ufs: Add support for clock scaling using devfreq framework

The clocks for UFS device will be managed by generic DVFS (Dynamic
Voltage and Frequency Scaling) framework within kernel. This devfreq
framework works with different governors to scale the clocks. By default,
UFS devices uses simple_ondemand governor which scales the clocks up if
the load is more than upthreshold and scales down if the load is less than
downthreshold.

Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>
Signed-off-by: Dolev Raviv <draviv@codeaurora.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>

1 files changed, 177 insertions, 1 deletions

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index 6f1ea5192db6..df525e3b2c19 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -38,6 +38,7 @@
  */
 
 #include <linux/async.h>
+#include <linux/devfreq.h>
 
 #include "ufshcd.h"
 #include "unipro.h"
@@ -545,6 +546,8 @@ static void ufshcd_ungate_work(struct work_struct *work)
 		hba->clk_gating.is_suspended = false;
 	}
 unblock_reqs:
+	if (ufshcd_is_clkscaling_enabled(hba))
+		devfreq_resume_device(hba->devfreq);
 	scsi_unblock_requests(hba->host);
 }
 
@@ -561,10 +564,10 @@ int ufshcd_hold(struct ufs_hba *hba, bool async)
 
 	if (!ufshcd_is_clkgating_allowed(hba))
 		goto out;
-start:
 	spin_lock_irqsave(hba->host->host_lock, flags);
 	hba->clk_gating.active_reqs++;
 
+start:
 	switch (hba->clk_gating.state) {
 	case CLKS_ON:
 		break;
@@ -596,6 +599,7 @@ start:
 		spin_unlock_irqrestore(hba->host->host_lock, flags);
 		flush_work(&hba->clk_gating.ungate_work);
 		/* Make sure state is CLKS_ON before returning */
+		spin_lock_irqsave(hba->host->host_lock, flags);
 		goto start;
 	default:
 		dev_err(hba->dev, "%s: clk gating is in invalid state %d\n",
@@ -636,6 +640,11 @@ static void ufshcd_gate_work(struct work_struct *work)
 		ufshcd_set_link_hibern8(hba);
 	}
 
+	if (ufshcd_is_clkscaling_enabled(hba)) {
+		devfreq_suspend_device(hba->devfreq);
+		hba->clk_scaling.window_start_t = 0;
+	}
+
 	if (!ufshcd_is_link_active(hba))
 		ufshcd_setup_clocks(hba, false);
 	else
@@ -737,6 +746,32 @@ static void ufshcd_exit_clk_gating(struct ufs_hba *hba)
 	device_remove_file(hba->dev, &hba->clk_gating.delay_attr);
 }
 
+/* Must be called with host lock acquired */
+static void ufshcd_clk_scaling_start_busy(struct ufs_hba *hba)
+{
+	if (!ufshcd_is_clkscaling_enabled(hba))
+		return;
+
+	if (!hba->clk_scaling.is_busy_started) {
+		hba->clk_scaling.busy_start_t = ktime_get();
+		hba->clk_scaling.is_busy_started = true;
+	}
+}
+
+static void ufshcd_clk_scaling_update_busy(struct ufs_hba *hba)
+{
+	struct ufs_clk_scaling *scaling = &hba->clk_scaling;
+
+	if (!ufshcd_is_clkscaling_enabled(hba))
+		return;
+
+	if (!hba->outstanding_reqs && scaling->is_busy_started) {
+		scaling->tot_busy_t += ktime_to_us(ktime_sub(ktime_get(),
+					scaling->busy_start_t));
+		scaling->busy_start_t = ktime_set(0, 0);
+		scaling->is_busy_started = false;
+	}
+}
 /**
  * ufshcd_send_command - Send SCSI or device management commands
  * @hba: per adapter instance
@@ -745,6 +780,7 @@ static void ufshcd_exit_clk_gating(struct ufs_hba *hba)
 static inline
 void ufshcd_send_command(struct ufs_hba *hba, unsigned int task_tag)
 {
+	ufshcd_clk_scaling_start_busy(hba);
 	__set_bit(task_tag, &hba->outstanding_reqs);
 	ufshcd_writel(hba, 1 << task_tag, REG_UTP_TRANSFER_REQ_DOOR_BELL);
 }
@@ -3027,6 +3063,8 @@ static void ufshcd_transfer_req_compl(struct ufs_hba *hba)
 	/* clear corresponding bits of completed commands */
 	hba->outstanding_reqs ^= completed_reqs;
 
