thermal: int340x: processor_thermal: Support power floor notifications

When the hardware reduces the power to the minimum possible, the power
floor is notified via an interrupt.

This can happen when user space requests a power limit via powercap RAPL
interface, which forces the system to enter to the lowest power. This
power floor indication can be used as a hint to resort to other methods
of reducing power than via RAPL power limit.

Before power floor status can be read or the firmware can trigger
notifications regarding it, it needs to be configured via a mailbox
command. The actual power floor status is read via bit 39 of MMIO
offset 0x5B18 of the processor thermal PCI device.

To show the current power floor status and get notification
on a sysfs attribute, add 2 new attributes to
/sys/bus/pci/devices/0000\:00\:04.0/power_limits/

power_floor_enable : This attribute is present when power floor
 notifications are supported. This attribute allows to enable/disable
 power floor notifications.

power_floor_status : This attribute is present when power floor
 notifications are supported. When enabled via power_floor_enable, this
 attribute shows the current power floor status.

The power floor implementation provides interfaces which are called
from the sysfs callbacks to enable/disable and read power floor
status. It also provides two additional interfaces to check if the
current processor thermal device interrupt is for power floor status
and to send notifications to user space.

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
[ rjw: Changelog and documentation changes edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Documentation/driver-api/thermal/intel_dptf.rst

@@ -164,6 +164,16 @@ ABI.
 ``power_limit_1_tmax_us`` (RO)
 	Maximum powercap sysfs constraint_1_time_window_us for Intel RAPL
 
+``power_floor_status`` (RO)
+	When set to 1, the power floor of the system in the current
+	configuration has been reached.  It needs to be reconfigured to allow
+	power to be reduced any further.
+
+``power_floor_enable`` (RW)
+	When set to 1, enable reading and notification of the power floor
+	status. Notifications are triggered for the power_floor_status
+	attribute value changes.
+
 :file:`/sys/bus/pci/devices/0000\:00\:04.0/`
 
 ``tcc_offset_degree_celsius`` (RW)

drivers/thermal/intel/int340x_thermal/Makefile

@@ -12,5 +12,6 @@ obj-$(CONFIG_INT340X_THERMAL)	+= processor_thermal_rfim.o
 obj-$(CONFIG_INT340X_THERMAL)	+= processor_thermal_mbox.o
 obj-$(CONFIG_INT340X_THERMAL)	+= processor_thermal_wt_req.o
 obj-$(CONFIG_INT340X_THERMAL)	+= processor_thermal_wt_hint.o
+obj-$(CONFIG_INT340X_THERMAL)	+= processor_thermal_power_floor.o
 obj-$(CONFIG_INT3406_THERMAL)	+= int3406_thermal.o
 obj-$(CONFIG_ACPI_THERMAL_REL)	+= acpi_thermal_rel.o

drivers/thermal/intel/int340x_thermal/processor_thermal_device.c

@@ -26,6 +26,48 @@ static ssize_t power_limit_##index##_##suffix##_show(struct device *dev, \
 	(unsigned long)proc_dev->power_limits[index].suffix * 1000); \
 }
 
+static ssize_t power_floor_status_show(struct device *dev,
+				       struct device_attribute *attr,
+				       char *buf)
+{
+	struct proc_thermal_device *proc_dev = dev_get_drvdata(dev);
+	int ret;
+
+	ret = proc_thermal_read_power_floor_status(proc_dev);
+
+	return sysfs_emit(buf, "%d\n", ret);
+}
+
+static ssize_t power_floor_enable_show(struct device *dev,
+				       struct device_attribute *attr,
+				       char *buf)
+{
+	struct proc_thermal_device *proc_dev = dev_get_drvdata(dev);
+	bool ret;
+
+	ret = proc_thermal_power_floor_get_state(proc_dev);
+
+	return sysfs_emit(buf, "%d\n", ret);
+}
+
+static ssize_t power_floor_enable_store(struct device *dev,
+					struct device_attribute *attr,
+					const char *buf, size_t count)
+{
+	struct proc_thermal_device *proc_dev = dev_get_drvdata(dev);
+	u8 state;
+	int ret;
+
+	if (kstrtou8(buf, 0, &state))
+		return -EINVAL;
+
+	ret = proc_thermal_power_floor_set_state(proc_dev, !!state);
+	if (ret)
+		return ret;
+
+	return count;
+}
+
 POWER_LIMIT_SHOW(0, min_uw)
 POWER_LIMIT_SHOW(0, max_uw)
 POWER_LIMIT_SHOW(0, step_uw)
@@ -50,6 +92,9 @@ static DEVICE_ATTR_RO(power_limit_1_step_uw);
 static DEVICE_ATTR_RO(power_limit_1_tmin_us);
 static DEVICE_ATTR_RO(power_limit_1_tmax_us);
 
