scsi: ufs: Add batched WB buffer flush

Currently, WriteBooster (WB) buffer is always flushed during hibern8. However,
this is inefficient because data in the WB buffer can be invalid due to
spatial locality of IO workload.
If the WB buffer flush is flushed in a batched manner, the amount of data
migration and power consumption can be reduced because the overwritten data
of the WB buffer may be invalid due to spatial locality.

This patch supports batched flush of WB buffer. When batched flush is enabled,
fWriteBoosterBufferFlushDuringHibernate is set only when
b_rpm_dev_flush_capable is true during runtime suspend. When the device is
resumed, fWriteBoosterBufferFlushDuringHibernate is cleared to stop flush
during hibern8.

Co-developed-by: Keoseong Park <keosung.park@samsung.com>
Signed-off-by: Keoseong Park <keosung.park@samsung.com>
Signed-off-by: Daejun Park <daejun7.park@samsung.com>

Documentation/ABI/testing/sysfs-driver-ufs

@@ -1172,3 +1172,12 @@ Description:	This node is used to set or display whether UFS WriteBooster is
 		(if the platform supports UFSHCD_CAP_CLK_SCALING). For a
 		platform that doesn't support UFSHCD_CAP_CLK_SCALING, we can
 		disable/enable WriteBooster through this sysfs node.
+
+What:		/sys/bus/platform/drivers/ufshcd/*/wb_batched_flush
+Date:		April 2021
+Contact:	Daejun Park <daejun7.park@samsung.com>
+Description:	This entry shows whether batch flushing of UFS WriteBooster
+		buffers is enabled. Writing 1 to this entry allows the device to flush
+		the WriteBooster buffer only when it needs to perform a buffer flush
+		during runtime suspend. Writing 0 to this entry allows the device to
+		flush the WriteBooster buffer during link hibernation.

drivers/scsi/ufs/ufs-sysfs.c

@@ -253,6 +253,54 @@ static ssize_t wb_on_store(struct device *dev, struct device_attribute *attr,
 	return res < 0 ? res : count;
 }
 
+
+static ssize_t wb_batched_flush_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->vps->wb_batched_flush);
+}
+
+static ssize_t wb_batched_flush_store(struct device *dev,
+				      struct device_attribute *attr,
+				      const char *buf, size_t count)
+{
+	struct ufs_hba *hba = dev_get_drvdata(dev);
+	unsigned int wb_batched_flush;
+	ssize_t res;
+
+	if (!ufshcd_is_wb_allowed(hba)) {
+		dev_warn(dev, "To control WB through wb_batched_flush is not allowed!\n");
+		return -EOPNOTSUPP;
+	}
+
+	if (kstrtouint(buf, 0, &wb_batched_flush))
+		return -EINVAL;
+
+	if (wb_batched_flush != 0 && wb_batched_flush != 1)
+		return -EINVAL;
+
+	down(&hba->host_sem);
+	if (!ufshcd_is_user_access_allowed(hba)) {
+		res = -EBUSY;
+		goto out;
+	}
+
+	if (wb_batched_flush == hba->vps->wb_batched_flush)
+		goto out;
+
+	pm_runtime_get_sync(hba->dev);
+	res = ufshcd_wb_toggle_flush_during_h8(hba, !wb_batched_flush);
+	pm_runtime_put_sync(hba->dev);
+	if (!res)
+		hba->vps->wb_batched_flush = wb_batched_flush;
+
+out:
+	up(&hba->host_sem);
+	return res < 0 ? res : count;
+}
+
 static DEVICE_ATTR_RW(rpm_lvl);
 static DEVICE_ATTR_RO(rpm_target_dev_state);
 static DEVICE_ATTR_RO(rpm_target_link_state);
@@ -261,6 +309,7 @@ static DEVICE_ATTR_RO(spm_target_dev_state);
 static DEVICE_ATTR_RO(spm_target_link_state);
 static DEVICE_ATTR_RW(auto_hibern8);
 static DEVICE_ATTR_RW(wb_on);
+static DEVICE_ATTR_RW(wb_batched_flush);
 
 static struct attribute *ufs_sysfs_ufshcd_attrs[] = {
 	&dev_attr_rpm_lvl.attr,
@@ -271,6 +320,7 @@ static struct attribute *ufs_sysfs_ufshcd_attrs[] = {
 	&dev_attr_spm_target_link_state.attr,
 	&dev_attr_auto_hibern8.attr,
 	&dev_attr_wb_on.attr,
+	&dev_attr_wb_batched_flush.attr,
 	NULL
 };
 

