linux-kernel - [PATCH] drm/lima: add governor data with pre-defined thresholds

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Date:   Mon, 25 Jan 2021 08:18:04 +0000
From:   Christian Hewitt <christianshewitt@...il.com>
To:     Qiang Yu <yuq825@...il.com>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel@...ts.freedesktop.org, lima@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Cc:     Christian Hewitt <christianshewitt@...il.com>,
        Lukasz Luba <lukasz.luba@....com>,
        Steven Price <steven.price@....com>
Subject: [PATCH] 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@...il.com>
---
I have been using Kodi as my test application. If you scroll in library
views with hundreds of list items and the panfrost values the slow GPU
ramp up is quite noticeable and the GUI feels sluggish. As everything
lima runs on is inherently slower than panfrost using devices I believe
it's better to ramp up to max freq quicker.

 drivers/gpu/drm/lima/lima_devfreq.c | 10 +++++++++-
 drivers/gpu/drm/lima/lima_devfreq.h |  2 ++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/lima/lima_devfreq.c b/drivers/gpu/drm/lima/lima_devfreq.c
index 5686ad4aaf7c..c9854315a0b5 100644
--- a/drivers/gpu/drm/lima/lima_devfreq.c
+++ b/drivers/gpu/drm/lima/lima_devfreq.c
@@ -163,8 +163,16 @@ 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 = 20;
+	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);
diff --git a/drivers/gpu/drm/lima/lima_devfreq.h b/drivers/gpu/drm/lima/lima_devfreq.h
index 2d9b3008ce77..b0c7c736e81a 100644
--- a/drivers/gpu/drm/lima/lima_devfreq.h
+++ b/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;
-- 
2.17.1