+	ufshcd_clk_scaling_update_busy(hba);
+
 	/* we might have free'd some tags above */
 	wake_up(&hba->dev_cmd.tag_wq);
 }
@@ -4151,6 +4189,10 @@ static int ufshcd_probe_hba(struct ufs_hba *hba)
 	if (!hba->is_init_prefetch)
 		hba->is_init_prefetch = true;
 
+	/* Resume devfreq after UFS device is detected */
+	if (ufshcd_is_clkscaling_enabled(hba))
+		devfreq_resume_device(hba->devfreq);
+
 out:
 	/*
 	 * If we failed to initialize the device or the device is not
@@ -4472,6 +4514,7 @@ static int ufshcd_init_clocks(struct ufs_hba *hba)
 					clki->max_freq, ret);
 				goto out;
 			}
+			clki->curr_freq = clki->max_freq;
 		}
 		dev_dbg(dev, "%s: clk: %s, rate: %lu\n", __func__,
 				clki->name, clk_get_rate(clki->clk));
@@ -4868,6 +4911,15 @@ static int ufshcd_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
 
 disable_clks:
 	/*
+	 * The clock scaling needs access to controller registers. Hence, Wait
+	 * for pending clock scaling work to be done before clocks are
+	 * turned off.
+	 */
+	if (ufshcd_is_clkscaling_enabled(hba)) {
+		devfreq_suspend_device(hba->devfreq);
+		hba->clk_scaling.window_start_t = 0;
+	}
+	/*
 	 * Call vendor specific suspend callback. As these callbacks may access
 	 * vendor specific host controller register space call them before the
 	 * host clocks are ON.
@@ -4989,6 +5041,9 @@ static int ufshcd_resume(struct ufs_hba *hba, enum ufs_pm_op pm_op)
 	ufshcd_disable_auto_bkops(hba);
 	hba->clk_gating.is_suspended = false;
 
+	if (ufshcd_is_clkscaling_enabled(hba))
+		devfreq_resume_device(hba->devfreq);
+
 	/* Schedule clock gating in case of no access to UFS device yet */
 	ufshcd_release(hba);
 	goto out;
@@ -5172,6 +5227,8 @@ void ufshcd_remove(struct ufs_hba *hba)
 	scsi_host_put(hba->host);
 
 	ufshcd_exit_clk_gating(hba);
+	if (ufshcd_is_clkscaling_enabled(hba))
+		devfreq_remove_device(hba->devfreq);
 	ufshcd_hba_exit(hba);
 }
 EXPORT_SYMBOL_GPL(ufshcd_remove);
@@ -5228,6 +5285,112 @@ out_error:
 }
 EXPORT_SYMBOL(ufshcd_alloc_host);
 
