drm/panthor: Add the devfreq logical block

Every thing related to devfreq in placed in panthor_devfreq.c, and
helpers that can be called by other logical blocks are exposed through
panthor_devfreq.h.

This implementation is loosely based on the panfrost implementation,
the only difference being that we don't count device users, because
the idle/active state will be managed by the scheduler logic.

v6:
- Add Maxime's and Heiko's acks
- Keep header inclusion alphabetically ordered

v4:
- Add Clément's A-b for the relicensing

v3:
- Add acks for the MIT/GPL2 relicensing

v2:
- Added in v2

Cc: Clément Péron <peron.clem@gmail.com> # MIT+GPL2 relicensing
Reviewed-by: Steven Price <steven.price@arm.com>
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Acked-by: Steven Price <steven.price@arm.com> # MIT+GPL2 relicensing,Arm
Acked-by: Grant Likely <grant.likely@linaro.org> # MIT+GPL2 relicensing,Linaro
Acked-by: Boris Brezillon <boris.brezillon@collabora.com> # MIT+GPL2 relicensing,Collabora
Acked-by: Clément Péron <peron.clem@gmail.com> # MIT+GPL2 relicensing
Acked-by: Maxime Ripard <mripard@kernel.org>
Acked-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20240229162230.2634044-7-boris.brezillon@collabora.com

