linux-kernel - [PATCH v7 4/5] drm/panthor: Use existing OPP table if present

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Message-Id: <20251015-mt8196-gpufreq-v7-4-0a6435da2080@collabora.com>
Date: Wed, 15 Oct 2025 10:50:03 +0200
From: Nicolas Frattaroli <nicolas.frattaroli@...labora.com>
To: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, 
 Boris Brezillon <boris.brezillon@...labora.com>, 
 Jassi Brar <jassisinghbrar@...il.com>, Chia-I Wu <olvaffe@...il.com>, 
 Chen-Yu Tsai <wenst@...omium.org>, Steven Price <steven.price@....com>, 
 Liviu Dudau <liviu.dudau@....com>, 
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, 
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
 Conor Dooley <conor+dt@...nel.org>, 
 Matthias Brugger <matthias.bgg@...il.com>, Kees Cook <kees@...nel.org>, 
 "Gustavo A. R. Silva" <gustavoars@...nel.org>, 
 Ulf Hansson <ulf.hansson@...aro.org>
Cc: kernel@...labora.com, dri-devel@...ts.freedesktop.org, 
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
 linux-arm-kernel@...ts.infradead.org, linux-mediatek@...ts.infradead.org, 
 linux-hardening@...r.kernel.org, linux-pm@...r.kernel.org, 
 Nicolas Frattaroli <nicolas.frattaroli@...labora.com>
Subject: [PATCH v7 4/5] drm/panthor: Use existing OPP table if present

On SoCs where the GPU's power-domain is in charge of setting performance
levels, the OPP table of the GPU node will have already been populated
during said power-domain's attach_dev operation.

To avoid initialising an OPP table twice, only set the OPP regulator and
the OPPs from DT if there's no OPP table present.

Reviewed-by: Chia-I Wu <olvaffe@...il.com>
Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@...labora.com>
---
 drivers/gpu/drm/panthor/panthor_devfreq.c | 32 ++++++++++++++++++++++---------
 1 file changed, 23 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/panthor/panthor_devfreq.c b/drivers/gpu/drm/panthor/panthor_devfreq.c
index a6dca599f0a5..ec63e27f4883 100644
--- a/drivers/gpu/drm/panthor/panthor_devfreq.c
+++ b/drivers/gpu/drm/panthor/panthor_devfreq.c
@@ -141,6 +141,7 @@ int panthor_devfreq_init(struct panthor_device *ptdev)
 	struct thermal_cooling_device *cooling;
 	struct device *dev = ptdev->base.dev;
 	struct panthor_devfreq *pdevfreq;
+	struct opp_table *table;
 	struct dev_pm_opp *opp;
 	unsigned long cur_freq;
 	unsigned long freq = ULONG_MAX;
@@ -152,17 +153,30 @@ int panthor_devfreq_init(struct panthor_device *ptdev)

 	ptdev->devfreq = pdevfreq;

-	ret = devm_pm_opp_set_regulators(dev, reg_names);
-	if (ret && ret != -ENODEV) {
-		if (ret != -EPROBE_DEFER)
-			DRM_DEV_ERROR(dev, "Couldn't set OPP regulators\n");
-		return ret;
+	/*
+	 * The power domain associated with the GPU may have already added an
+	 * OPP table, complete with OPPs, as part of the platform bus
+	 * initialization. If this is the case, the power domain is in charge of
+	 * also controlling the performance, with a set_performance callback.
+	 * Only add a new OPP table from DT if there isn't such a table present
+	 * already.
+	 */
+	table = dev_pm_opp_get_opp_table(dev);
+	if (IS_ERR_OR_NULL(table)) {
+		ret = devm_pm_opp_set_regulators(dev, reg_names);
+		if (ret && ret != -ENODEV) {
+			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;
+	} else {
+		dev_pm_opp_put_opp_table(table);
 	}

-	ret = devm_pm_opp_of_add_table(dev);
-	if (ret)
-		return ret;
-
 	spin_lock_init(&pdevfreq->lock);

 	panthor_devfreq_reset(pdevfreq);

-- 
2.51.0