[PATCH 3/3] drm/i915/hwmon: Expose power1_max_enable

[Ashutosh Dixit]

On ATSM the PL1 power limit is disabled at power up. The previous uapi
assumed that the PL1 limit is always enabled and therefore did not have a
notion of a disabled PL1 limit. This results in erroneous PL1 limit values
when PL1 limit is disabled. For example at power up, the disabled ATSM PL1
limit is shown as 0 which means a low PL1 limit whereas the limit being
disabled actually implies a high effective PL1 limit value.

To get round this problem, expose power1_max_enable as a custom hwmon
attribute. power1_max_enable can be used in conjunction with power1_max to
interpret power1_max (PL1 limit) values correctly. It can also be used to
enable/disable the PL1 power limit.

Signed-off-by: Ashutosh Dixit <ashutosh.dixit at intel.com>
---
 .../ABI/testing/sysfs-driver-intel-i915-hwmon |  7 +++
 drivers/gpu/drm/i915/i915_hwmon.c             | 48 +++++++++++++++++--
 2 files changed, 51 insertions(+), 4 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-driver-intel-i915-hwmon b/Documentation/ABI/testing/sysfs-driver-intel-i915-hwmon
index 2d6a472eef885..edd94a44b4570 100644
--- a/Documentation/ABI/testing/sysfs-driver-intel-i915-hwmon
+++ b/Documentation/ABI/testing/sysfs-driver-intel-i915-hwmon
@@ -18,6 +18,13 @@ Description:	RW. Card reactive sustained  (PL1/Tau) power limit in microwatts.
 
 		Only supported for particular Intel i915 graphics platforms.
 
+What:		/sys/devices/.../hwmon/hwmon<i>/power1_max_enable
+Date:		May 2023
+KernelVersion:	6.3
+Contact:	intel-gfx at lists.freedesktop.org
+Description:	RW. Enable/disable the PL1 power limit (power1_max).
+
+		Only supported for particular Intel i915 graphics platforms.
 What:		/sys/devices/.../hwmon/hwmon<i>/power1_rated_max
 Date:		February 2023
 KernelVersion:	6.2
diff --git a/drivers/gpu/drm/i915/i915_hwmon.c b/drivers/gpu/drm/i915/i915_hwmon.c
index 7c20a6f47b92e..5665869d8602b 100644
--- a/drivers/gpu/drm/i915/i915_hwmon.c
+++ b/drivers/gpu/drm/i915/i915_hwmon.c
@@ -230,13 +230,52 @@ hwm_power1_max_interval_store(struct device *dev,
 					    PKG_PWR_LIM_1_TIME, rxy);
 	return count;
 }
+static SENSOR_DEVICE_ATTR_RW(power1_max_interval, hwm_power1_max_interval, 0);
 
-static SENSOR_DEVICE_ATTR(power1_max_interval, 0664,
-			  hwm_power1_max_interval_show,
-			  hwm_power1_max_interval_store, 0);
+static ssize_t
+hwm_power1_max_enable_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct hwm_drvdata *ddat = dev_get_drvdata(dev);
+	intel_wakeref_t wakeref;
+	u32 r;
+
+	with_intel_runtime_pm(ddat->uncore->rpm, wakeref)
+		r = intel_uncore_read(ddat->uncore, ddat->hwmon->rg.pkg_rapl_limit);
+
+	return sysfs_emit(buf, "%u\n", !!(r & PKG_PWR_LIM_1_EN));
+}
+
+static ssize_t
+hwm_power1_max_enable_store(struct device *dev, struct device_attribute *attr,
+			    const char *buf, size_t count)
+{
+	struct hwm_drvdata *ddat = dev_get_drvdata(dev);
+	intel_wakeref_t wakeref;
+	u32 en, r;
+	bool _en;
+	int ret;
+
+	ret = kstrtobool(buf, &_en);
+	if (ret)
+		return ret;
+
+	en = REG_FIELD_PREP(PKG_PWR_LIM_1_EN, _en);
+	hwm_locked_with_pm_intel_uncore_rmw(ddat, ddat->hwmon->rg.pkg_rapl_limit,
+					    PKG_PWR_LIM_1_EN, en);
+
+	/* Verify, because PL1 limit cannot be disabled on all platforms */
+	with_intel_runtime_pm(ddat->uncore->rpm, wakeref)
+		r = intel_uncore_read(ddat->uncore, ddat->hwmon->rg.pkg_rapl_limit);
+	if ((r & PKG_PWR_LIM_1_EN) != en)
+		return -EPERM;
+
+	return count;
+}
+static SENSOR_DEVICE_ATTR_RW(power1_max_enable, hwm_power1_max_enable, 0);
 
 static struct attribute *hwm_attributes[] = {
 	&sensor_dev_attr_power1_max_interval.dev_attr.attr,
+	&sensor_dev_attr_power1_max_enable.dev_attr.attr,
 	NULL
 };
 
@@ -247,7 +286,8 @@ static umode_t hwm_attributes_visible(struct kobject *kobj,
 	struct hwm_drvdata *ddat = dev_get_drvdata(dev);
 	struct i915_hwmon *hwmon = ddat->hwmon;
 
-	if (attr == &sensor_dev_attr_power1_max_interval.dev_attr.attr)
+	if (attr == &sensor_dev_attr_power1_max_interval.dev_attr.attr ||
+	    attr == &sensor_dev_attr_power1_max_enable.dev_attr.attr)
 		return i915_mmio_reg_valid(hwmon->rg.pkg_rapl_limit) ? attr->mode : 0;
 
 	return 0;
-- 
2.38.0