+static DEVICE_ATTR_RO(power_floor_status);
+static DEVICE_ATTR_RW(power_floor_enable);
+
 static struct attribute *power_limit_attrs[] = {
 	&dev_attr_power_limit_0_min_uw.attr,
 	&dev_attr_power_limit_1_min_uw.attr,
@@ -61,12 +106,30 @@ static struct attribute *power_limit_attrs[] = {
 	&dev_attr_power_limit_1_tmin_us.attr,
 	&dev_attr_power_limit_0_tmax_us.attr,
 	&dev_attr_power_limit_1_tmax_us.attr,
+	&dev_attr_power_floor_status.attr,
+	&dev_attr_power_floor_enable.attr,
 	NULL
 };
 
+static umode_t power_limit_attr_visible(struct kobject *kobj, struct attribute *attr, int unused)
+{
+	struct device *dev = kobj_to_dev(kobj);
+	struct proc_thermal_device *proc_dev;
+
+	if (attr != &dev_attr_power_floor_status.attr && attr != &dev_attr_power_floor_enable.attr)
+		return attr->mode;
+
+	proc_dev = dev_get_drvdata(dev);
+	if (!proc_dev || !(proc_dev->mmio_feature_mask & PROC_THERMAL_FEATURE_POWER_FLOOR))
+		return 0;
+
+	return attr->mode;
+}
+
 static const struct attribute_group power_limit_attribute_group = {
 	.attrs = power_limit_attrs,
-	.name = "power_limits"
+	.name = "power_limits",
+	.is_visible = power_limit_attr_visible,
 };
 
 static ssize_t tcc_offset_degree_celsius_show(struct device *dev,
@@ -380,6 +443,9 @@ void proc_thermal_mmio_remove(struct pci_dev *pdev, struct proc_thermal_device *
 	    proc_priv->mmio_feature_mask & PROC_THERMAL_FEATURE_DVFS)
 		proc_thermal_rfim_remove(pdev);
 
+	if (proc_priv->mmio_feature_mask & PROC_THERMAL_FEATURE_POWER_FLOOR)
+		proc_thermal_power_floor_set_state(proc_priv, false);
+
 	if (proc_priv->mmio_feature_mask & PROC_THERMAL_FEATURE_WT_REQ)
 		proc_thermal_wt_req_remove(pdev);
 	else if (proc_priv->mmio_feature_mask & PROC_THERMAL_FEATURE_WT_HINT)

drivers/thermal/intel/int340x_thermal/processor_thermal_device.h

@@ -63,6 +63,7 @@ struct rapl_mmio_regs {
 #define PROC_THERMAL_FEATURE_WT_REQ	0x08
 #define PROC_THERMAL_FEATURE_DLVR	0x10
 #define PROC_THERMAL_FEATURE_WT_HINT	0x20
+#define PROC_THERMAL_FEATURE_POWER_FLOOR	0x40
 
 #if IS_ENABLED(CONFIG_PROC_THERMAL_MMIO_RAPL)
 int proc_thermal_rapl_add(struct pci_dev *pdev, struct proc_thermal_device *proc_priv);
@@ -94,6 +95,13 @@ void proc_thermal_wt_req_remove(struct pci_dev *pdev);
 #define SOC_WT_RES_INT_STATUS_OFFSET	0x5B18
 #define SOC_WT_RES_INT_STATUS_MASK	GENMASK_ULL(3, 2)
 
+int proc_thermal_read_power_floor_status(struct proc_thermal_device *proc_priv);
+int proc_thermal_power_floor_set_state(struct proc_thermal_device *proc_priv, bool enable);
+bool proc_thermal_power_floor_get_state(struct proc_thermal_device *proc_priv);
+void proc_thermal_power_floor_intr_callback(struct pci_dev *pdev,
+					    struct proc_thermal_device *proc_priv);
+bool proc_thermal_check_power_floor_intr(struct proc_thermal_device *proc_priv);
+
 int processor_thermal_send_mbox_read_cmd(struct pci_dev *pdev, u16 id, u64 *resp);
 int processor_thermal_send_mbox_write_cmd(struct pci_dev *pdev, u16 id, u32 data);
 int processor_thermal_mbox_interrupt_config(struct pci_dev *pdev, bool enable, int enable_bit,

