scsi: ufs: Add support for Auto-Hibernate Idle Timer

UFS host controllers may support an autonomous power management feature
called the Auto-Hibernate Idle Timer. The timer is set to the number of
microseconds of idle time before the UFS host controller will autonomously
put the link into Hibernate state. That will save power at the expense of
increased latency. Any access to the host controller interface registers
will automatically put the link out of Hibernate state. So once configured,
the feature is transparent to the driver.

Expose the Auto-Hibernate Idle Timer value via SysFS to allow users to
choose between power efficiency or lower latency. Set a default value of
150 ms.

Signed-off-by: Adrian Hunter <[e-mail]>
Acked-by: Stanislav Nijnikov <[e-mail]>
Signed-off-by: Martin K. Petersen <[e-mail]>

Documentation/ABI/testing/sysfs-driver-ufs

···
+What:		/sys/bus/*/drivers/ufshcd/*/auto_hibern8
+Date:		March 2018
+Contact:	[e-mail]
+Description:
+		This file contains the auto-hibernate idle timer setting of a
+		UFS host controller. A value of '0' means auto-hibernate is not
+		enabled. Otherwise the value is the number of microseconds of
+		idle time before the UFS host controller will autonomously put
+		the link into hibernate state. That will save power at the
+		expense of increased latency. Note that the hardware supports
+		10-bit values with a power-of-ten multiplier which allows a
+		maximum value of 102300000. Refer to the UFS Host Controller
+		Interface specification for more details.
+
 What:		/sys/bus/platform/drivers/ufshcd/*/device_descriptor/device_type
 Date:		February 2018
 Contact:	Stanislav Nijnikov <[e-mail]>

drivers/scsi/ufs/ufs-sysfs.c

···
 
 #include <linux/err.h>
 #include <linux/string.h>
+#include <linux/bitfield.h>
 #include <asm/unaligned.h>
 
 #include "ufs.h"
···
 				ufs_pm_lvl_states[hba->spm_lvl].link_state));
 }
 
+static void ufshcd_auto_hibern8_update(struct ufs_hba *hba, u32 ahit)
+{
+	unsigned long flags;
+
+	if (!(hba->capabilities & MASK_AUTO_HIBERN8_SUPPORT))
+		return;
+
+	spin_lock_irqsave(hba->host->host_lock, flags);
+	if (hba->ahit == ahit)
+		goto out_unlock;
+	hba->ahit = ahit;
+	if (!pm_runtime_suspended(hba->dev))
+		ufshcd_writel(hba, hba->ahit, REG_AUTO_HIBERNATE_IDLE_TIMER);
+out_unlock:
+	spin_unlock_irqrestore(hba->host->host_lock, flags);
+}
+
+/* Convert Auto-Hibernate Idle Timer register value to microseconds */
+static int ufshcd_ahit_to_us(u32 ahit)
+{
+	int timer = FIELD_GET(UFSHCI_AHIBERN8_TIMER_MASK, ahit);
+	int scale = FIELD_GET(UFSHCI_AHIBERN8_SCALE_MASK, ahit);
+
+	for (; scale > 0; --scale)
+		timer *= UFSHCI_AHIBERN8_SCALE_FACTOR;
+
+	return timer;
+}
+
+/* Convert microseconds to Auto-Hibernate Idle Timer register value */
+static u32 ufshcd_us_to_ahit(unsigned int timer)
+{
+	unsigned int scale;
+
+	for (scale = 0; timer > UFSHCI_AHIBERN8_TIMER_MASK; ++scale)
+		timer /= UFSHCI_AHIBERN8_SCALE_FACTOR;
+
+	return FIELD_PREP(UFSHCI_AHIBERN8_TIMER_MASK, timer) |
+	       FIELD_PREP(UFSHCI_AHIBERN8_SCALE_MASK, scale);
+}
+
+static ssize_t auto_hibern8_show(struct device *dev,
+				 struct device_attribute *attr, char *buf)
+{
+	struct ufs_hba *hba = dev_get_drvdata(dev);
+
+	if (!(hba->capabilities & MASK_AUTO_HIBERN8_SUPPORT))
+		return -EOPNOTSUPP;
+
+	return snprintf(buf, PAGE_SIZE, "%d\n", ufshcd_ahit_to_us(hba->ahit));
+}
+
+static ssize_t auto_hibern8_store(struct device *dev,
+				  struct device_attribute *attr,
+				  const char *buf, size_t count)
+{
+	struct ufs_hba *hba = dev_get_drvdata(dev);
+	unsigned int timer;
+
+	if (!(hba->capabilities & MASK_AUTO_HIBERN8_SUPPORT))
+		return -EOPNOTSUPP;
+
+	if (kstrtouint(buf, 0, &timer))
+		return -EINVAL;
+
+	if (timer > UFSHCI_AHIBERN8_MAX)
+		return -EINVAL;
+
+	ufshcd_auto_hibern8_update(hba, ufshcd_us_to_ahit(timer));
+
+	return count;
+}
+
 static DEVICE_ATTR_RW(rpm_lvl);
 static DEVICE_ATTR_RO(rpm_target_dev_state);
 static DEVICE_ATTR_RO(rpm_target_link_state);
 static DEVICE_ATTR_RW(spm_lvl);
 static DEVICE_ATTR_RO(spm_target_dev_state);
 static DEVICE_ATTR_RO(spm_target_link_state);
+static DEVICE_ATTR_RW(auto_hibern8);
 
