scsi: ufs: core: Add support to notify userspace of UniPro QoS events

The UniPro stack manages to repair many potential Link problems without the
need to notify the Application Layer. Repair mechanisms of the stack
include L2 re-transmission and successful handling of PA_INIT.req.
Nevertheless, any successful repair sequence requires Link bandwidth that
is no longer vailable for the Application. Therefore, it may be useful for
an Application to understand how often such repair attempts are made.

The DME implements Quality of Service monitoring using a simple counting
scheme, counting error events and comparing them against the number of
correctly received or transmitted bytes. When the error counter exceeds a
programmed threshold before the byte counter overflows, a DME_QoS.ind is
issued to the Application and both counters are reset. When the byte
counter overflows before the error counter has reached the programmed
threshold, both counters are reset without triggering a DME_QoS.ind.

The DME provides Link quality monitoring for the following purposes:

1. Detection of re-occurring repaired fatal error conditions on the Link
   (PA_INIT loop). This kind of detection is useful if capabilities
   exchanged between local and peer permit a potential operation at a
   higher M-PHY Gear, but the physical interconnect between local and peer
   Device does not, or, after Line quality degradation, no longer satisfies
   channel characteristics.

2. Detection of degraded inbound or outbound Link quality, to allow an
   Application to issue an ADAPT sequence for a Link running in HS-G4 or
   higher HS Gears. This kind of detection is used to monitor a slowly
   degrading Link quality, e.g., one being affected by temperature and
   voltage variations, against the expected M-PHY bit error rate.

Userspace can configure and enable UniPro QoS via UniPro QoS Attributes
(via UFS BSG) and get notified by dme_qos_notification without polling
UniPro QoS Status attribute. The dme_qos_notification attribute is a
bitfield with the following bit assignments:

   Bit	Description
   ===	======================================
   0	DME QoS Monitor has been reset by host
   1	QoS from TX is detected
   2	QoS from RX is detected
   3	QoS from PA_INIT is detected

Signed-off-by: Can Guo <can.guo@oss.qualcomm.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Peter Wang <peter.wang@mediatek.com>
Link: https://patch.msgid.link/20260305110856.959211-2-can.guo@oss.qualcomm.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

2 files changed, 51 insertions, 3 deletions

diff --git a/drivers/ufs/core/ufs-sysfs.c b/drivers/ufs/core/ufs-sysfs.c
index 384d958615d7..99af3c73f1af 100644
--- a/drivers/ufs/core/ufs-sysfs.c
+++ b/drivers/ufs/core/ufs-sysfs.c
@@ -605,6 +605,34 @@ static ssize_t device_lvl_exception_id_show(struct device *dev,
 	return sysfs_emit(buf, "%llu\n", exception_id);
 }
 
+static ssize_t dme_qos_notification_show(struct device *dev,
+					 struct device_attribute *attr,
+					 char *buf)
+{
+	struct ufs_hba *hba = dev_get_drvdata(dev);
+
+	return sysfs_emit(buf, "0x%x\n", atomic_read(&hba->dme_qos_notification));
+}
+
+static ssize_t dme_qos_notification_store(struct device *dev,
+					  struct device_attribute *attr,
+					  const char *buf, size_t count)
+{
+	struct ufs_hba *hba = dev_get_drvdata(dev);
+	unsigned int value;
+
+	if (kstrtouint(buf, 0, &value))
+		return -EINVAL;
+
+	/* the only supported usecase is to reset the dme_qos_notification */
+	if (value)
+		return -EINVAL;
+
+	atomic_set(&hba->dme_qos_notification, 0);
+
+	return count;
+}
+
 static DEVICE_ATTR_RW(rpm_lvl);
 static DEVICE_ATTR_RO(rpm_target_dev_state);
 static DEVICE_ATTR_RO(rpm_target_link_state);
@@ -621,6 +649,7 @@ static DEVICE_ATTR_RW(pm_qos_enable);
 static DEVICE_ATTR_RO(critical_health);
 static DEVICE_ATTR_RW(device_lvl_exception_count);
 static DEVICE_ATTR_RO(device_lvl_exception_id);
+static DEVICE_ATTR_RW(dme_qos_notification);
 
 static struct attribute *ufs_sysfs_ufshcd_attrs[] = {
 	&dev_attr_rpm_lvl.attr,
@@ -639,6 +668,7 @@ static struct attribute *ufs_sysfs_ufshcd_attrs[] = {
 	&dev_attr_critical_health.attr,
 	&dev_attr_device_lvl_exception_count.attr,
 	&dev_attr_device_lvl_exception_id.attr,
+	&dev_attr_dme_qos_notification.attr,
 	NULL
 };
 
diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
index 017d05ef94e2..8658e6dc8634 100644
--- a/drivers/ufs/core/ufshcd.c
+++ b/drivers/ufs/core/ufshcd.c
@@ -6966,10 +6966,19 @@ static irqreturn_t ufshcd_update_uic_error(struct ufs_hba *hba)
 	}
 
 	reg = ufshcd_readl(hba, REG_UIC_ERROR_CODE_DME);
-	if ((reg & UIC_DME_ERROR) &&
-	    (reg & UIC_DME_ERROR_CODE_MASK)) {
+	if (reg & UIC_DME_ERROR) {
 		ufshcd_update_evt_hist(hba, UFS_EVT_DME_ERR, reg);
-		hba->uic_error |= UFSHCD_UIC_DME_ERROR;
+
+		if (reg & UIC_DME_ERROR_CODE_MASK)
+			hba->uic_error |= UFSHCD_UIC_DME_ERROR;
+
+		if (reg & UIC_DME_QOS_MASK) {
+			atomic_set(&hba->dme_qos_notification,
+				   reg & UIC_DME_QOS_MASK);
+			if (hba->dme_qos_sysfs_handle)
+				sysfs_notify_dirent(hba->dme_qos_sysfs_handle);
+		}
+
 		retval |= IRQ_HANDLED;
 	}
 
@@ -9101,6 +9110,12 @@ static int ufshcd_post_device_init(struct ufs_hba *hba)
 
 	/* UFS device is also active now */
 	ufshcd_set_ufs_dev_active(hba);
+
+	/* Indicate that DME QoS Monitor has been reset */
+	atomic_set(&hba->dme_qos_notification, 0x1);
+	if (hba->dme_qos_sysfs_handle)
+		sysfs_notify_dirent(hba->dme_qos_sysfs_handle);
+
 	ufshcd_force_reset_auto_bkops(hba);
 
 	ufshcd_set_timestamp_attr(hba);
@@ -9733,6 +9748,7 @@ static void ufshcd_hba_exit(struct ufs_hba *hba)
 		hba->is_powered = false;
 		ufs_put_device_desc(hba);
 	}
+	sysfs_put(hba->dme_qos_sysfs_handle);
 }
 
 static int ufshcd_execute_start_stop(struct scsi_device *sdev,
@@ -11052,6 +11068,8 @@ initialized:
 		goto out_disable;
 
 	ufs_sysfs_add_nodes(hba->dev);
+	hba->dme_qos_sysfs_handle = sysfs_get_dirent(hba->dev->kobj.sd,
+						     "dme_qos_notification");
 	async_schedule(ufshcd_async_scan, hba);
 
 	device_enable_async_suspend(dev);