drivers/thermal/intel/int340x_thermal/processor_thermal_power_floor.c

@@ -0,0 +1,126 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Processor thermal device module for registering and processing
+ * power floor. When the hardware reduces the power to the minimum
+ * possible, the power floor is notified via an interrupt.
+ *
+ * Operation:
+ * When user space enables power floor reporting:
+ * - Use mailbox to:
+ *	Enable processor thermal device interrupt
+ *
+ * - Current status of power floor is read from offset 0x5B18
+ *   bit 39.
+ *
+ * Two interface functions are provided to call when there is a
+ * thermal device interrupt:
+ * - proc_thermal_power_floor_intr():
+ *	Check if the interrupt is for change in power floor.
+ *	Called from interrupt context.
+ *
+ * - proc_thermal_power_floor_intr_callback():
+ *	Callback for interrupt processing in thread context. This involves
+ *	sending notification to user space that there is a change in the
+ *	power floor status.
+ *
+ * Copyright (c) 2023, Intel Corporation.
+ */
+
+#include <linux/pci.h>
+#include "processor_thermal_device.h"
+
+#define SOC_POWER_FLOOR_STATUS		BIT(39)
+#define SOC_POWER_FLOOR_SHIFT		39
+
+#define SOC_POWER_FLOOR_INT_ENABLE_BIT	31
+#define SOC_POWER_FLOOR_INT_ACTIVE	BIT(3)
+
+int proc_thermal_read_power_floor_status(struct proc_thermal_device *proc_priv)
+{
+	u64 status = 0;
+
+	status = readq(proc_priv->mmio_base + SOC_WT_RES_INT_STATUS_OFFSET);
+	return (status & SOC_POWER_FLOOR_STATUS) >> SOC_POWER_FLOOR_SHIFT;
+}
+EXPORT_SYMBOL_NS_GPL(proc_thermal_read_power_floor_status, INT340X_THERMAL);
+
+static bool enable_state;
+static DEFINE_MUTEX(pf_lock);
+
+int proc_thermal_power_floor_set_state(struct proc_thermal_device *proc_priv, bool enable)
+{
+	int ret = 0;
+
+	mutex_lock(&pf_lock);
+	if (enable_state == enable)
+		goto pf_unlock;
+
+	/*
+	 * Time window parameter is not applicable to power floor interrupt configuration.
+	 * Hence use -1 for time window.
+	 */
+	ret = processor_thermal_mbox_interrupt_config(to_pci_dev(proc_priv->dev), enable,
+						      SOC_POWER_FLOOR_INT_ENABLE_BIT, -1);
+	if (!ret)
+		enable_state = enable;
+
+pf_unlock:
+	mutex_unlock(&pf_lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_NS_GPL(proc_thermal_power_floor_set_state, INT340X_THERMAL);
+
+bool proc_thermal_power_floor_get_state(struct proc_thermal_device *proc_priv)
+{
+	return enable_state;
+}
+EXPORT_SYMBOL_NS_GPL(proc_thermal_power_floor_get_state, INT340X_THERMAL);
+
+/**
+ * proc_thermal_check_power_floor_intr() - Check power floor interrupt.
+ * @proc_priv: Processor thermal device instance.
+ *
+ * Callback to check if the interrupt for power floor is active.
+ *
+ * Context: Called from interrupt context.
+ *
+ * Return: true if power floor is active, false when not active.
+ */
+bool proc_thermal_check_power_floor_intr(struct proc_thermal_device *proc_priv)
+{
+	u64 int_status;
+
+	int_status = readq(proc_priv->mmio_base + SOC_WT_RES_INT_STATUS_OFFSET);
+	return !!(int_status & SOC_POWER_FLOOR_INT_ACTIVE);
+}
+EXPORT_SYMBOL_NS_GPL(proc_thermal_check_power_floor_intr, INT340X_THERMAL);
+
+/**
+ * proc_thermal_power_floor_intr_callback() - Process power floor notification
+ * @pdev:	PCI device instance
+ * @proc_priv: Processor thermal device instance.
+ *
+ * Check if the power floor interrupt is active, if active send notification to
+ * user space for the attribute "power_limits", so that user can read the attribute
+ * and take action.
+ *
+ * Context: Called from interrupt thread context.
+ *
+ * Return: None.
+ */
+void proc_thermal_power_floor_intr_callback(struct pci_dev *pdev,
+					    struct proc_thermal_device *proc_priv)
+{
+	u64 status;
+
+	status = readq(proc_priv->mmio_base + SOC_WT_RES_INT_STATUS_OFFSET);
+	if (!(status & SOC_POWER_FLOOR_INT_ACTIVE))
+		return;
+
+	sysfs_notify(&pdev->dev.kobj, "power_limits", "power_floor_status");
+}
+EXPORT_SYMBOL_NS_GPL(proc_thermal_power_floor_intr_callback, INT340X_THERMAL);
+
+MODULE_IMPORT_NS(INT340X_THERMAL);
+MODULE_LICENSE("GPL");