 static struct attribute *ufs_sysfs_ufshcd_attrs[] = {
 	&dev_attr_rpm_lvl.attr,
···
 	&dev_attr_spm_lvl.attr,
 	&dev_attr_spm_target_dev_state.attr,
 	&dev_attr_spm_target_link_state.attr,
+	&dev_attr_auto_hibern8.attr,
 	NULL
 };
 

drivers/scsi/ufs/ufshcd.c

···
 #include <linux/devfreq.h>
 #include <linux/nls.h>
 #include <linux/of.h>
+#include <linux/bitfield.h>
 #include "ufshcd.h"
 #include "ufs_quirks.h"
 #include "unipro.h"
···
 	return ret;
 }
 
+static void ufshcd_auto_hibern8_enable(struct ufs_hba *hba)
+{
+	unsigned long flags;
+
+	if (!(hba->capabilities & MASK_AUTO_HIBERN8_SUPPORT) || !hba->ahit)
+		return;
+
+	spin_lock_irqsave(hba->host->host_lock, flags);
+	ufshcd_writel(hba, hba->ahit, REG_AUTO_HIBERNATE_IDLE_TIMER);
+	spin_unlock_irqrestore(hba->host->host_lock, flags);
+}
+
  /**
  * ufshcd_init_pwr_info - setting the POR (power on reset)
  * values in hba power info
···
 	/* UniPro link is active now */
 	ufshcd_set_link_active(hba);
 
+	/* Enable Auto-Hibernate if configured */
+	ufshcd_auto_hibern8_enable(hba);
+
 	ret = ufshcd_verify_dev_init(hba);
 	if (ret)
 		goto out;
···
 
 	/* Schedule clock gating in case of no access to UFS device yet */
 	ufshcd_release(hba);
+
+	/* Enable Auto-Hibernate if configured */
+	ufshcd_auto_hibern8_enable(hba);
+
 	goto out;
 
 set_old_link_state:
···
 	hba->spm_lvl = ufs_get_desired_pm_lvl_for_dev_link_state(
 						UFS_SLEEP_PWR_MODE,
 						UIC_LINK_HIBERN8_STATE);
+
+	/* Set the default auto-hiberate idle timer value to 150 ms */
+	if (hba->capabilities & MASK_AUTO_HIBERN8_SUPPORT) {
+		hba->ahit = FIELD_PREP(UFSHCI_AHIBERN8_TIMER_MASK, 150) |
+			    FIELD_PREP(UFSHCI_AHIBERN8_SCALE_MASK, 3);
+	}
 
 	/* Hold auto suspend until async scan completes */
 	pm_runtime_get_sync(dev);

drivers/scsi/ufs/ufshcd.h

···
 	struct device_attribute spm_lvl_attr;
 	int pm_op_in_progress;
 
+	/* Auto-Hibernate Idle Timer register value */
+	u32 ahit;
+
 	struct ufshcd_lrb *lrb;
 	unsigned long lrb_in_use;
 

drivers/scsi/ufs/ufshci.h

···
 enum {
 	MASK_TRANSFER_REQUESTS_SLOTS		= 0x0000001F,
 	MASK_TASK_MANAGEMENT_REQUEST_SLOTS	= 0x00070000,
+	MASK_AUTO_HIBERN8_SUPPORT		= 0x00800000,
 	MASK_64_ADDRESSING_SUPPORT		= 0x01000000,
 	MASK_OUT_OF_ORDER_DATA_DELIVERY_SUPPORT	= 0x02000000,
 	MASK_UIC_DME_TEST_MODE_SUPPORT		= 0x04000000,
···
  */
 #define MANUFACTURE_ID_MASK	UFS_MASK(0xFFFF, 0)
 #define PRODUCT_ID_MASK		UFS_MASK(0xFFFF, 16)
+
+/* AHIT - Auto-Hibernate Idle Timer */
+#define UFSHCI_AHIBERN8_TIMER_MASK		GENMASK(9, 0)
+#define UFSHCI_AHIBERN8_SCALE_MASK		GENMASK(12, 10)
+#define UFSHCI_AHIBERN8_SCALE_FACTOR		10
+#define UFSHCI_AHIBERN8_MAX			(1023 * 100000)
 
 /*
  * IS - Interrupt Status - 20h