drivers/gpu/drm/panthor/panthor_devfreq.c

@@ -0,0 +1,283 @@
+// SPDX-License-Identifier: GPL-2.0 or MIT
+/* Copyright 2019 Collabora ltd. */
+
+#include <linux/clk.h>
+#include <linux/devfreq.h>
+#include <linux/devfreq_cooling.h>
+#include <linux/platform_device.h>
+#include <linux/pm_opp.h>
+
+#include <drm/drm_managed.h>
+
+#include "panthor_devfreq.h"
+#include "panthor_device.h"
+
+/**
+ * struct panthor_devfreq - Device frequency management
+ */
+struct panthor_devfreq {
+	/** @devfreq: devfreq device. */
+	struct devfreq *devfreq;
+
+	/** @gov_data: Governor data. */
+	struct devfreq_simple_ondemand_data gov_data;
+
+	/** @busy_time: Busy time. */
+	ktime_t busy_time;
+
+	/** @idle_time: Idle time. */
+	ktime_t idle_time;
+
+	/** @time_last_update: Last update time. */
+	ktime_t time_last_update;
+
+	/** @last_busy_state: True if the GPU was busy last time we updated the state. */
+	bool last_busy_state;
+
+	/*
+	 * @lock: Lock used to protect busy_time, idle_time, time_last_update and
+	 * last_busy_state.
+	 *
+	 * These fields can be accessed concurrently by panthor_devfreq_get_dev_status()
+	 * and panthor_devfreq_record_{busy,idle}().
+	 */
+	spinlock_t lock;
+};
+
+static void panthor_devfreq_update_utilization(struct panthor_devfreq *pdevfreq)
+{
+	ktime_t now, last;
+
+	now = ktime_get();
+	last = pdevfreq->time_last_update;
+
+	if (pdevfreq->last_busy_state)
+		pdevfreq->busy_time += ktime_sub(now, last);
+	else
+		pdevfreq->idle_time += ktime_sub(now, last);
+
+	pdevfreq->time_last_update = now;
+}
+
+static int panthor_devfreq_target(struct device *dev, unsigned long *freq,
+				  u32 flags)
+{
+	struct dev_pm_opp *opp;
+
+	opp = devfreq_recommended_opp(dev, freq, flags);
+	if (IS_ERR(opp))
+		return PTR_ERR(opp);
+	dev_pm_opp_put(opp);
+
+	return dev_pm_opp_set_rate(dev, *freq);
+}
+
+static void panthor_devfreq_reset(struct panthor_devfreq *pdevfreq)
+{
+	pdevfreq->busy_time = 0;
+	pdevfreq->idle_time = 0;
+	pdevfreq->time_last_update = ktime_get();
+}
+
+static int panthor_devfreq_get_dev_status(struct device *dev,
+					  struct devfreq_dev_status *status)
+{
+	struct panthor_device *ptdev = dev_get_drvdata(dev);
+	struct panthor_devfreq *pdevfreq = ptdev->devfreq;
+	unsigned long irqflags;
+
+	status->current_frequency = clk_get_rate(ptdev->clks.core);
+
+	spin_lock_irqsave(&pdevfreq->lock, irqflags);
+
+	panthor_devfreq_update_utilization(pdevfreq);
+
+	status->total_time = ktime_to_ns(ktime_add(pdevfreq->busy_time,
+						   pdevfreq->idle_time));
+
+	status->busy_time = ktime_to_ns(pdevfreq->busy_time);
+
+	panthor_devfreq_reset(pdevfreq);
+
+	spin_unlock_irqrestore(&pdevfreq->lock, irqflags);
+
+	drm_dbg(&ptdev->base, "busy %lu total %lu %lu %% freq %lu MHz\n",
+		status->busy_time, status->total_time,
+		status->busy_time / (status->total_time / 100),
+		status->current_frequency / 1000 / 1000);
+
+	return 0;
+}
+
+static struct devfreq_dev_profile panthor_devfreq_profile = {
+	.timer = DEVFREQ_TIMER_DELAYED,
+	.polling_ms = 50, /* ~3 frames */
+	.target = panthor_devfreq_target,
+	.get_dev_status = panthor_devfreq_get_dev_status,
+};
+
+int panthor_devfreq_init(struct panthor_device *ptdev)
+{
+	/* There's actually 2 regulators (mali and sram), but the OPP core only
+	 * supports one.
+	 *
+	 * We assume the sram regulator is coupled with the mali one and let
+	 * the coupling logic deal with voltage updates.
+	 */
+	static const char * const reg_names[] = { "mali", NULL };
+	struct thermal_cooling_device *cooling;
+	struct device *dev = ptdev->base.dev;
+	struct panthor_devfreq *pdevfreq;
+	struct dev_pm_opp *opp;
+	unsigned long cur_freq;
+	int ret;
+
+	pdevfreq = drmm_kzalloc(&ptdev->base, sizeof(*ptdev->devfreq), GFP_KERNEL);
+	if (!pdevfreq)
+		return -ENOMEM;
+
+	ptdev->devfreq = pdevfreq;
+
+	ret = devm_pm_opp_set_regulators(dev, reg_names);
+	if (ret) {
+		if (ret != -EPROBE_DEFER)
+			DRM_DEV_ERROR(dev, "Couldn't set OPP regulators\n");
+
+		return ret;
+	}
+
+	ret = devm_pm_opp_of_add_table(dev);
+	if (ret)
+		return ret;
+
+	spin_lock_init(&pdevfreq->lock);
+
+	panthor_devfreq_reset(pdevfreq);
+
+	cur_freq = clk_get_rate(ptdev->clks.core);
+
+	opp = devfreq_recommended_opp(dev, &cur_freq, 0);
+	if (IS_ERR(opp))
+		return PTR_ERR(opp);
+
+	panthor_devfreq_profile.initial_freq = cur_freq;