drivers/scsi/ufs/ufshcd.c

@@ -244,7 +244,6 @@ static int ufshcd_setup_vreg(struct ufs_hba *hba, bool on);
 static inline int ufshcd_config_vreg_hpm(struct ufs_hba *hba,
 					 struct ufs_vreg *vreg);
 static int ufshcd_try_to_abort_task(struct ufs_hba *hba, int tag);
-static void ufshcd_wb_toggle_flush_during_h8(struct ufs_hba *hba, bool set);
 static inline void ufshcd_wb_toggle_flush(struct ufs_hba *hba, bool enable);
 static void ufshcd_hba_vreg_set_lpm(struct ufs_hba *hba);
 static void ufshcd_hba_vreg_set_hpm(struct ufs_hba *hba);
@@ -277,7 +276,8 @@ static inline void ufshcd_wb_config(struct ufs_hba *hba)
 
 	ufshcd_wb_toggle(hba, true);
 
-	ufshcd_wb_toggle_flush_during_h8(hba, true);
+	ufshcd_wb_toggle_flush_during_h8(hba, !hba->vps->wb_batched_flush);
+
 	if (!(hba->quirks & UFSHCI_QUIRK_SKIP_MANUAL_WB_FLUSH_CTRL))
 		ufshcd_wb_toggle_flush(hba, true);
 }
@@ -5472,7 +5472,7 @@ int ufshcd_wb_toggle(struct ufs_hba *hba, bool enable)
 	return ret;
 }
 
-static void ufshcd_wb_toggle_flush_during_h8(struct ufs_hba *hba, bool set)
+int ufshcd_wb_toggle_flush_during_h8(struct ufs_hba *hba, bool set)
 {
 	int ret;
 
@@ -5481,10 +5481,12 @@ static void ufshcd_wb_toggle_flush_during_h8(struct ufs_hba *hba, bool set)
 	if (ret) {
 		dev_err(hba->dev, "%s: WB-Buf Flush during H8 %s failed: %d\n",
 			__func__, set ? "enable" : "disable", ret);
-		return;
+		return ret;
 	}
 	dev_dbg(hba->dev, "%s WB-Buf Flush during H8 %s\n",
 			__func__, set ? "enabled" : "disabled");
+
+	return ret;
 }
 
 static inline void ufshcd_wb_toggle_flush(struct ufs_hba *hba, bool enable)
@@ -8745,6 +8747,8 @@ static int ufshcd_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
 			ret = ufshcd_set_dev_pwr_mode(hba, req_dev_pwr_mode);
 			if (ret)
 				goto enable_gating;
+		} else if (hba->vps->wb_batched_flush) {
+			ufshcd_wb_toggle_flush_during_h8(hba, true);
 		}
 	}
 
@@ -8925,6 +8929,8 @@ static int ufshcd_resume(struct ufs_hba *hba, enum ufs_pm_op pm_op)
 	ufshcd_auto_hibern8_enable(hba);
 
 	if (hba->dev_info.b_rpm_dev_flush_capable) {
+		if (hba->vps->wb_batched_flush)
+			ufshcd_wb_toggle_flush_during_h8(hba, false);
 		hba->dev_info.b_rpm_dev_flush_capable = false;
 		cancel_delayed_work(&hba->rpm_dev_flush_recheck_work);
 	}

drivers/scsi/ufs/ufshcd.h

@@ -643,6 +643,7 @@ struct ufs_hba_variant_params {
 	struct devfreq_simple_ondemand_data ondemand_data;
 	u16 hba_enable_delay_us;
 	u32 wb_flush_threshold;
+	bool wb_batched_flush;
 };
 
 /**
@@ -1105,6 +1106,7 @@ int ufshcd_exec_raw_upiu_cmd(struct ufs_hba *hba,
 			     enum query_opcode desc_op);
 
 int ufshcd_wb_toggle(struct ufs_hba *hba, bool enable);
+int ufshcd_wb_toggle_flush_during_h8(struct ufs_hba *hba, bool set);
 
 /* Wrapper functions for safely calling variant operations */
 static inline const char *ufshcd_get_var_name(struct ufs_hba *hba)