drm/lima: add governor data with pre-defined thresholds

This patch adapts the panfrost pre-defined thresholds change [0] to the
lima driver to improve real-world performance. The upthreshold value has
been set to ramp GPU frequency to max freq faster (compared to panfrost)
to compensate for the lower overall performance of utgard devices.

[0] https://patchwork.kernel.org/project/dri-devel/patch/20210121170445.19761-1-lukasz.luba@arm.com/Signed-off-by: Christian Hewitt <christianshewitt@gmail.com>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
Signed-off-by: Qiang Yu <yuq825@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210127194047.21462-1-christianshewitt@gmail.com

drivers/gpu/drm/lima/lima_devfreq.c

@@ -164,8 +164,16 @@ int lima_devfreq_init(struct lima_device *ldev)
 	lima_devfreq_profile.initial_freq = cur_freq;
 	dev_pm_opp_put(opp);
 
+	/*
+	 * Setup default thresholds for the simple_ondemand governor.
+	 * The values are chosen based on experiments.
+	 */
+	ldevfreq->gov_data.upthreshold = 30;
+	ldevfreq->gov_data.downdifferential = 5;
+
 	devfreq = devm_devfreq_add_device(dev, &lima_devfreq_profile,
-					  DEVFREQ_GOV_SIMPLE_ONDEMAND, NULL);
+					  DEVFREQ_GOV_SIMPLE_ONDEMAND,
+					  &ldevfreq->gov_data);
 	if (IS_ERR(devfreq)) {
 		dev_err(dev, "Couldn't initialize GPU devfreq\n");
 		ret = PTR_ERR(devfreq);

drivers/gpu/drm/lima/lima_devfreq.h

@@ -4,6 +4,7 @@
 #ifndef __LIMA_DEVFREQ_H__
 #define __LIMA_DEVFREQ_H__
 
+#include <linux/devfreq.h>
 #include <linux/spinlock.h>
 #include <linux/ktime.h>
 
@@ -18,6 +19,7 @@ struct lima_devfreq {
 	struct opp_table *clkname_opp_table;
 	struct opp_table *regulators_opp_table;
 	struct thermal_cooling_device *cooling;
+	struct devfreq_simple_ondemand_data gov_data;
 
 	ktime_t busy_time;
 	ktime_t idle_time;