+
+	/* Regulator coupling only takes care of synchronizing/balancing voltage
+	 * updates, but the coupled regulator needs to be enabled manually.
+	 *
+	 * We use devm_regulator_get_enable_optional() and keep the sram supply
+	 * enabled until the device is removed, just like we do for the mali
+	 * supply, which is enabled when dev_pm_opp_set_opp(dev, opp) is called,
+	 * and disabled when the opp_table is torn down, using the devm action.
+	 *
+	 * If we really care about disabling regulators on suspend, we should:
+	 * - use devm_regulator_get_optional() here
+	 * - call dev_pm_opp_set_opp(dev, NULL) before leaving this function
+	 *   (this disables the regulator passed to the OPP layer)
+	 * - call dev_pm_opp_set_opp(dev, NULL) and
+	 *   regulator_disable(ptdev->regulators.sram) in
+	 *   panthor_devfreq_suspend()
+	 * - call dev_pm_opp_set_opp(dev, default_opp) and
+	 *   regulator_enable(ptdev->regulators.sram) in
+	 *   panthor_devfreq_resume()
+	 *
+	 * But without knowing if it's beneficial or not (in term of power
+	 * consumption), or how much it slows down the suspend/resume steps,
+	 * let's just keep regulators enabled for the device lifetime.
+	 */
+	ret = devm_regulator_get_enable_optional(dev, "sram");
+	if (ret && ret != -ENODEV) {
+		if (ret != -EPROBE_DEFER)
+			DRM_DEV_ERROR(dev, "Couldn't retrieve/enable sram supply\n");
+		return ret;
+	}
+
+	/*
+	 * Set the recommend OPP this will enable and configure the regulator
+	 * if any and will avoid a switch off by regulator_late_cleanup()
+	 */
+	ret = dev_pm_opp_set_opp(dev, opp);
+	if (ret) {
+		DRM_DEV_ERROR(dev, "Couldn't set recommended OPP\n");
+		return ret;
+	}
+
+	dev_pm_opp_put(opp);
+
+	/*
+	 * Setup default thresholds for the simple_ondemand governor.
+	 * The values are chosen based on experiments.
+	 */
+	pdevfreq->gov_data.upthreshold = 45;
+	pdevfreq->gov_data.downdifferential = 5;
+
+	pdevfreq->devfreq = devm_devfreq_add_device(dev, &panthor_devfreq_profile,
+						    DEVFREQ_GOV_SIMPLE_ONDEMAND,
+						    &pdevfreq->gov_data);
+	if (IS_ERR(pdevfreq->devfreq)) {
+		DRM_DEV_ERROR(dev, "Couldn't initialize GPU devfreq\n");
+		ret = PTR_ERR(pdevfreq->devfreq);
+		pdevfreq->devfreq = NULL;
+		return ret;
+	}
+
+	cooling = devfreq_cooling_em_register(pdevfreq->devfreq, NULL);
+	if (IS_ERR(cooling))
+		DRM_DEV_INFO(dev, "Failed to register cooling device\n");
+
+	return 0;
+}
+
+int panthor_devfreq_resume(struct panthor_device *ptdev)
+{
+	struct panthor_devfreq *pdevfreq = ptdev->devfreq;
+
+	if (!pdevfreq->devfreq)
+		return 0;
+
+	panthor_devfreq_reset(pdevfreq);
+
+	return devfreq_resume_device(pdevfreq->devfreq);
+}
+
+int panthor_devfreq_suspend(struct panthor_device *ptdev)
+{
+	struct panthor_devfreq *pdevfreq = ptdev->devfreq;
+
+	if (!pdevfreq->devfreq)
+		return 0;
+
+	return devfreq_suspend_device(pdevfreq->devfreq);
+}
+
+void panthor_devfreq_record_busy(struct panthor_device *ptdev)
+{
+	struct panthor_devfreq *pdevfreq = ptdev->devfreq;
+	unsigned long irqflags;
+
+	if (!pdevfreq->devfreq)
+		return;
+
+	spin_lock_irqsave(&pdevfreq->lock, irqflags);
+
+	panthor_devfreq_update_utilization(pdevfreq);
+	pdevfreq->last_busy_state = true;
+
+	spin_unlock_irqrestore(&pdevfreq->lock, irqflags);
+}
+
+void panthor_devfreq_record_idle(struct panthor_device *ptdev)
+{
+	struct panthor_devfreq *pdevfreq = ptdev->devfreq;
+	unsigned long irqflags;
+
+	if (!pdevfreq->devfreq)
+		return;
+
+	spin_lock_irqsave(&pdevfreq->lock, irqflags);
+
+	panthor_devfreq_update_utilization(pdevfreq);
+	pdevfreq->last_busy_state = false;
+
+	spin_unlock_irqrestore(&pdevfreq->lock, irqflags);
+}

drivers/gpu/drm/panthor/panthor_devfreq.h

@@ -0,0 +1,21 @@
+/* SPDX-License-Identifier: GPL-2.0 or MIT */
+/* Copyright 2019 Collabora ltd. */
+
+#ifndef __PANTHOR_DEVFREQ_H__
+#define __PANTHOR_DEVFREQ_H__
+
+struct devfreq;
+struct thermal_cooling_device;
+
+struct panthor_device;
+struct panthor_devfreq;
+
+int panthor_devfreq_init(struct panthor_device *ptdev);
+
+int panthor_devfreq_resume(struct panthor_device *ptdev);
+int panthor_devfreq_suspend(struct panthor_device *ptdev);
+
+void panthor_devfreq_record_busy(struct panthor_device *ptdev);
+void panthor_devfreq_record_idle(struct panthor_device *ptdev);
+
+#endif /* __PANTHOR_DEVFREQ_H__ */