+static int ufshcd_scale_clks(struct ufs_hba *hba, bool scale_up)
+{
+	int ret = 0;
+	struct ufs_clk_info *clki;
+	struct list_head *head = &hba->clk_list_head;
+
+	if (!head || list_empty(head))
+		goto out;
+
+	list_for_each_entry(clki, head, list) {
+		if (!IS_ERR_OR_NULL(clki->clk)) {
+			if (scale_up && clki->max_freq) {
+				if (clki->curr_freq == clki->max_freq)
+					continue;
+				ret = clk_set_rate(clki->clk, clki->max_freq);
+				if (ret) {
+					dev_err(hba->dev, "%s: %s clk set rate(%dHz) failed, %d\n",
+						__func__, clki->name,
+						clki->max_freq, ret);
+					break;
+				}
+				clki->curr_freq = clki->max_freq;
+
+			} else if (!scale_up && clki->min_freq) {
+				if (clki->curr_freq == clki->min_freq)
+					continue;
+				ret = clk_set_rate(clki->clk, clki->min_freq);
+				if (ret) {
+					dev_err(hba->dev, "%s: %s clk set rate(%dHz) failed, %d\n",
+						__func__, clki->name,
+						clki->min_freq, ret);
+					break;
+				}
+				clki->curr_freq = clki->min_freq;
+			}
+		}
+		dev_dbg(hba->dev, "%s: clk: %s, rate: %lu\n", __func__,
+				clki->name, clk_get_rate(clki->clk));
+	}
+	if (hba->vops->clk_scale_notify)
+		hba->vops->clk_scale_notify(hba);
+out:
+	return ret;
+}
+
+static int ufshcd_devfreq_target(struct device *dev,
+				unsigned long *freq, u32 flags)
+{
+	int err = 0;
+	struct ufs_hba *hba = dev_get_drvdata(dev);
+
+	if (!ufshcd_is_clkscaling_enabled(hba))
+		return -EINVAL;
+
+	if (*freq == UINT_MAX)
+		err = ufshcd_scale_clks(hba, true);
+	else if (*freq == 0)
+		err = ufshcd_scale_clks(hba, false);
+
+	return err;
+}
+
+static int ufshcd_devfreq_get_dev_status(struct device *dev,
+		struct devfreq_dev_status *stat)
+{
+	struct ufs_hba *hba = dev_get_drvdata(dev);
+	struct ufs_clk_scaling *scaling = &hba->clk_scaling;
+	unsigned long flags;
+
+	if (!ufshcd_is_clkscaling_enabled(hba))
+		return -EINVAL;
+
+	memset(stat, 0, sizeof(*stat));
+
+	spin_lock_irqsave(hba->host->host_lock, flags);
+	if (!scaling->window_start_t)
+		goto start_window;
+
+	if (scaling->is_busy_started)
+		scaling->tot_busy_t += ktime_to_us(ktime_sub(ktime_get(),
+					scaling->busy_start_t));
+
+	stat->total_time = jiffies_to_usecs((long)jiffies -
+				(long)scaling->window_start_t);
+	stat->busy_time = scaling->tot_busy_t;
+start_window:
+	scaling->window_start_t = jiffies;
+	scaling->tot_busy_t = 0;
+
+	if (hba->outstanding_reqs) {
+		scaling->busy_start_t = ktime_get();
+		scaling->is_busy_started = true;
+	} else {
+		scaling->busy_start_t = ktime_set(0, 0);
+		scaling->is_busy_started = false;
+	}
+	spin_unlock_irqrestore(hba->host->host_lock, flags);
+	return 0;
+}
+
+static struct devfreq_dev_profile ufs_devfreq_profile = {
+	.polling_ms	= 100,
+	.target		= ufshcd_devfreq_target,
+	.get_dev_status	= ufshcd_devfreq_get_dev_status,
+};
+
 /**
  * ufshcd_init - Driver initialization routine
  * @hba: per-adapter instance
@@ -5337,6 +5500,19 @@ int ufshcd_init(struct ufs_hba *hba, void __iomem *mmio_base, unsigned int irq)
 		goto out_remove_scsi_host;
 	}
 
+	if (ufshcd_is_clkscaling_enabled(hba)) {
+		hba->devfreq = devfreq_add_device(dev, &ufs_devfreq_profile,
+						   "simple_ondemand", NULL);
+		if (IS_ERR(hba->devfreq)) {
+			dev_err(hba->dev, "Unable to register with devfreq %ld\n",
+					PTR_ERR(hba->devfreq));
+			goto out_remove_scsi_host;
+		}
+		/* Suspend devfreq until the UFS device is detected */
+		devfreq_suspend_device(hba->devfreq);
+		hba->clk_scaling.window_start_t = 0;
+	}
+
 	/* Hold auto suspend until async scan completes */
 	pm_runtime_get_sync(dev);