_update_ms.attr,
+	&dev_attr_pm_qos_enable.attr,
 	NULL
 };